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  • Body Composition and Athletic Performance: What Does the Science Actually Tell Us?

    Body Composition and Athletic Performance: What Does the Science Actually Tell Us?

    Body composition is often discussed as though there is a simple relationship between physique and performance.

    Athletes are told they should be leaner, lighter or more muscular, with the implication that changing body composition will automatically improve performance.

    The scientific literature does not support such a straightforward conclusion.

    Body composition is associated with athletic performance in some sporting contexts, but the strength and direction of that relationship vary according to the sport, the event, the athlete and the performance outcome being measured (Mathisen et al., 2023; Kettunen et al., 2025).

    More importantly, much of the literature describes associations between body composition and performance rather than demonstrating that deliberately changing body composition causes an improvement in performance (Mathisen et al., 2023).

    That distinction is important.

    So, what does the evidence actually tell us?

    What is body composition?

    Body composition refers to the different components that make up total body mass. In sports research, this commonly includes fat mass, fat-free mass and, where measurement methods allow, skeletal muscle and bone mineral components (Pettersson et al., 2024).

    This matters because two athletes can have the same body mass but substantially different amounts of fat and lean tissue.

    Likewise, athletes competing in different sports can have very different body-composition profiles while achieving high levels of performance.

    Recent research comparing endurance, strength and intermittent-sport athletes found distinct body-composition profiles between sporting disciplines, reinforcing the importance of considering body composition in relation to the demands of the sport rather than treating one physique as universally optimal (Sánchez-Oliver et al., 2025).

    The basic question is therefore not simply:

    “How much does the athlete weigh?”

    It is:

    “What does that body mass consist of, and how does it relate to the demands of the sport?”

    Why might body composition influence performance?

    There are several reasons why researchers have investigated body composition as a potential determinant of performance.

    In sports where athletes repeatedly move their own body mass, body mass and its composition may influence the physical demands of movement. In strength and power sports, lean tissue is relevant because skeletal muscle contributes to force production. These relationships mean that the balance between fat mass, lean mass and total body mass can be relevant to different sporting tasks (Pettersson et al., 2024; Mathisen et al., 2023).

    However, the importance of these relationships differs considerably between sports.

    For example, the demands placed on body mass during endurance running are different from those experienced by a rugby forward or an Olympic weightlifter. Consequently, the body composition associated with elite performance in one sport should not automatically be considered appropriate for another (Mathisen et al., 2023; Delany et al., 2025).

    Is lower body fat associated with better performance?

    There is evidence that lower levels of fat mass are associated with better performance in some endurance populations.

    A critical review of 29 longitudinal, prospective and intervention studies found that higher body-fat measures were negatively associated with performance in prolonged endurance events. However, the review also found that training variables and previous performance were sometimes equally or more important predictors of subsequent performance (Mathisen et al., 2023).

    More recent research supports the existence of an association, while also demonstrating why it should not be interpreted too simplistically.

    Kettunen et al. (2025) studied 52 elite endurance athletes and examined changes in body mass and body composition during different stages of the training season alongside endurance performance. The study investigated whether changes in body composition were associated with changes in performance rather than simply comparing athletes at one point in time.

    This type of longitudinal approach is useful because it provides more information than a simple cross-sectional comparison.

    However, it still does not establish that deliberately reducing fat mass will improve performance in every athlete.

    That distinction remains important.

    Lower body fat is not automatically better

    The evidence does not identify a universal body-fat percentage at which athletes become optimally conditioned for performance.

    In fact, the critical review by Mathisen et al. (2023) found no unique body-composition cut-off that could be used to signify a performance advantage.

    Research in volleyball provides a useful sport-specific example. A systematic review and meta-analysis found that body-fat levels differed according to sex but were not clearly associated with competitive level, leading the authors to conclude that relative body fat did not appear to be a strong indicator of performance level in competitive volleyball players (González-Ravé et al., 2023).

    This is an important counterpoint to the idea that lower body fat necessarily means better performance.

    The relationship may exist in some sporting contexts without being a universal predictor of sporting ability.

    Endurance sports may be different

    The evidence for a relationship between body composition and performance is arguably strongest in endurance sports.

    A 2024 observational study of 53 elite athletics competitors found that endurance athletes and power athletes displayed different body-composition profiles. Power athletes had greater body mass and fat-free mass, while endurance and power athletes showed different seasonal patterns of lean-mass changes (Pettersson et al., 2024).

    Importantly, the researchers did not observe significant reductions in whole-body fat mass or percentage body fat from the off-season to the in-season period across the athlete groups (Pettersson et al., 2024).

    This is an interesting finding because it demonstrates that elite athletes do not necessarily need to become progressively leaner during the transition into competition.

    In the same study, increases in lean mass were observed particularly among power athletes, while male endurance athletes also demonstrated an increase in lean mass across the season (Pettersson et al., 2024).

    This provides a useful reminder that athletic development does not always involve losing fat mass.

    What about muscle mass?

    The evidence for lean mass is also important.

    A critical review of body composition and performance found that increases in muscle mass were associated with favourable performance outcomes across a broader range of sports than the evidence for low body fat (Mathisen et al., 2023).

    However, it is important not to confuse an association between muscle mass and performance with proof that increasing muscle mass itself causes the improvement.

    Resistance training provides a good example.

    A 2024 systematic review examining resistance training in elite athletes reported improvements in sport-specific performance outcomes following resistance-training interventions (Makaruk et al., 2024).

    These improvements can occur alongside changes in muscle size, but resistance training produces numerous adaptations beyond hypertrophy, including changes in neural function, force production and power. Consequently, a performance improvement following resistance training cannot automatically be attributed to an increase in muscle mass alone (Makaruk et al., 2024).

    This distinction matters when interpreting body-composition research.

    Muscle mass may contribute to performance without being the sole cause of performance improvement.

    More muscle is not necessarily better

    It is tempting to assume that if muscle mass can contribute to performance, increasing it must always be beneficial.

    The evidence does not support that conclusion.

    Elite athletes competing in different events demonstrate different combinations of lean mass and fat mass. In the 2024 longitudinal athletics study, power athletes had greater fat-free mass than endurance athletes, while both groups demonstrated seasonal changes in lean mass (Pettersson et al., 2024).

    This suggests that the amount of lean mass required is influenced by the sporting event.

    A further consideration is that additional muscle also contributes to total body mass. Whether that additional mass is advantageous depends on the performance task and whether the increase in force or power sufficiently offsets any consequences associated with carrying additional mass (Mathisen et al., 2023).

    Therefore, the more useful concept is not simply “more muscle”, but “appropriate functional lean mass.”

    Strength and muscle mass are related — but not identical

    Recent research also highlights why muscle mass should not be treated as a direct substitute for strength.

    A 2025 study in collegiate athletes examined associations between muscle-mass measures obtained using DXA, bioelectrical impedance analysis and deuterated creatine dilution, and measures of muscular strength (Wilson et al., 2025).

    The study demonstrates that different approaches to estimating muscle mass can provide different information and that muscle mass is related to, but should not simply be equated with, muscular strength (Wilson et al., 2025).

    This has an important practical implication.

    If the performance outcome of interest is strength, then strength should actually be measured.

    If the outcome is sprinting, sprinting should be measured.

    If the outcome is jumping, jumping should be measured.

    Body composition may help explain performance characteristics, but it should not replace direct performance assessment.

    Body composition and football

    Football provides a particularly interesting example because players require a combination of physical qualities rather than one dominant attribute.

    Professional footballers need to perform high-intensity actions alongside prolonged intermittent activity, with physical demands varying according to position and playing role (Sebastiá-Rico et al., 2023a).

    A systematic review and meta-analysis examining professional male footballers found significant positional differences in several measures, including body mass, muscle mass and fat-free mass. However, there were no significant positional differences in several percentage-based measures, including percentage body fat and percentage muscle mass (Sebastiá-Rico et al., 2023a).

    This suggests that even within a single sport, body-composition characteristics are not necessarily uniform.

    It also challenges the idea that there should be a single body-composition target for every footballer.

    Measurement adds another layer of complexity

    A separate systematic review and meta-analysis involving 74 studies of professional male footballers found significant differences in reported fat mass, percentage body fat and fat-free mass depending on the assessment method and equation used (Sebastiá-Rico et al., 2023b).

    This is not a trivial methodological issue.

    If two methods produce different estimates, then comparing a player’s result against a published body-fat reference range requires knowledge of how the reference value was obtained.

    A 12% body-fat result obtained using one method should not necessarily be treated as directly equivalent to 12% obtained using another.

    Consequently, body-composition reference values should be interpreted in the context of the assessment method used (Sebastiá-Rico et al., 2023b).

    Body-composition measurements have error

    This issue extends beyond football.

    Body composition can be assessed using skinfolds, bioelectrical impedance, DXA and other techniques. These methods have different assumptions and sources of measurement error (Pettersson et al., 2024; Moon et al., 2023).

    A systematic review comparing DXA and bioelectrical impedance analysis in athletes found differences between the methods in estimates of body-composition compartments, demonstrating that they should not simply be regarded as interchangeable measurement techniques (Moon et al., 2023).

    The practical consequence is that small changes should be interpreted cautiously.

    The 2024 longitudinal athletics study provides a useful example. The researchers calculated the least significant change for their DXA measurements so that changes could be interpreted against the measurement precision of the equipment and protocol (Pettersson et al., 2024).

    This is a considerably more robust approach than assuming that every change in a body-composition number represents a genuine physiological adaptation.

    Does a lower body mass mean better performance?

    Not necessarily.

    A reduction in body mass can result from changes in fat mass, lean mass, water or combinations of these compartments.

    Therefore, the direction of change in body mass alone does not tell us whether the intervention was beneficial.

    This is particularly apparent when considering weight-category sports.

    Research on combat-sport athletes demonstrates that rapid weight loss is common, but the effects of rapid weight reduction on performance are not uniform across studies and appear to depend on factors including the magnitude of weight loss, timing and the recovery period available before competition (Barley et al., 2022; Pereira et al., 2023).

    A systematic review and meta-analysis found that rapid losses of up to approximately 5% body mass over less than seven days did not significantly impair some measures of physical performance in Olympic combat athletes (Barley et al., 2022).

    However, this should not be interpreted as evidence that rapid weight loss is harmless or that it is an appropriate strategy for all athletes.

    Other evidence has reported impairments in selected physiological and performance outcomes following rapid weight loss, with responses varying according to the protocol and outcome measured (Pereira et al., 2023).

    The literature therefore supports a more nuanced conclusion:

    weight loss does not have one predictable effect on performance.

    What happens when athletes manipulate body composition gradually?

    Gradual body-composition manipulation is different from rapid weight cutting.

    A 2025 scoping review examined 73 international consensus statements, position stands and practice guidelines relating to body-mass and body-composition manipulation in athletes. Across the literature, recommendations generally emphasised individualised targets based on sport, position, sex, age and competition phase, rather than universal body-composition targets (Delany et al., 2025).

    The review also found that relatively few of the guidance documents provided specific evidence-based targets for the magnitude, rate or timing of body-composition change, demonstrating that there remains substantial uncertainty in this area (Delany et al., 2025).

    This is important because practitioners sometimes present specific body-composition targets with considerably more certainty than the underlying evidence justifies.

    What about low energy availability?

    This is an important consideration, but it should be kept in context.

    Reducing body fat generally requires an energy deficit. If energy intake becomes insufficient relative to the demands of exercise and normal physiological function, low energy availability can occur.

    The IOC consensus literature identifies low energy availability as an important health and performance consideration when athletes manipulate body mass or composition (Mountjoy et al., 2023).

    However, this does not mean that all body-fat reduction is harmful.

    A controlled, appropriately planned change in body composition is fundamentally different from chronic under-fuelling.

    The 2025 scoping review of athlete body-composition recommendations found that current expert guidance generally emphasises gradual, individualised approaches that consider performance and health rather than simply maximising weight loss (Delany et al., 2025).

    Therefore, the relevant question is not whether an athlete is losing body fat.

    It is whether the process used to achieve that change is compatible with adequate nutrition, training and health.

    The role of nutrition

    Nutrition can influence body composition, but dietary changes do not necessarily produce predictable changes in athletic performance simply because they alter body mass.

    A 2025 review examining dietary practices, body composition and sports performance highlighted the interaction between dietary intake, body composition and performance, while also noting that nutritional strategies need to be considered in the context of the athlete and sporting demands (Gough, 2025).

    Similarly, a 2025 systematic review examining protein supplementation alongside endurance training found effects on some measures of body composition and physiological adaptation, illustrating that nutritional interventions can influence body-composition outcomes without necessarily producing uniform improvements across every performance measure (Sun et al., 2025).

    This reinforces an important point:

    body composition is an outcome influenced by nutrition and training, but changing body composition is not automatically synonymous with improving performance.

    Body composition may change without fat loss

    One of the more interesting findings from longitudinal athlete research is that changes in body composition do not necessarily follow the simple pattern of “less fat, more muscle”.

    Pettersson et al. (2024) followed elite endurance and power athletes across a competitive season and found meaningful increases in lean mass in many athletes, while there was no significant overall change in whole-body fat mass.

    Among male power athletes, body mass increased by approximately 1.4 kg, with a significant increase in lean mass of approximately 1.4 kg, while fat-mass variables did not significantly change (Pettersson et al., 2024).

    This is useful because it demonstrates that an increase in body mass can occur alongside favourable changes in body composition.

    In other words:

    A heavier athlete is not necessarily a less athletic athlete.

    The composition of the additional mass and its relationship with performance are what matter.

    Body composition versus performance: which matters more?

    This is arguably the most important question.

    The critical review by Mathisen et al. (2023) found that body-composition measures were associated with performance in several studies, particularly endurance performance. However, training variables such as training volume and speed, and previous performance, were sometimes equally or more important predictors of future performance.

    This finding is consistent with the broader sports-performance literature, where performance is influenced by multiple interacting physiological, technical and training variables (Sánchez-Oliver et al., 2025).

    A recent study comparing endurance, strength and intermittent athletes also demonstrated that athlete profiles differ across multiple dimensions, including body composition, diet, physical activity and other characteristics (Sánchez-Oliver et al., 2025).

    This makes it difficult — and probably inappropriate — to isolate body composition as a single determinant of performance.

    Association does not equal causation

    This is one of the biggest limitations of the current literature.

    Suppose elite athletes in a particular sport tend to have lower body-fat levels than recreational athletes.

    There are several possible explanations.

    Lower body fat may contribute to their performance.

    Alternatively, years of training may influence both their body composition and their performance.

    It is also possible that genetics, training history, sport selection and other physiological characteristics influence both variables.

    Cross-sectional research cannot fully distinguish between these explanations.

    Longitudinal research provides stronger evidence, but even longitudinal observational studies cannot necessarily establish that a change in body composition caused the change in performance.

    Intervention studies are therefore particularly valuable.

    However, the evidence base remains relatively small.

    The critical review by Mathisen et al. (2023) identified only 29 longitudinal, prospective or intervention studies specifically examining body composition and performance, with the majority involving endurance athletes.

    That is a relatively limited evidence base considering how frequently body-composition targets are used in sport.

    Is there an ideal body-fat percentage for athletes?

    Based on the current evidence, there is no scientifically defensible universal answer.

    Elite athletes demonstrate substantial variation in body composition across sports and positions (Sebastiá-Rico et al., 2023a; Pettersson et al., 2024).

    The methods used to measure body composition can also produce different estimates (Sebastiá-Rico et al., 2023b; Moon et al., 2023).

    And the available evidence does not identify a single body-composition threshold that consistently predicts superior performance (Mathisen et al., 2023).

    Therefore, a body-fat percentage should not automatically be interpreted as:

    good,
    bad,
    too high, or
    optimal.

    Its meaning depends on the individual athlete and the context in which it is being assessed.

    What about young athletes?

    This is an area where particular caution is required.

    Body composition changes naturally during growth and maturation, and adolescent athletes are not simply smaller versions of adult athletes.

    Consequently, adult body-composition targets should not be transferred directly to young athletes.

    The IOC body-composition recommendations specifically advise against routine body-composition assessment in athletes under 18 years of age, except where there is a clear justification and appropriate professional oversight (Mathisen et al., 2023).

    The rationale is not that body composition has no relevance to youth sport, but that the potential benefits of measurement need to be weighed against the risks associated with unnecessary focus on body weight and physique during a period of development (Mathisen et al., 2023).

    So, should athletes try to change their body composition?

    Sometimes.

    The evidence provides a reasonable rationale for body-composition manipulation when there is a clear relationship between the athlete’s current composition and the demands of their sport.

    For example, reducing excess fat mass may be useful where body mass has a meaningful effect on movement economy or performance.

    Increasing lean mass may be useful where additional muscle contributes to force and power production.

    But these are context-dependent decisions, not universal rules (Mathisen et al., 2023; Delany et al., 2025).

    The 2025 review of international recommendations concluded that body-composition goals should be individualised according to the athlete, sport, position, sex, age and competition phase (Delany et al., 2025).

    That is probably a more defensible approach than prescribing a particular body-fat percentage.

    How should body composition be interpreted?

    Body composition becomes much more useful when it is interpreted alongside actual performance.

    For example:

    Body composition changes + performance improves + health is maintained

    → potentially useful intervention.

    Body composition changes + performance does not improve

    → benefit is uncertain.

    Body composition changes + performance declines

    → the intervention may not have been worthwhile.

    This is not a formal evidence-based decision rule, but it reflects an important principle in performance practice: the purpose of changing body composition should ultimately be linked to the athlete’s sporting outcome rather than the body-composition number itself (Mathisen et al., 2023; Delany et al., 2025).

    What should practitioners monitor?

    There is no single assessment that can answer whether an athlete’s body composition is appropriate.

    Depending on the sport and athlete, useful information may include:

    • Body mass
    • Fat mass
    • Fat-free mass
    • Muscle mass
    • Strength
    • Power
    • Sprint performance
    • Jump performance
    • Endurance performance
    • Training load
    • Training availability
    • Recovery
    • Nutritional intake
    • Relevant health markers

    The reason for using multiple measures is straightforward: body composition and performance represent different constructs.

    A body-composition measurement can tell us something about the athlete’s physical makeup.

    A sprint test tells us about sprint performance.

    A strength test tells us about strength.

    A match-performance measure tells us something about sporting performance.

    None should automatically be used as a substitute for another.

    A non-biased conclusion

    So, where does the evidence leave us?

    The claim that “leaner is always better” is not supported by the current literature.

    There is evidence that higher fat mass is associated with poorer endurance performance in some populations, and there is evidence that lean mass is positively associated with performance characteristics in a number of sporting contexts (Mathisen et al., 2023; Pettersson et al., 2024).

    However, these relationships are not universal.

    Professional footballers demonstrate different body-composition characteristics between positions, but not all percentage-based measures differ between positions (Sebastiá-Rico et al., 2023a).

    Competitive volleyball research has found that relative body fat does not appear to be a strong indicator of competitive level (González-Ravé et al., 2023).

    Elite endurance and power athletes also demonstrate different body-composition profiles and seasonal adaptations, with changes in lean mass occurring without significant reductions in overall fat mass in a recent longitudinal study (Pettersson et al., 2024).

    The evidence also demonstrates that measurement method matters, with different techniques producing different estimates of body-composition compartments (Moon et al., 2023; Sebastiá-Rico et al., 2023b).

    Perhaps most importantly, the evidence base directly testing whether deliberate body-composition manipulation improves sporting performance remains relatively limited (Mathisen et al., 2023).

    Therefore, the most defensible conclusion is:

    Body composition can influence athletic performance, but there is no single body composition that defines an optimal athlete.

    For some athletes, reducing fat mass may improve performance.

    For others, increasing lean mass may be beneficial.

    For others, maintaining body composition may be the most appropriate strategy.

    And for some athletes, attempting to change body composition may offer little performance benefit while introducing unnecessary nutritional or health challenges (Delany et al., 2025; Mountjoy et al., 2023).

    The question should therefore not simply be:

    “How lean should an athlete be?”

    or:

    “What should this athlete weigh?”

    A better question is:

    “Is this athlete’s current body composition limiting performance, and is there good evidence that changing it will make them better?”

    That question places body composition where it belongs:

    as one component of performance, rather than the definition of performance itself.

    Key takeaways

    1. Body composition is associated with athletic performance, but the relationship is highly dependent on the sport, event and athlete (Mathisen et al., 2023; Pettersson et al., 2024).

    2. Higher body-fat measures are associated with poorer endurance performance in some populations, but this does not establish a universal optimal body-fat percentage (Mathisen et al., 2023; Kettunen et al., 2025).

    3. Lean mass is associated with performance characteristics such as strength and power, but increasing muscle mass is not automatically responsible for performance improvements (Makaruk et al., 2024; Wilson et al., 2025).

    4. Professional footballers demonstrate positional differences in some body-composition measures, but not all measures differ between positions (Sebastiá-Rico et al., 2023a).

    5. Different body-composition assessment methods can produce different results, meaning reference values should be interpreted alongside the method used (Moon et al., 2023; Sebastiá-Rico et al., 2023b).

    6. Elite athletes can increase lean mass during a competitive season without necessarily reducing whole-body fat mass (Pettersson et al., 2024).

    7. Evidence from weight-category sports suggests that the performance consequences of weight loss depend on the magnitude, method and timing of the intervention (Barley et al., 2022; Pereira et al., 2023).

    8. Current international guidance supports individualised rather than universal body-composition targets (Delany et al., 2025).

    9. Much of the body-composition/performance literature is observational, so association should not automatically be interpreted as causation (Mathisen et al., 2023).

    10. The most useful body-composition target is therefore not necessarily the leanest or lightest physique, but the composition that supports the athlete’s specific performance demands while maintaining training capacity and health (Delany et al., 2025).

    References

    Barley, O.R., Chapman, D.W., Guppy, S.N. and Abbiss, C.R. (2022) ‘Rapid weight loss of up to five percent of the body mass in less than 7 days does not affect physical performance in official Olympic combat athletes with weight classes: a systematic review with meta-analysis’, Sports Medicine, 52, pp. 2527–2541.

    Delany, L.V., Costello, N., Jones, B. and Backhouse, S.H. (2025) ‘Dietary recommendations for body mass and composition manipulation in male and female athletes: a scoping review of consensus statements, position stands and practice guidelines from international expert groups’, Sports Medicine, 55, pp. 2445–2487. doi:10.1007/s40279-025-02285-4.

    González-Ravé, J.M., et al. (2023) ‘Body fat of competitive volleyball players: a systematic review with meta-analysis’, Sports Medicine – Open, 9.

    Gough, L.A. (2025) ‘Dietary practices, body composition, and sports performance of athletes’, Nutrients, 17(19), 3102. doi:10.3390/nu17193102.

    Kettunen, O., Mikkola, J. and Ihalainen, J.K. (2025) ‘Associations between body composition and performance in elite endurance athletes’, International Journal of Sports Physiology and Performance, 20(11), pp. 1530–1537. doi:10.1123/ijspp.2024-0506.

    Makaruk, H., Starzak, M., Tarkowski, P., Sadowski, J. and Winchester, J. (2024) ‘The effects of resistance training on sport-specific performance of elite athletes: a systematic review with meta-analysis’, Journal of Human Kinetics, 91, pp. 135–155. doi:10.5114/jhk/185877.

    Mathisen, T.F., Ackland, T., Burke, L.M. et al. (2023) ‘Best practice recommendations for body composition considerations in sport to reduce health and performance risks: a critical review, original survey and expert opinion by a subgroup of the IOC consensus on Relative Energy Deficiency in Sport (REDs)’, British Journal of Sports Medicine, 57(17), pp. 1148–1158. doi:10.1136/bjsports-2023-106812.

    Moon, J.R., et al. (2023) ‘Agreement between dual-energy X-ray absorptiometry and bioelectrical impedance analysis for assessing body composition in athletes: a systematic review and meta-analysis’, Journal of Functional Morphology and Kinesiology, 8.

    Mountjoy, M., Sundgot-Borgen, J., Burke, L. et al. (2023) ‘2023 International Olympic Committee’s consensus statement on Relative Energy Deficiency in Sport (REDs)’, British Journal of Sports Medicine, 57(17), pp. 1073–1097. doi:10.1136/bjsports-2023-106994.

    Pereira, R., et al. (2023) ‘Effects of different rapid weight loss strategies and percentages on performance-related parameters in combat sports: an updated systematic review’, Sports, 11(3), 60. doi:10.3390/sports11030060.

    Pettersson, S., Kalén, A., Gustafsson, M., Grau, S. and Caspers, A. (2024) ‘Off- to in-season body composition adaptations in elite male and female endurance and power event athletics competitors: an observational study’, BMC Sports Science, Medicine and Rehabilitation, 16, 90. doi:10.1186/s13102-024-00877-7.

    Sánchez-Oliver, A.J., et al. (2025) ‘Multidimensional differences between athletes of endurance, strength, and intermittent sports: body composition, diet, resting metabolic rate, physical activity, sleep quality, and subjective well-being’, Nutrients, 17(7), 1172. doi:10.3390/nu17071172.

    Sebastiá-Rico, J., Soriano, J.M., González-Gálvez, N. and Martínez-Sanz, J.M. (2023a) ‘Differences in body composition between playing positions in men’s professional soccer: a systematic review with meta-analysis’, Applied Sciences, 13(8), 4782. doi:10.3390/app13084782.

    Sebastiá-Rico, J., Soriano, J.M., González-Gálvez, N. and Martínez-Sanz, J.M. (2023b) ‘Body composition of male professional soccer players using different measurement methods: a systematic review and meta-analysis’, Nutrients, 15(5), 1160. doi:10.3390/nu15051160.

    Sun, W., et al. (2025) ‘Effects of protein supplementation on body composition, physiological adaptations, and performance during endurance training: a systematic review and meta-analysis’, Frontiers in Nutrition, 12.

    Wilson, M.M., et al. (2025) ‘Association of body composition measures to muscle strength using DXA, D3Cr, and BIA in collegiate athletes’, Scientific Reports, 15.

    What the evidence means in practice

    The literature supports a performance-led rather than physique-led approach to body composition.

    The strongest evidence does not suggest that athletes should be pushed towards a universal body-fat percentage. Instead, body composition should be interpreted in relation to the demands of the sport, the athlete’s individual characteristics, objective performance and longitudinal change (Mathisen et al., 2023; Delany et al., 2025).

    The evidence is also stronger for some relationships than others. The association between lower fat mass and endurance performance is reasonably consistent in relevant populations, whereas evidence that deliberately reducing fat mass improves performance in an individual athlete is considerably less extensive (Mathisen et al., 2023; Kettunen et al., 2025).

    Similarly, greater lean mass appears relevant to strength and power performance, but the performance benefits of resistance training cannot simply be attributed to muscle hypertrophy (Makaruk et al., 2024; Wilson et al., 2025).

    Finally, measurement error should not be ignored. Different assessment techniques can generate different estimates, while longitudinal DXA research demonstrates the value of considering the least significant change before interpreting a small change as physiologically meaningful (Moon et al., 2023; Pettersson et al., 2024).

    The evidence therefore supports a relatively simple principle:

    Don’t optimise body composition for its own sake. Optimise it only when there is a clear, evidence-informed reason to believe that doing so will improve the athlete’s performance.

  • Injury Recovery Nutrition: How to Recover Faster From Injury

    Injury Recovery Nutrition: How to Recover Faster From Injury

    Injury recovery isn’t just about rehabilitation and training load. Injury recovery nutrition plays a critical role in how effectively tissues repair, remodel and return to function.

    Despite this, many athletes underfuel or prioritise the wrong nutritional strategies during injury, ultimately slowing recovery and delaying return to play.

    This article outlines evidence-based injury recovery nutrition strategies to support faster and more effective rehabilitation.

    Energy Intake in Injury Recovery Nutrition

    One of the most common mistakes during injury is reducing calorie intake too aggressively.

    Although training volume may decrease, injury increases metabolic demand due to:

    • Tissue repair
    • Inflammatory processes
    • Immune system activation

    Inadequate energy intake has been shown to delay recovery, increase muscle loss and impair immune function (Kozjek, Tonin & Gleeson, 2025) 

    Key takeaway:

    Maintain adequate energy intake avoid underfueling during injury.

    Protein Intake for Injury Recovery

    Protein is one of the most important components of injury recovery nutrition.

    It supports:

    • Muscle repair
    • Collagen synthesis
    • Tissue regeneration

    Research highlights the importance of maintaining adequate protein intake during injury rehabilitation to preserve muscle mass and support healing (Giraldo‑Vallejo et al., 2023)

    Practical guidelines:

    • 1.6–2.2 g/kg/day
    • 20–40g per meal
    • Even distribution across the day

    Collagen and Connective Tissue Repair

    Connective tissues (tendons, ligaments and cartilage) rely heavily on collagen.

    Research shows:

    • Collagen supplementation combined with training may improve tendon structure in some cases (Buchalski et al., 2026) 
    • However, results remain inconsistent across studies (Kirmse et al., 2024) 

    Key takeaway:

    Collagen can support connective tissue recovery, but should be used alongside a structured rehab programme.

    Inflammation and Recovery Nutrition

    Inflammation is a normal and necessary part of the healing process.

    However:

    • Too much inflammation can delay recovery
    • Too little can impair healing

    Omega-3 fatty acids have been shown to influence inflammatory markers and oxidative stress, although results are mixed (Fernández‑Lázaro et al., 2024) 

    Practical takeaway:

    • Include omega-3-rich foods (e.g. oily fish)
    • Avoid aggressively suppressing inflammation

    Micronutrients in Injury Recovery Nutrition

    Micronutrients are essential in injury recovery, particularly for bone healing.

    Key nutrients include:

    • Vitamin D
    • Calcium
    • Magnesium
    • Vitamin K

    Deficiencies are associated with slower bone regeneration and reduced recovery capacity (Prakash et al., 2024)

    Research also suggests that overall diet quality is more important than isolated supplementation (Papadopoulou et al., 2022) 

    Key takeaway:

    Focus on a nutrient-dense, whole-food-based diet.

    Individualised Nutrition for Injury Recovery

    There is no one-size-fits-all approach to injury recovery nutrition.

    Strategies must adapt based on:

    • Injury type
    • Stage of recovery
    • Training and rehab demands

    Evidence consistently highlights the need for individualised nutrition interventions during rehabilitation (Giraldo‑Vallejo et al., 2023) 

    Key Takeaways for Injury Recovery Nutrition

    • Maintain energy intake
    • Prioritise protein
    • Support connective tissue when needed
    • Manage (not eliminate) inflammation
    • Ensure micronutrient adequacy
    • Individualise nutritional strategies

    Injury Recovery Nutrition System (Practical Application)

    If you want to apply injury recovery nutrition properly without guesswork I’ve put everything into a structured Injury Nutrition Recovery System.

    It includes 5 easy to use guides covering.

    • Concussion
    • Soft tissue injuries
    • Tendon & ligament injuries
    • Cartilage & joint issues
    • Fracture recovery

    Each guide provides:

    • Clear nutrition targets
    • Practical food strategies
    • Supplement guidance
    • Real-world application

    View the full system here:

    https://cc-nutrition.co.uk/product/injury-recovery-nutrition-system/

    Final Thoughts on Injury Recovery Nutrition

    Nutrition will not replace rehabilitation but without it, recovery is often slower, less effective and less predictable.

    Optimising injury recovery nutrition is one of the simplest ways to improve outcomes and return to play in a stronger position.

    Related articles:

    https://cc-nutrition.co.uk/2026/06/23/electrolytes-in-football/

    https://cc-nutrition.co.uk/2026/06/20/youth-football-nutrition-guide-parents-performance-fuel-recovery/

    https://cc-nutrition.co.uk/2026/06/18/creatine-male-female-athletes-evidence-based-performance-review/

    https://cc-nutrition.co.uk/2026/06/11/sleep-optimisation-athletes/

  • Parent Football Nutrition Guide: Fuelling Young Players Effectively

    Parent Football Nutrition Guide: Fuelling Young Players Effectively

    Youth football nutrition plays a key role in energy levels, recovery, focus, and consistency across the training week. Many young players are not underperforming because of fitness or talent, but because of inconsistent fuelling and hydration patterns across the day. This guide explains how parents can support practical, realistic nutrition habits that directly improve performance, recovery, and wellbeing.

    Why youth football nutrition matters

    Football is a high-intensity intermittent sport involving repeated sprints, rapid changes of direction, physical contact, and constant decision-making under fatigue. These actions rely heavily on muscle glycogen, the body’s stored form of carbohydrate. When glycogen levels drop, performance declines, particularly in repeated sprint ability and late-game intensity (Bangsbo et al., 2006; Burke et al., 2011). This often presents as players starting strongly but fading in the second half, reduced reaction speed, and slower decision-making under pressure.

    In children and adolescents, this is compounded by growth demands, meaning energy is also required for:

    • Muscle repair and adaptation
    • Bone growth
    • Hormonal development
    • Cognitive function

    (Gibson et al., 2011)

    1. Pre-training and pre-match nutrition (football pre match meal)

    The goal before football is to ensure sufficient carbohydrate availability to support high-intensity performance throughout the session or match (Burke et al., 2011). Think of this as “fuel loading” rather than just eating to stop hunger.

    2–3 hours before training or match (main meal)

    This meal should:

    • Top up carbohydrate stores (main fuel source)
    • Provide moderate protein for muscle support
    • Be low in fat and easy to digest

    Examples:

    • Pasta with chicken in tomato sauce
    • Rice with chicken or turkey
    • Wraps with chicken and light sauce + fruit
    • Cereal with milk, banana, and yoghurt
    • Toast with scrambled eggs and fruit juice

    Avoid meals that are too light (e.g. fruit or yogurt alone), as they do not provide enough energy for high-intensity performance.

    30–60 minutes before exercise (optional snack)

    Useful if there is a long gap since the last meal or the player feels hungry.

    Examples:

    • Banana
    • Cereal bar
    • Yogurt pouch
    • Toast with honey

    This helps maintain blood glucose availability early in exercise (Jeukendrup, 2014).

    2. Hydration for young footballers

    Even mild dehydration can reduce reaction time, concentration, and endurance performance (Thomas et al., 2016). Children are especially vulnerable because they often:

    • Forget to drink during school
    • Don’t recognise early thirst
    • Become distracted during play

    Practical approach:

    • Encourage regular drinking throughout the day
    • Use small, frequent sips during training
    • Rehydrate after sessions at home

    Simple check:

    • Pale yellow urine usually indicates good hydration status

    3. During training and matches

    For most youth football sessions under 90 minutes:

    • Water is sufficient
    • No structured fuelling is needed

    For tournaments or hot conditions:

    • Hydration becomes more important
    • Fluid loss can significantly impact later performance

    A common issue is performance drop-off in later games due to cumulative dehydration and reduced energy availability (Burke et al., 2011).

    4. Football recovery nutrition (post training nutrition)

    Recovery is where many young players lose performance consistency without realising it. After football, the body needs to:

    • Refill muscle glycogen
    • Repair muscle tissue
    • Restore fluid balance

    Recovery is most effective when nutrition is consumed within 1–2 hours post exercise (Burke et al., 2017).

    Best recovery approach: carbohydrate + protein

    Examples:

    • Chicken and rice
    • Tuna sandwich + fruit + yogurt
    • Milk smoothie with banana and oats
    • Eggs on toast + milk
    • Yogurt with granola and berries

    Poor recovery nutrition can lead to:

    • Increased fatigue
    • Reduced performance in next session
    • Slower weekly recovery cycle

    5. Daily youth athlete nutrition habits

    Consistency across the week is more important than match-day nutrition strategies (Desbrow et al., 2014).

    Key habits:

    • Eat breakfast every day
    • Avoid long gaps between meals
    • Include carbohydrates at most meals
    • Include protein for growth and repair
    • Eat fruit and vegetables daily
    • Maintain regular hydration

    Many young athletes under-fuel during school hours, which reduces evening training quality (Gibson et al., 2011).

    6. Travel nutrition for football matches

    Away games often disrupt normal eating routines, which can negatively affect performance (Burke et al., 2011).

    Common issues:

    • Missed meals before travel
    • Long gaps without food
    • Reliance on convenience snacks
    • Nervous appetite suppression

    Practical strategy:

    • Eat a carbohydrate-based meal before leaving home
    • Bring familiar, easy-to-eat foods

    Examples:

    • Sandwiches
    • Fruit
    • Cereal bars
    • Yogurts
    • Water

    Avoid relying on unfamiliar venue food options.

    7. Common youth football nutrition mistakes

    • Under-fuelling disguised as “healthy eating” (fruit or yogurt alone is not enough energy)
    • Skipping recovery meals after training (reduces glycogen restoration)
    • Hydration only on match days rather than daily
    • Over-reliance on supplements instead of food-first nutrition (Thomas et al., 2016)

    8. Warning signs of poor football nutrition

    Look for:

    • Early fatigue in training
    • Drop-off in second-half performance
    • Poor concentration late in sessions
    • Slow recovery between training days
    • Frequent minor illness
    • Heavy legs during warm-ups

    These are often nutrition-related rather than fitness-related (Gibson et al., 2011).

    9. Energy availability and development

    Energy availability is the energy left after exercise that supports growth and normal body function.

    Low energy availability can affect:

    • Growth and development
    • Bone health
    • Recovery capacity
    • Injury risk
    • Training adaptation

    (Gibson et al., 2011; Thomas et al., 2016)

    This usually develops gradually through small daily deficits rather than intentional restriction.

    Conclusion

    Effective youth football nutrition is built on:

    • Adequate fuelling before activity (Burke et al., 2011)
    • Consistent hydration habits (Thomas et al., 2016)
    • Structured recovery nutrition (Burke et al., 2017)

    Small improvements in these areas can significantly improve performance, recovery, and enjoyment of football.

    Final note for parents

    Every young footballer is different, and nutrition needs vary based on training load, growth stage, and individual response. If you are unsure whether your child is fuelling correctly for football, or you would like personalised support tailored to their schedule and development, you can get in touch for expert nutrition guidance.

    Contact me

  • The Truth About Electrolyte Supplements: Are They Necessary for Performance, Hydration and Recovery? An Evidence-Based Review

    The Truth About Electrolyte Supplements: Are They Necessary for Performance, Hydration and Recovery? An Evidence-Based Review

    Introduction

    Electrolyte supplements have become one of the fastest-growing sectors within the sports nutrition industry. Powders, tablets and ready-to-drink beverages are widely marketed as essential tools for improving hydration, preventing muscle cramps, enhancing endurance performance and accelerating recovery. Social media and commercial marketing often portray electrolyte supplementation as a universal requirement for anyone engaging in exercise, regardless of duration, intensity or environmental conditions.

    However, the peer-reviewed evidence presents a more nuanced picture. The physiological requirement for electrolyte supplementation is highly context-dependent and influenced by factors including exercise duration, environmental conditions, individual sweat rates, sweat sodium concentration, training status and nutritional intake (Sawka et al., 2007; Casa et al., 2019). While some athletes, particularly endurance competitors and those training in hot environments, may derive significant benefits from targeted sodium replacement strategies, routine electrolyte supplementation is often unnecessary for recreational exercisers undertaking short-duration activities.

    The purpose of this article is to critically evaluate the scientific evidence surrounding electrolyte supplementation, examining its physiological rationale, effects on hydration and performance, role in recovery and cramp prevention, and practical applications within athletic populations.

    What Are Electrolytes?

    Electrolytes are minerals that dissociate into electrically charged ions when dissolved in water. They are essential for maintaining cellular homeostasis and supporting multiple physiological systems that underpin athletic performance. The principal electrolytes relevant to exercise include sodium (Na⁺), potassium (K⁺), chloride (Cl⁻), magnesium (Mg²⁺) and calcium (Ca²⁺) (Shirreffs and Sawka, 2011).

    Each electrolyte performs distinct physiological functions.

    Sodium

    Sodium is the major extracellular cation and the most important electrolyte lost through sweat. It regulates:

    • Plasma osmolality

    • Extracellular fluid balance

    • Blood pressure regulation

    • Intestinal absorption of nutrients and water

    • Nerve impulse transmission

    • Muscle contraction

    • Thirst mechanisms

    Approximately 90–95% of extracellular osmotic pressure is determined by sodium concentration (Sawka et al., 2007). Consequently, disturbances in sodium balance have substantial implications for hydration status, cardiovascular function and thermoregulation.

    Potassium

    Potassium is the principal intracellular cation and is critical for:

    • Maintenance of membrane potential

    • Skeletal muscle contraction

    • Cardiac electrical activity

    • Glycogen synthesis

    • Acid-base regulation

    Despite its physiological importance, sweat potassium losses are relatively modest and are generally replaced through habitual dietary intake (Shirreffs and Sawka, 2011).

    Magnesium

    Magnesium serves as a cofactor in over 300 enzymatic reactions and is involved in:

    • ATP production

    • Protein synthesis

    • Muscle contraction and relaxation

    • Neuromuscular transmission

    • Regulation of inflammation and oxidative stress

    Magnesium deficiency can impair physical performance and recovery; however, deficiencies are relatively uncommon in well-nourished athletic populations (Grgic and Pickering, 2019).

    Calcium

    Calcium is essential for:

    • Excitation-contraction coupling

    • Muscle contraction

    • Bone metabolism

    • Blood coagulation

    • Cellular signalling

    Although calcium losses occur through sweat, exercise-induced deficiencies are uncommon in athletes consuming adequate dietary calcium (Shirreffs and Sawka, 2011).

    Why Sodium Is the Most Important Exercise Electrolyte

    Although commercial electrolyte products frequently emphasise multiple minerals, the scientific literature overwhelmingly identifies sodium as the primary electrolyte of concern during exercise (Sawka et al., 2007; Baker et al., 2016).

    During exercise, sweating serves as the body’s primary mechanism for dissipating heat generated by muscular contractions. Evaporation of sweat removes heat from the skin surface and prevents excessive increases in core temperature. However, sweating also results in substantial losses of water and sodium.

    Sweat sodium concentrations demonstrate considerable inter-individual variability.

    Baker et al. (2016) analysed over 500 athletes and reported sweat sodium concentrations ranging from approximately 10 mmol·L⁻¹ to over 90 mmol·L⁻¹. Similarly, whole-body sweat rates ranged from less than 0.5 L·h⁻¹ to more than 2.5 L·h⁻¹.

    Consequently, two athletes performing identical exercise in the same environmental conditions may experience dramatically different sodium losses.

    For example:

    Athlete A:

    • Sweat rate: 0.8 L·h⁻¹

    • Sweat sodium: 30 mmol·L⁻¹

    • Sodium loss: approximately 550 mg·h⁻¹

    Athlete B:

    • Sweat rate: 2.0 L·h⁻¹

    • Sweat sodium: 70 mmol·L⁻¹

    • Sodium loss: approximately 3,200 mg·h⁻¹

    During a three-hour endurance event, Athlete B could lose almost 10 g of sodium, equivalent to approximately 25 g of table salt.

    These differences explain why some athletes develop symptoms of excessive sodium depletion whereas others can perform successfully with minimal electrolyte replacement.

    Why Do Sweat Sodium Losses Differ Between Athletes?

    Several factors influence sweat sodium concentration.

    Genetics

    Research suggests that genetic variation influences sweat gland function and sodium reabsorption (Baker et al., 2016). Some individuals are naturally high sodium sweaters.

    Heat Acclimation

    Repeated exposure to hot environments increases aldosterone secretion, enhancing sodium reabsorption within sweat glands and reducing sodium losses (Périard et al., 2015).

    Exercise Intensity

    Higher exercise intensities increase metabolic heat production and sweating rates, potentially increasing total sodium losses.

    Training Status

    Well-trained athletes often demonstrate improved thermoregulatory efficiency and more effective sodium conservation mechanisms.

    Sex Differences

    Emerging evidence suggests potential sex differences in sweating responses. Females generally exhibit lower sweat rates and may lose less sodium than males during comparable exercise intensities, although considerable individual variability exists (Baker et al., 2020).

    These findings reinforce the principle that hydration strategies should be individualised rather than universally prescribed.

    Electrolytes and the Physiology of Hydration

    Hydration involves more than replacing water losses.

    Body water is distributed between intracellular and extracellular compartments. Sodium is the principal determinant of extracellular fluid osmolality and governs water movement between these compartments.

    When sweat losses occur:

    • Plasma volume decreases.

    • Blood viscosity increases.

    • Stroke volume decreases.

    • Heart rate increases.

    • Skin blood flow becomes compromised.

    • Thermoregulatory capacity declines.

    • Perceived exertion increases.

    • Exercise performance may deteriorate.

    These responses collectively contribute to cardiovascular drift and reduced endurance capacity (Sawka et al., 2007).

    The importance of sodium replacement lies in its ability to facilitate restoration of extracellular fluid balance.

    Sodium ingestion:

    • Stimulates thirst

    • Enhances intestinal water absorption via sodium-glucose co-transport mechanisms

    • Increases fluid retention

    • Reduces urinary losses

    • Supports plasma volume restoration

    Shirreffs and Maughan (1998) demonstrated that beverages containing sodium promoted significantly greater fluid retention than plain water following exercise-induced dehydration. Participants consuming plain water rapidly produced dilute urine and failed to fully restore fluid balance.

    Similarly, Evans et al. (2017) reported that sodium-containing beverages improve post-exercise rehydration by maintaining plasma osmolality and reducing diuresis.

    Therefore, sodium functions not merely as an electrolyte but as a key regulator of effective rehydration.

    Does Electrolyte Supplementation Improve Performance?

    The answer depends upon exercise conditions.

    The scientific literature does not support the notion that electrolyte supplementation acts as a direct ergogenic aid similar to caffeine, creatine or dietary nitrate.

    Instead, electrolyte supplementation primarily supports performance indirectly through preservation of hydration status.

    Exercise Lasting Less Than 60–90 Minutes

    The ACSM Position Stand concludes that electrolyte supplementation is generally unnecessary during exercise lasting less than 60–90 minutes under temperate conditions (Sawka et al., 2007).

    Most individuals possess sufficient fluid and electrolyte reserves to complete these activities without performance impairment.

    Prolonged Exercise

    During endurance exercise exceeding two hours, substantial sweat losses may compromise cardiovascular function.

    Meta-analytic evidence indicates that dehydration exceeding approximately 2% of body mass can negatively affect endurance performance, particularly in hot environments (Goulet, 2012).

    Maintaining plasma volume through appropriate fluid and sodium replacement may therefore preserve:

    • Stroke volume

    • Cardiac output

    • Skin blood flow

    • Thermoregulation

    • Exercise capacity

    McCubbin et al. (2019) concluded that sodium supplementation appears particularly beneficial for athletes with:

    • High sweat rates

    • High sweat sodium concentrations

    • Long-duration exercise

    • Multiple training sessions

    • Hot environmental conditions

    However, evidence that electrolyte supplementation enhances performance in already euhydrated athletes remains limited.

    Electrolytes and Muscle Cramps: Separating Myth from Science

    The belief that muscle cramps result primarily from electrolyte depletion has persisted for decades.

    Early observations noted that industrial workers performing heavy labour in hot environments frequently developed muscle cramps following substantial sweat losses (Bergeron, 2008).

    However, contemporary evidence has challenged this explanation.

    Schwellnus et al. (2011) proposed the altered neuromuscular control theory, suggesting that exercise-associated muscle cramps result primarily from:

    • Fatigue-induced increases in muscle spindle activity

    • Reduced Golgi tendon organ inhibition

    • Increased alpha motor neuron excitability

    • Abnormal reflex control

    Several studies have failed to demonstrate consistent differences in plasma electrolyte concentrations between athletes who cramp and those who do not.

    Consequently, electrolyte depletion cannot be considered the sole cause of exercise-associated muscle cramps.

    Nevertheless, sodium depletion may contribute in susceptible individuals, particularly during prolonged exercise in hot environments accompanied by substantial sweat losses.

    Therefore, electrolyte supplementation may reduce cramp incidence in specific athletes but cannot be considered a universal preventive strategy.

    Exercise-Associated Hyponatraemia: The Hidden Danger

    Perhaps the strongest scientific rationale for appropriate electrolyte strategies is the prevention of exercise-associated hyponatraemia (EAH).

    EAH is defined as plasma sodium concentrations below 135 mmol·L⁻¹ occurring during or immediately following exercise (Hew-Butler et al., 2015).

    EAH has been documented in:

    • Marathon runners

    • Triathletes

    • Ironman competitors

    • Military personnel

    • Ultra-endurance athletes

    • Recreational participants

    Symptoms include:

    • Nausea

    • Headache

    • Confusion

    • Vomiting

    • Seizures

    • Cerebral oedema

    • Death

    Importantly, the primary cause of EAH is excessive fluid intake rather than sodium loss alone.

    Athletes who consume fluids beyond thirst can dilute plasma sodium concentrations despite taking electrolyte supplements.

    Current recommendations therefore emphasise:

    • Drinking according to thirst

    • Monitoring body mass changes

    • Individualising fluid plans

    • Avoiding overconsumption of fluids

    • Replacing sodium strategically during prolonged exercise

    (Casa et al., 2019; Hew-Butler et al., 2015).

    The Commercialisation of Electrolytes: Are They Overmarketed?

    The global electrolyte market has expanded dramatically, driven by messaging suggesting that virtually everyone requires electrolyte supplementation.

    However, peer-reviewed evidence suggests this narrative is often exaggerated.

    Most recreational exercise:

    • Lasts less than one hour

    • Produces modest sweat losses

    • Occurs in temperate conditions

    • Can be adequately supported through normal dietary intake and water consumption

    Western diets generally provide sodium intakes well above physiological requirements (World Health Organization, 2012).

    Consequently, many consumers purchasing electrolyte products are unlikely to derive measurable performance benefits.

    This does not mean electrolyte products are ineffective. Rather, their utility should be considered context-specific and individualised rather than universally prescribed.

    Practical Recommendations for Sports Nutrition Practitioners

    Electrolyte supplementation should be considered when:

    • Exercise duration exceeds two hours.

    • Sweat losses exceed 2% of body mass.

    • Athletes train in hot and humid environments.

    • Multiple daily sessions are performed.

    • Athletes exhibit visible salt residue on clothing.

    • Sweat testing identifies high sodium losses.

    • Previous episodes of hyponatraemia or severe cramping have occurred.

    Electrolyte supplementation is generally unnecessary when:

    • Exercise duration is less than 60–90 minutes.

    • Sweat losses are modest.

    • Training occurs in cool environments.

    • Normal dietary intake is adequate.

    • Recreational exercise is performed at low-to-moderate intensity.

    Conclusion

    The truth about electrolyte supplements is considerably more complex than contemporary marketing suggests. Electrolyte supplementation is not universally necessary and should not be viewed as a performance-enhancing intervention in its own right. Rather, its benefits arise primarily from supporting fluid balance, maintaining plasma volume and reducing physiological strain during prolonged exercise and substantial sweat losses.

    For most recreational exercisers, water and a balanced diet are sufficient. However, endurance athletes, team sport players undertaking repeated sessions and high sodium sweaters competing in challenging environmental conditions may derive meaningful benefits from carefully planned sodium replacement strategies.

    Ultimately, evidence-based sports nutrition practice supports an individualised approach in which electrolyte supplementation is prescribed according to physiology, exercise demands and environmental context rather than commercial trends.

    References

    Baker, L.B., Barnes, K.A., Anderson, M.L., Passe, D.H. and Stofan, J.R. (2016) ‘Normative data for regional sweat sodium concentration and whole-body sweating rate in athletes’, Journal of Sports Sciences, 34(4), pp. 358–368. doi:10.1080/02640414.2015.1055291.

    Bergeron, M.F. (2008) ‘Muscle cramps during exercise – is it fatigue or electrolyte deficit?’, Current Sports Medicine Reports, 7(Suppl. 4), pp. S50–S55. doi:10.1249/JSR.0b013e31817ef700.

    Casa, D.J., Stearns, R.L., Lopez, R.M., Ganio, M.S., McDermott, B.P., Walker Yeargin, S., Yamamoto, L.M., Mazerolle, S.M., Roti, M.W., Armstrong, L.E. and Maresh, C.M. (2019) ‘National Athletic Trainers’ Association position statement: Fluid replacement for the physically active’, Journal of Athletic Training, 54(7), pp. 814–835. doi:10.4085/1062-6050-484-17.

    Evans, G.H., James, L.J., Shirreffs, S.M. and Maughan, R.J. (2017) ‘Optimizing the restoration and maintenance of fluid balance after exercise-induced dehydration’, Journal of Applied Physiology, 122(4), pp. 945–951. doi:10.1152/japplphysiol.00745.2016.

    Goulet, E.D.B. (2012) ‘Effect of exercise-induced dehydration on endurance performance: Evaluating the impact of exercise protocols on outcomes using a meta-analytic procedure’, British Journal of Sports Medicine, 47(11), pp. 679–686. doi:10.1136/bjsports-2012-090958.

    Grgic, J. and Pickering, C. (2019) ‘The effects of magnesium supplementation on exercise performance: A systematic review and meta-analysis’, European Journal of Sport Science, 19(1), pp. 108–117. doi:10.1080/17461391.2018.1481773.

    Hew-Butler, T., Rosner, M.H., Fowkes-Godek, S., Dugas, J.P., Hoffman, M.D., Lewis, D.P., Maughan, R.J., Miller, K.C., Montain, S.J., Rehrer, N.J., Roberts, W.O., Rogers, I.R., Siegel, A.J., Stuempfle, K.J., Winger, J.M. and Verbalis, J.G. (2015) ‘Statement of the Third International Exercise-Associated Hyponatremia Consensus Development Conference, Carlsbad, California, 2015’, Clinical Journal of Sport Medicine, 25(4), pp. 303–320. doi:10.1097/JSM.0000000000000221.

    McCubbin, A.J., Allanson, B.A., Caldwell Odgers, J.N., Cort, M.M., Costa, R.J.S., Cox, G.R., Desbrow, B., Freney, E.G., Gaskell, S.K., Gleeson, M.J., Haslam, R.L., Kelly, V.G., Lis, D.M., Meyer, N.L., Peeling, P. and Slater, G.J. (2019) ‘Sports Dietitians Australia position statement: Nutrition for exercise in hot environments’, International Journal of Sport Nutrition and Exercise Metabolism, 29(5), pp. 549–563. doi:10.1123/ijsnem.2019-0014.

    Maughan, R.J. and Shirreffs, S.M. (2010) ‘Development of hydration strategies to optimize performance for athletes in high-intensity sports and in sports with repeated intense efforts’, Scandinavian Journal of Medicine & Science in Sports, 20(Suppl. 2), pp. 59–69. doi:10.1111/j.1600-0838.2010.01220.x.

    Périard, J.D., Racinais, S. and Sawka, M.N. (2015) ‘Adaptations and mechanisms of human heat acclimation: Applications for competitive athletes and sports’, Scandinavian Journal of Medicine & Science in Sports, 25(Suppl. 1), pp. 20–38. doi:10.1111/sms.12408.

    Sawka, M.N., Burke, L.M., Eichner, E.R., Maughan, R.J., Montain, S.J. and Stachenfeld, N.S. (2007) ‘American College of Sports Medicine position stand: Exercise and fluid replacement’, Medicine & Science in Sports & Exercise, 39(2), pp. 377–390. doi:10.1249/mss.0b013e31802ca597.

    Schwellnus, M.P., Drew, N. and Collins, M. (2011) ‘Muscle cramping in athletes: Clinical assessment, management and prevention’, British Journal of Sports Medicine, 45(4), pp. 247–252. doi:10.1136/bjsm.2010.078535.

    Shirreffs, S.M. and Maughan, R.J. (1998) ‘Volume repletion after exercise-induced volume depletion in humans: Replacement of water and sodium losses’, American Journal of Physiology-Regulatory, Integrative and Comparative Physiology, 274(5), pp. R1480–R1486. doi:10.1152/ajpregu.1998.274.5.R1480.

    Shirreffs, S.M. and Sawka, M.N. (2011) ‘Fluid and electrolyte needs for training, competition and recovery’, Journal of Sports Sciences, 29(Suppl. 1), pp. S39–S46. doi:10.1080/02640414.2011.614269

    World Health Organization (2012) Guideline: Sodium intake for adults and children. Geneva: World Health Organization.  

  • Creatine Supplementation in Male and Female Athletes: An Evidence-Based Review of Mechanisms, Performance, Recovery and Sex-Specific Responses

    Creatine Supplementation in Male and Female Athletes: An Evidence-Based Review of Mechanisms, Performance, Recovery and Sex-Specific Responses

    Introduction

    Creatine monohydrate is one of the most extensively researched and scientifically supported ergogenic aids in sport and exercise science. Contemporary consensus statements confirm that creatine is effective for improving high-intensity exercise performance, increasing lean mass and enhancing training adaptations across a wide range of populations (Kreider et al., 2022; Antonio et al., 2021). Unlike many supplements in sport, creatine has a consistently strong evidence base supported by systematic reviews and meta-analyses, particularly when combined with resistance training (Chilibeck et al., 2017; Candow et al., 2019; Forbes et al., 2021). Although the physiological mechanisms are similar between males and females, emerging evidence suggests sex-specific differences in creatine metabolism, baseline muscle creatine stores and hormonal regulation may influence responsiveness and practical application (Smith-Ryan et al., 2021; Delpino et al., 2022).

    Physiological Role and Mechanisms of Action

    Creatine functions primarily within the phosphagen energy system, supporting rapid ATP regeneration during high-intensity exercise. During maximal effort, ATP is rapidly depleted and resynthesised via phosphocreatine (PCr), catalysed by creatine kinase. Contemporary evidence confirms that creatine supplementation increases intramuscular total creatine and phosphocreatine stores, enhancing ATP resynthesis during repeated high-intensity efforts (Kreider et al., 2022; Forbes et al., 2021). Key physiological effects include increased phosphocreatine availability, enhanced sprint and resistance performance, improved training volume tolerance, intracellular hydration and upregulation of anabolic signalling pathways associated with hypertrophy (Kreider et al., 2022; Antonio et al., 2021). Cell swelling is considered an anabolic stimulus contributing to protein synthesis and reduced protein breakdown (Forbes et al., 2021).

    Creatine and Performance in Males

    Meta-analytical evidence consistently demonstrates creatine improves maximal strength, lean body mass, training volume and muscular hypertrophy when combined with resistance training (Chilibeck et al., 2017; Candow et al., 2019). A meta-analysis reported significantly greater increases in lean mass with creatine supplementation alongside resistance training compared with training alone (Chilibeck et al., 2017). More recent evidence confirms increases in lean body mass of approximately ~1 kg in trained and untrained populations (Delpino et al., 2022). Creatine also improves repeated sprint ability, peak power output and anaerobic performance capacity, making it highly relevant to team sports such as football, rugby and hockey (Kreider et al., 2022; Antonio et al., 2021).

    Creatine and Performance in Females

    Although historically underrepresented in research, recent systematic reviews demonstrate that females benefit from creatine supplementation in strength, high-intensity performance and lean mass adaptations (Smith-Ryan et al., 2021; Delpino et al., 2022). Females typically have lower baseline intramuscular creatine stores and dietary intake, which may influence responsiveness (Smith-Ryan et al., 2021). While absolute gains in lean mass are often smaller than in males, relative improvements are comparable when adjusted for baseline differences (Delpino et al., 2022). Evidence suggests creatine may be particularly relevant in female athletes due to hormonal influences on energy metabolism and creatine kinase activity across the menstrual cycle (Smith-Ryan et al., 2021).

    Creatine and the Menstrual Cycle

    Oestrogen and progesterone fluctuations influence substrate utilisation, neuromuscular performance, thermoregulation and fatigue perception. These hormonal changes may also influence creatine kinase activity and energy metabolism (Smith-Ryan et al., 2021). Although phase-specific intervention studies remain limited, creatine’s role in ATP resynthesis suggests potential benefits during phases of increased fatigue or reduced energy availability.

    Creatine, Recovery and Training Adaptation

    Creatine supplementation may enhance recovery between training sessions and improve tolerance to high training loads. Evidence suggests improvements in training volume capacity, reductions in muscle damage markers in some contexts and enhanced glycogen resynthesis when combined with carbohydrate intake (Antonio et al., 2021; Kreider et al., 2022). These effects are most pronounced when creatine is combined with structured resistance or high-intensity training programmes (Candow et al., 2019).

    Creatine and Cognitive Function

    Creatine plays a role in brain energy metabolism, and supplementation may improve working memory, processing speed and cognitive resilience under stress or sleep deprivation (Antonio et al., 2021; Kreider et al., 2022). These effects are most evident in conditions of metabolic stress, making creatine relevant for athletes experiencing travel, congestion, sleep disruption or high cognitive load. This may also be relevant for female athletes experiencing cyclical fatigue or hormonal fluctuations (Smith-Ryan et al., 2021).

    Creatine Across the Female Lifespan

    In adolescence, creatine supports strength and power development alongside training. During reproductive years, it supports high-intensity performance and recovery. In perimenopause and menopause, creatine combined with resistance training improves lean mass, strength and functional performance (Candow et al., 2019; Delpino et al., 2022). Bone health outcomes remain inconclusive, but functional improvements are consistently reported.

    Safety and Long-Term Use

    Consensus statements confirm creatine monohydrate is safe when used at recommended doses in healthy individuals (Kreider et al., 2022). Evidence does not support adverse effects on kidney function, liver function, hydration status or cramping risk (Antonio et al., 2021; Kreider et al., 2022). Long-term studies support its safety in both male and female populations.

    Practical Application

    Loading phase (optional): 20 g/day split into 4 doses for 5–7 days. Maintenance: 3–5 g/day. Alternatively, 3–5 g/day without loading achieves full saturation over ~3–4 weeks. Timing is not critical; total daily intake is the key factor (Antonio et al., 2021). Creatine monohydrate remains the gold standard due to its efficacy, safety, cost-effectiveness and evidence base (Kreider et al., 2022).

    Conclusion

    Creatine monohydrate is one of the most effective and well-supported supplements in sport science. Evidence demonstrates consistent benefits for strength, lean mass, high-intensity performance, recovery and cognition in both males and females. While males show greater absolute gains in lean mass, this is largely due to baseline physiological differences rather than differences in responsiveness. In females, creatine may have additional relevance due to hormonal fluctuations and lower baseline creatine stores. Overall, creatine should be considered a foundational evidence-based supplement for athletes across sexes and performance levels.

    References

    Antonio, J. et al. (2021) Journal of the International Society of Sports Nutrition, 18, pp.1–17.
    Candow, D.G. et al. (2019) Journal of Clinical Medicine, 8, 488.
    Chilibeck, P.D. et al. (2017) Open Access Journal of Sports Medicine, 8, pp.213–226.
    Delpino, F.M. et al. (2022) Nutrition, 103–104, 111791.
    Forbes, S.C. et al. (2021) Nutrients, 13(6), 1915.
    Kreider, R.B. et al. (2022) Journal of the International Society of Sports Nutrition, 19(1), pp.1–46.
    Smith-Ryan, A.E. et al. (2021) Nutrients, 13(3), 877.

  • Bone Health in Athletes: The Role of Energy Availability, Training Load and Stress Fracture Risk

    Bone Health in Athletes: The Role of Energy Availability, Training Load and Stress Fracture Risk

    Introduction

    Bone is a dynamic tissue that responds continuously to mechanical and metabolic stimuli. In athletic populations, bone health is determined by the interaction between mechanical loading, endocrine function, and energy availability rather than isolated nutrient intake alone (Turner, 1998; Tenforde and Fredericson, 2011).

    Although sports participation is generally associated with higher bone mineral density (BMD), certain training environments particularly those characterised by low energy availability are associated with impaired bone turnover and increased risk of stress injury (Mountjoy et al., 2018; Logue et al., 2020). This makes bone health a critical but often under-monitored determinant of long-term athletic performance and injury resilience.

    Bone Remodelling and Mechanotransduction in Sport

    Bone adapts to mechanical loading via remodelling, a process regulated by osteoblast and osteoclast activity. According to mechanostat theory, bone tissue responds to strain magnitude, rate, and frequency, increasing its structural strength when subjected to sufficient mechanical stress (Turner, 1998).

    High-impact, multidirectional loading sports stimulate osteogenesis more effectively than low-impact endurance activities. Evidence consistently shows higher BMD in athletes participating in sports involving jumping, sprinting, and rapid changes of direction compared with cycling or swimming (Tenforde and Fredericson, 2011).

    However, bone adaptation is not solely dependent on mechanical stimulus. Energy availability and endocrine function significantly modulate the remodelling response, with low energy availability attenuating bone formation despite mechanical loading exposure (Ihle and Loucks, 2004).

    Energy Availability as a Central Regulator of Bone Health

    Energy availability (EA), defined as dietary energy intake minus exercise energy expenditure relative to fat-free mass, is a primary determinant of physiological function in athletes (Loucks et al., 2011).

    Low energy availability impairs bone health through multiple mechanisms including suppression of bone formation markers such as osteocalcin and procollagen type 1 N-terminal propeptide (P1NP), alongside increased bone resorption markers such as C-terminal telopeptide (CTX) (Ihle and Loucks, 2004; Logue et al., 2020).

    Endocrine disruption is also central to this process. Low EA reduces insulin-like growth factor-1 (IGF-1), leptin, oestrogen, and testosterone, all of which are essential regulators of bone metabolism (Mountjoy et al., 2018). These hormonal changes shift bone turnover towards net resorption and impair recovery from microdamage accumulation.

    Stress Fractures and Bone Stress Injuries

    Bone stress injuries represent a continuum from periosteal oedema to cortical fracture and occur when repetitive submaximal loading exceeds the bone’s capacity for remodelling and repair (Warden et al., 2014).

    Key risk factors consistently identified in peer-reviewed literature include low energy availability, rapid increases in training load, prior stress fracture history, hormonal disturbances, and low bone mineral density (Mountjoy et al., 2018; Tenforde et al., 2015).

    Athletes with low energy availability exhibit significantly increased incidence of stress fractures due to impaired bone formation and delayed microdamage repair processes (Logue et al., 2020).

    Hormonal Regulation of Bone Metabolism in Athletes

    Bone remodelling is tightly regulated by endocrine signalling. Oestrogen and testosterone are critical for maintaining bone formation and inhibiting resorption (Mountjoy et al., 2018).

    In low energy availability states, oestrogen concentrations may decrease in female athletes, particularly in cases of functional hypothalamic amenorrhoea, while testosterone may also decline in male athletes. Insulin-like growth factor-1 (IGF-1) is suppressed, reducing osteoblastic activity, while cortisol may increase, promoting catabolic effects on bone tissue (Mountjoy et al., 2018).

    These endocrine changes collectively shift bone metabolism towards increased resorption and reduced formation.

    Mechanical Loading: Protective and Dose-Dependent Effects

    Mechanical loading remains one of the most potent stimuli for bone formation. High-impact loading generates strain-induced deformation and fluid flow within the bone matrix, triggering osteogenic responses (Turner, 1998).

    High-impact sports consistently demonstrate greater bone mineral density compared with low-impact endurance sports (Tenforde and Fredericson, 2011). Furthermore, plyometric and resistance training enhance site-specific bone strength adaptations (Tenforde et al., 2015).

    However, excessive repetitive loading without adequate recovery or energy availability results in microdamage accumulation and increased risk of bone stress injury (Warden et al., 2014).

    Nutrition and Bone Health: Beyond Calcium

    Energy availability is the primary nutritional determinant of bone health in athletes. Low energy availability suppresses bone formation even when calcium and vitamin D intake are adequate (Loucks et al., 2011; Mountjoy et al., 2018).

    Calcium plays a key role in bone mineralisation, but its effectiveness is dependent on hormonal status and energy balance. Vitamin D is essential for calcium absorption and bone metabolism, with deficiency associated with increased fracture risk in athletes (Close et al., 2013).

    Protein intake supports bone matrix formation and collagen synthesis. Evidence indicates that higher protein intakes do not negatively impact bone health when calcium intake is sufficient and may enhance IGF-1-mediated anabolic signalling (Shams-White et al., 2017).

    RED-S and Bone Health

    Relative Energy Deficiency in Sport (RED-S) describes impaired physiological function resulting from low energy availability. Bone health is one of the most significantly affected systems (Mountjoy et al., 2018).

    RED-S is associated with reduced bone formation markers, increased bone resorption, impaired attainment of peak bone mass, and increased stress fracture risk. Persistent low energy availability during key developmental periods may result in long-term deficits in bone mineral density (Mountjoy et al., 2018).

    Integration of Training Load and Energy Availability

    Bone adaptation is dependent on the interaction between mechanical loading and energy availability. Mechanical loading is only osteogenic when sufficient energy is available to support remodelling processes.

    When energy availability is low, the osteogenic response to loading is blunted, bone resorption exceeds formation, and adaptation to training is impaired. This explains the high incidence of bone stress injuries in athletes experiencing high training loads without adequate fuelling (Logue et al., 2020; Warden et al., 2014).

    Practical Implications for Athlete Management

    Optimising bone health in athletes requires a multi-factorial approach that includes maintaining adequate energy availability, structured mechanical loading, and appropriate nutritional support.

    Early identification of RED-S risk factors such as menstrual dysfunction, recurrent stress injury, fatigue, and rapid training load increases is essential for prevention (Mountjoy et al., 2018).

    Conclusion

    Bone health in athletes is governed primarily by the interaction between energy availability, endocrine function, and mechanical loading rather than isolated nutrient intake. Low energy availability is the most significant modifiable risk factor for impaired bone metabolism and stress injury development. Maintaining adequate energy availability alongside structured loading strategies is essential for optimal skeletal adaptation and injury prevention.

    References

    Close, G.L., Leckey, J., Patterson, M., et al. (2013) ‘Vitamin D and skeletal muscle strength in athletes’, Scandinavian Journal of Medicine & Science in Sports.

    Ihle, R. and Loucks, A.B. (2004) ‘Dose-response relationships between energy availability and bone turnover’, Journal of Bone and Mineral Research.

    Logue, D.M., Madigan, S.M., Melin, A., et al. (2020) ‘Low energy availability in athletes’, Sports Medicine.

    Loucks, A.B., Kiens, B. and Wright, H.H. (2011) ‘Energy availability in athletes’, Journal of Sports Sciences.

    Mountjoy, M., Sundgot-Borgen, J., Burke, L., et al. (2018) ‘IOC consensus statement on RED-S’, British Journal of Sports Medicine.

    Shams-White, M.M., Chung, M., et al. (2017) ‘Protein intake and bone health’, American Journal of Clinical Nutrition.

    Tenforde, A.S. and Fredericson, M. (2011) ‘Influence of sports participation on bone health’, Sports Health.

    Tenforde, A.S., et al. (2015) ‘Impact activity and bone density’, PM&R.

    Turner, C.H. (1998) ‘Three rules for bone adaptation’, Bone.

    Warden, S.J., Davis, I.S. and Fredericson, M. (2014) ‘Stress fracture biomechanics’, British Journal of Sports Medicine

  • Continuous Glucose Monitoring in Healthy Individuals: Evidence, Interpretation, and Practical Value Beyond Clinical Use

    Continuous Glucose Monitoring in Healthy Individuals: Evidence, Interpretation, and Practical Value Beyond Clinical Use

    Introduction

    Continuous glucose monitoring (CGM) systems are well established in diabetes care, where strong evidence demonstrates improvements in glycaemic variability, time in range, and hypoglycaemia prevention in both type 1 and insulin-treated type 2 diabetes populations (Battelino et al., 2019; Beck et al., 2017). In recent years, CGMs have increasingly been adopted by individuals without diabetes for purposes such as dietary optimisation, metabolic health tracking, and performance monitoring. This expansion reflects interest in precision nutrition, although evidence supporting clinical benefit in healthy populations remains limited (Liao et al., 2026). The key question is whether additional metabolic data improves outcomes in already well-regulated physiology.

    Physiological Basis of CGM Technology

    CGMs measure glucose in interstitial fluid using enzymatic sensors. Interstitial glucose is physiologically linked to blood glucose but is not identical. A consistent limitation is the time lag between blood and interstitial compartments, typically 5–15 minutes depending on metabolic state and perfusion (Torimoto and Okada, 2021). This lag becomes more pronounced during rapid changes such as postprandial absorption or exercise. Accuracy is also influenced by sensor kinetics, calibration algorithms, and tissue-level variability. Facchinetti (2016) notes that CGM accuracy is generally acceptable in diabetic ranges but is reduced at lower glucose levels and during rapid glycaemic shifts, which are more typical in healthy individuals. This means CGM outputs in normoglycaemic populations should be interpreted as trend-based estimates rather than precise biochemical measurements.

    Inter-Individual Variability in Glycaemic Response

    A key rationale for CGM use in personalised nutrition is inter-individual variability in postprandial glycaemic responses (PPGRs). Zeevi et al. (2015) demonstrated that identical meals produce highly variable glucose responses driven by factors including microbiome composition, insulin sensitivity, sleep, and anthropometrics. Their machine-learning model was able to predict PPGRs and showed that personalised dietary interventions could reduce postprandial glucose excursions. Mendes-Soares et al. (2019) replicated these findings in an independent cohort, confirming that glycaemic responses are highly individualised. Mechanistically, variability reflects differences in gastric emptying, insulin secretion dynamics, hepatic glucose output, and peripheral glucose uptake. However, variability in physiological response does not necessarily imply that reducing all glucose excursions improves long-term health outcomes.

    CGM Effects in Non-Diabetic Populations

    The most comprehensive synthesis of evidence is provided by Liao et al. (2026), who conducted a systematic review and meta-analysis of CGM use in non-diabetic populations. They reported small reductions in mean glucose and improved dietary awareness, but no consistent improvements in BMI, glycaemic variability, or long-term metabolic outcomes in healthy individuals. Benefits were more evident in individuals with impaired glucose regulation, suggesting CGM utility may be dependent on baseline metabolic status. These findings indicate CGMs function more effectively as behavioural feedback tools than as metabolic intervention devices in healthy populations.

    Do Postprandial Glucose Spikes Matter?

    Postprandial increases in glucose are a normal physiological response to carbohydrate ingestion. In healthy individuals, glucose homeostasis is maintained through coordinated insulin secretion, hepatic regulation, and peripheral uptake. DeFronzo et al. (2015) describe these responses as central to metabolic flexibility rather than pathological dysfunction. While glycaemic variability has been associated with adverse outcomes in diabetic populations, causality in healthy individuals is not established. No randomised controlled trials demonstrate that reducing physiological glucose excursions improves cardiovascular outcomes, body composition, or longevity in normoglycaemic populations.

    CGM Accuracy and Interpretation Limitations

    CGM interpretation is limited by both physiological and technical factors. Interstitial lag introduces temporal discrepancy between blood and tissue glucose (Torimoto and Okada, 2021). Sensor accuracy decreases during rapid glucose fluctuations and at lower glucose ranges (Facchinetti, 2016). In healthy individuals, where glucose variability is relatively small, these limitations may disproportionately influence interpretation, increasing the risk of misclassifying normal physiological variation as meaningful metabolic disturbance.

    Behavioural and Psychological Considerations

    CGMs provide continuous physiological feedback, which can influence behaviour. Vettoretti et al. (2020) highlight that while CGMs may improve awareness of dietary patterns, continuous monitoring can also increase cognitive load and attention bias toward short-term fluctuations. This may lead to over-interpretation of normal glucose variability, increased dietary restriction, and reduced dietary flexibility in some individuals. Importantly, there is no evidence that focusing on minimising all glucose excursions improves dietary quality or long-term health outcomes in healthy populations.

    CGMs in Sport and Exercise

    CGMs are increasingly used in athletic populations to monitor carbohydrate availability, fuelling strategies, and recovery nutrition. However, exercise significantly alters glucose kinetics through catecholamine-mediated hepatic glucose output, increased skeletal muscle uptake, and changes in insulin sensitivity. These physiological responses complicate interpretation of CGM data during training and recovery. Jeukendrup (2017) notes that while carbohydrate availability is central to performance, there is no strong evidence that CGM-guided nutrition improves athletic performance outcomes in controlled trials.

    Future Directions: Precision Nutrition

    CGMs are being integrated into precision nutrition models alongside microbiome and dietary data. Zeevi et al. (2015) and Mendes-Soares et al. (2019) demonstrated that machine-learning approaches can predict individual glycaemic responses with moderate accuracy, supporting the concept of metabolic phenotyping. However, translation into clinical practice remains limited due to lack of long-term outcome data, limited external validity, and absence of large-scale randomised controlled trials demonstrating clinical benefit.

    Practical Implications

    Current evidence suggests CGMs may improve short-term dietary awareness and engagement behaviours (Liao et al., 2026). Individual variability in glycaemic response is well established (Zeevi et al., 2015), but does not justify routine intervention in healthy populations. Physiological glucose excursions are not inherently harmful (DeFronzo et al., 2015). CGM data must be interpreted cautiously due to physiological lag and measurement limitations (Facchinetti, 2016). Behavioural effects may be beneficial or maladaptive depending on the individual context (Vettoretti et al., 2020).

    Are CGMs Worth Using in Healthy Individuals?

    In healthy individuals, CGMs are not currently supported as a routine metabolic optimisation tool. Evidence suggests their primary value is educational and behavioural rather than clinical. They may help increase awareness of dietary patterns and individual variability but do not currently demonstrate improvements in body composition, performance, or long-term health outcomes (Liao et al., 2026). In individuals with impaired glucose regulation, CGMs may have greater utility as part of lifestyle intervention strategies. In athletes, CGMs may provide descriptive insights into fuelling responses but lack evidence for performance enhancement. Overall, CGMs should be considered informational rather than interventional tools in healthy populations.

    Conclusion

    Continuous glucose monitoring is a well-established clinical tool in diabetes management and an emerging technology in personalised nutrition. However, current evidence does not support routine use in healthy individuals for improving metabolic health, performance, or body composition. While CGMs provide valuable insight into inter-individual variability in glycaemic responses, physiological glucose excursions in healthy individuals are not inherently pathological, and the clinical significance of modifying them remains unproven. CGMs are best viewed as research and educational tools rather than essential health optimisation devices in normoglycaemic populations.

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    References

    Battelino, T., Danne, T., Bergenstal, R.M., Amiel, S.A., Beck, R., Biester, T., et al. (2019) ‘Clinical targets for continuous glucose monitoring data interpretation: recommendations from the international consensus on time in range’, Diabetes Care, 42(8), pp. 1593–1603.

    Beck, R.W., Riddlesworth, T.D., Ruedy, K., Ahmann, A., Bergenstal, R., Haller, S. (2017) ‘Effect of continuous glucose monitoring on glycemic control in adults with type 1 diabetes using insulin injections’, Annals of Internal Medicine, 167(6), pp. 365–374.

    DeFronzo, R.A., Ferrannini, E., Groop, L., Henry, R.R., Herman, W.H., Holst, J.J., et al. (2015) ‘Type 2 diabetes mellitus’, Diabetes Care, 38(1), pp. 142–150.

    Facchinetti, A. (2016) ‘Continuous glucose monitoring sensors: past, present and future algorithmic challenges’, Sensors, 16(12), 2098.

    Jeukendrup, A.E. (2017) ‘Periodized nutrition for athletes’, Sports Medicine, 47(S1), pp. 51–63.

    Liao, X., et al. (2026) ‘Continuous glucose monitoring in non-diabetic individuals: systematic review and meta-analysis’, European Journal of Medical Research, 31, pp. 1–15.

    Mendes-Soares, H., et al. (2019) ‘Assessment of a personalized approach to predicting postprandial glycemic responses’, Cell Host & Microbe, 26(3), pp. 424–435.

    Torimoto, K. and Okada, Y. (2021) ‘Accuracy and limitations of continuous glucose monitoring systems’, Diabetology International, 12, pp. 1–10.

    Vettoretti, M., Facchinetti, A. and Sparacino, G. (2020) ‘Continuous glucose monitoring: interpretation and behavioural implications’, Diabetes Technology & Therapeutics, 22(9), pp. 1–10.

    Zeevi, D., Korem, T., Zmora, N., Israeli, D., Rothschild, D., Weinberger, A., et al. (2015) ‘Personalized nutrition by prediction of glycemic responses’, Cell, 163(5), pp. 1079–1094

  • Sleep Optimisation for Athletes: A Critical Evidence-Based Review of Recovery, Behaviour and Performance

    Sleep Optimisation for Athletes: A Critical Evidence-Based Review of Recovery, Behaviour and Performance

    Introduction

    Sleep is widely recognised as a foundational biological process underpinning recovery, cognitive performance and physiological adaptation. In athletic populations, sleep is increasingly considered a modifiable performance variable alongside training load and nutrition. A consensus statement on sleep and the athlete reports that many athletes fail to achieve recommended sleep durations, particularly during periods of travel, competition and intensified training (Walsh et al., 2021). This article critically evaluates peer-reviewed evidence on sleep and athletic performance, with emphasis on physiological mechanisms, behavioural constraints and applied strategies relevant to coaches and athletes.

    Sleep Physiology and Performance-Relevant Functions

    Sleep consists of non-rapid eye movement (NREM) and rapid eye movement (REM) stages, both contributing to recovery and adaptation. Evidence indicates NREM sleep is associated with tissue repair, immune regulation and growth hormone secretion (Dattilo et al., 2011; Halson, 2014) while REM sleep is associated with memory consolidation and motor learning (Walker and Stickgold, 2006; Rasch and Born, 2013). Sleep is therefore involved in neuromuscular adaptation, cognitive processing and recovery from training load (Fullagar et al., 2015; Halson, 2014).

    Consequences of Sleep Restriction

    Sleep restriction has been associated with:

    • Impaired cognitive performance and reaction time (Lim and Dinges, 2010; Pilcher and Huffcutt, 1996)
    • Reduced endurance performance and increased perceived exertion (Fullagar et al., 2015; Halson, 2014)
    • Reduced sprint and sport-specific performance (Mah et al., 2011; Waterhouse et al., 2007)
    • Increased injury risk in youth athletes (Milewski et al., 2014; Watson, 2017)
    • Impaired glucose regulation and insulin sensitivity (Spiegel et al., 1999; Tasali et al., 2008)
    • Altered appetite regulation and increased energy intake (Taheri et al., 2004; St-Onge et al., 2016)

    Why Athletes Experience Sleep Disruption

    Evening training, elevated sympathetic activity, increased core temperature and travel all contribute to disrupted sleep patterns (Fullagar et al., 2015; Samuels, 2012).

    Lifestyle Behaviours and Sleep

    Video gaming, social media use, streaming and bedtime procrastination are all associated with delayed sleep onset and reduced sleep duration (Weaver et al., 2010; Levenson et al., 2017; Exelmans and Van den Bulck, 2016).

    Caffeine and Alcohol

    Caffeine reduces sleep duration and quality even when consumed up to 6 hours pre-bed (Drake et al., 2013). Alcohol disrupts REM sleep and increases nocturnal awakenings (Ebrahim et al., 2013).

    Sleep Extension and Napping

    Sleep extension improves sprint performance and reaction time in athletes (Mah et al., 2011). Short naps improve alertness and cognitive performance (Waterhouse et al., 2007).

    Sleep Hygiene

    Consistent routines and reduced evening stimulation improve subjective sleep quality but show variable objective effects (Irish et al., 2015).

    Nutritional Interventions and Sleep

    Nutrition may influence sleep via neurotransmitter synthesis, thermoregulation, glucose metabolism and circadian signalling, although the evidence base remains heterogeneous.

    Carbohydrate Timing and Glycaemic Response

    High glycaemic carbohydrate intake may reduce sleep onset latency via insulin-mediated amino acid shifts increasing tryptophan availability (Afaghi et al., 2007). However, systematic reviews highlight inconsistent findings and strong dependence on timing, dose and individual variability (St-Onge et al., 2016). In practice, carbohydrate intake should prioritise performance recovery rather than sleep manipulation.

    Protein Intake and Pre-Sleep Nutrition

    Pre-sleep protein ingestion does not impair sleep architecture and may support overnight muscle protein synthesis (Res et al., 2012; Trommelen and van Loon, 2016). However, there is no evidence that protein directly improves sleep quality, reinforcing its role in recovery rather than sleep optimisation.

    Tart Cherry Juice

    Tart cherry supplementation may improve sleep duration and efficiency, potentially via melatonin content and anti-inflammatory effects (Howatson et al., 2012; Pigeon et al., 2010). Evidence remains limited by small sample sizes and short trial durations.

    Glycine Supplementation

    Glycine may improve subjective sleep quality and reduce fatigue via thermoregulatory and inhibitory neurotransmission pathways (Inagawa et al., 2006; Bannai and Kawai, 2012). However, replication in athletic populations is lacking.

    Magnesium

    Magnesium influences neuromuscular excitability and stress regulation relevant to sleep physiology (Boyle et al., 2017). A randomised controlled trial showed improved sleep quality in older adults with insomnia symptoms (Abbasi et al., 2012). However, systematic reviews highlight limited and inconsistent evidence, with poor generalisability to young athletic populations (Boyle et al., 2017). Magnesium should therefore be targeted primarily at individuals with low dietary intake rather than used universally.

    Melatonin

    Melatonin is effective for circadian disruption such as jet lag but shows inconsistent benefits in healthy non-shifted populations (Herxheimer and Petrie, 2002; Ferracioli-Oda et al., 2013).

    Caffeine–Sleep Interaction

    Caffeine significantly impairs sleep duration and quality even when consumed 6 hours before bedtime (Drake et al., 2013; Clark and Landolt, 2017).

    Wearable Sleep Tracking

    Wearable devices are widely used in sport for sleep monitoring but show only moderate accuracy for total sleep time and poor accuracy for sleep staging compared with polysomnography (de Zambotti et al., 2018; Chinoy et al., 2021). Their primary value lies in tracking behavioural metrics such as sleep opportunity, bedtime consistency and wake timing rather than physiological sleep architecture. Athletic populations may experience further inaccuracies due to elevated heart rate and training stress. Psychological effects such as orthosomnia may also influence sleep perception. Wearables should therefore be used as behavioural monitoring tools rather than diagnostic instruments.

    Practical Recommendations (Evidence-Graded)

    Strong Evidence

    • Aim for 8–10 hours sleep opportunity per night (Walsh et al., 2021)
    • Avoid caffeine within 6 hours of sleep (Drake et al., 2013)
    • Avoid alcohol before bedtime (Ebrahim et al., 2013)
    • Maintain consistent sleep–wake schedules (Irish et al., 2015)

    Moderate Evidence

    • Sleep extension during heavy training (Mah et al., 2011)
    • Short naps (~20–30 min) for performance and alertness (Waterhouse et al., 2007)
    • Sleep hygiene strategies (Irish et al., 2015)
    • Reduce evening digital stimulation (Levenson et al., 2017)

    Emerging Evidence

    • Tart cherry supplementation (Howatson et al., 2012)
    • Glycine supplementation (Inagawa et al., 2006)
    • Melatonin for jet lag/circadian disruption (Ferracioli-Oda et al., 2013)

    Conclusion

    Sleep is a key recovery modulator in athletic performance, with strong evidence linking restriction to impaired cognitive, metabolic and physical outcomes. However, sleep is influenced by behavioural, nutritional and environmental factors including caffeine, alcohol, digital media use and training schedules. The strongest interventions remain behavioural: increasing sleep opportunity, reducing evening stimulation and maintaining consistent routines. Nutritional and technological interventions may offer adjunct support but remain secondary to foundational sleep behaviours.

    REFERENCES

    Abbasi, B. et al. (2012) ‘The effect of magnesium supplementation on primary insomnia in elderly: A double-blind placebo-controlled clinical trial’, Journal of Research in Medical Sciences.


    Afaghi, A. et al. (2007) ‘High-glycemic-index carbohydrate meals and sleep onset’, American Journal of Clinical Nutrition.


    Bannai, M. and Kawai, N. (2012) ‘New therapeutic strategy for amino acids in sleep’, Journal of Pharmacological Sciences.


    Boyle, N.B. et al. (2017) ‘The effects of magnesium supplementation on subjective anxiety and stress’, Nutrients.


    Clark, I. and Landolt, H. (2017) ‘Coffee, caffeine, and sleep’, Journal of Sleep Research.


    Dattilo, M. et al. (2011) ‘Sleep and muscle recovery’, Sports Medicine.


    de Zambotti, M. et al. (2018) ‘Wearable sleep technology accuracy’, Journal of Clinical Sleep Medicine.


    Drake, C. et al. (2013) ‘Caffeine effects on sleep’, Journal of Clinical Sleep Medicine.


    Ebrahim, I.O. et al. (2013) ‘Alcohol and sleep architecture’, Alcoholism: Clinical and Experimental Research.


    Exelmans, L. and Van den Bulck, J. (2016) ‘Bedtime procrastination’, Journal of Sleep Research.


    Ferracioli-Oda, E. et al. (2013) ‘Melatonin and sleep outcomes’, PLoS One.


    Fullagar, H.H.K. et al. (2015) ‘Sleep and athletic performance’, Sports Medicine.


    Halson, S.L. (2014) ‘Sleep in elite athletes’, Sports Medicine.


    Herxheimer, A. and Petrie, K.J. (2002) ‘Melatonin for jet lag’, Cochrane Database.


    Howatson, G. et al. (2012) ‘Tart cherry juice and recovery’, Scandinavian Journal of Medicine & Science in Sports.


    Inagawa, K. et al. (2006) ‘Glycine and sleep quality’, Journal of Pharmacological Sciences.


    Irish, L.A. et al. (2015) ‘Sleep hygiene review’, Sleep Medicine Reviews.


    King, D.L. et al. (2013) ‘Gaming and sleep’, Journal of Clinical Sleep Medicine.


    Kredlow, M.A. et al. (2015) ‘Sleep hygiene effectiveness’, Journal of Behavioral Medicine.


    Levenson, J.C. et al. (2017) ‘Social media use and sleep’, Preventive Medicine.


    Lim, J. and Dinges, D.F. (2010) ‘Sleep deprivation and cognition’, Psychological Bulletin.


    Mah, C.D. et al. (2011) ‘Sleep extension in athletes’, Sleep.


    Milewski, M.D. et al. (2014) ‘Sleep and injury risk’, Journal of Pediatric Orthopaedics.


    Pigeon, W.R. et al. (2010) ‘Tart cherry and sleep’, Journal of Medicinal Food.


    Rasch, B. and Born, J. (2013) ‘Sleep and memory’, Physiological Reviews.


    Res, P. et al. (2012) ‘Pre-sleep protein intake’, Medicine & Science in Sports & Exercise.


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    Samuels, C. (2012) ‘Jet lag in athletes’, Sports Medicine.


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  • Peptides in the Fitness Industry: Mechanisms, Adaptation, Evidence, Risks and Scientific Limitations.

    Peptides in the Fitness Industry: Mechanisms, Adaptation, Evidence, Risks and Scientific Limitations.

    Peptides have moved rapidly from biomedical research into mainstream fitness culture, marketed as a targeted means of enhancing muscle growth, recovery and overall physiological function. They are often presented as a “precision” alternative to traditional performance-enhancing approaches, promising specific, controllable effects with fewer risks. However, a closer examination of the scientific literature reveals a more complex and far less certain picture. While peptide biology is well understood at a mechanistic level, the evidence supporting meaningful improvements in training adaptation and athletic performance is limited, inconsistent and frequently constrained by methodological weaknesses. The key issue is therefore not whether peptides can influence physiology, but whether they meaningfully improve adaptation to training, which remains the primary determinant of performance outcomes.

    What Are Peptides

    Peptides are short chains of amino acids that function predominantly as signalling molecules within the body. Unlike larger proteins, which primarily serve structural or enzymatic roles, peptides regulate biological processes by binding to receptors and initiating intracellular responses. A number of critical physiological regulators are peptides, including insulin and insulin-like growth factor‑1, which plays a central role in skeletal muscle growth, regeneration and adaptation through its influence on satellite cell activity and protein synthesis pathways (Ahmad et al., 2020). In applied fitness settings, peptides typically refer to synthetic analogues designed to manipulate these signalling systems, often through hormonal or regenerative pathways.

    Mechanisms of Action

    The Growth Hormone–IGF‑1 Axis

    The most extensively discussed mechanism underpinning peptide use in fitness is the growth hormone–IGF‑1 axis. Growth hormone is secreted from the pituitary gland and stimulates the production of IGF‑1 both systemically and within muscle tissue. IGF‑1 then binds to receptors on muscle cells, activating intracellular pathways such as PI3K/Akt and mTOR, which regulate protein synthesis, cell proliferation and survival (Machida and Booth, 2004; Ahmad et al., 2020). Through these mechanisms, IGF‑1 facilitates satellite cell activation, muscle fibre hypertrophy and tissue repair following damage.

    Interaction With Exercise Physiology

    Resistance exercise itself strongly activates the same pathways targeted by peptides. Mechanical loading increases local IGF‑1 expression within muscle tissue and stimulates mTOR signalling, which is central to muscle protein synthesis (Machida and Booth, 2004). This highlights an important limitation: peptides are not introducing new biological mechanisms but attempting to manipulate systems already maximally stimulated through appropriate training and nutrition.

    Tissue Repair and Regeneration Pathways

    Some peptides are proposed to influence recovery through mechanisms such as angiogenesis, enhanced collagen synthesis, modulation of inflammatory pathways and improved fibroblast activity. These mechanisms underpin claims relating to improved healing of connective tissues and reduced injury recovery time. However, the evidence supporting these claims is heavily dominated by preclinical animal research, with limited high-quality human validation.

    Training Adaptation: The Central Issue

    Training adaptation is a multifactorial process driven by the interaction between mechanical, metabolic and biological signals. It depends on progressive overload, motor unit recruitment, neuromuscular adaptation, nutrient availability and recovery processes rather than a single signalling pathway. Peptides influence only a narrow component of this system, primarily intracellular signalling.

    Adaptation follows a sequence whereby a sufficient training stimulus produces intracellular signalling, leading to protein synthesis, structural change and ultimately functional improvement. Peptides act at the signalling stage but do not replace the initial mechanical stimulus. This leads to a critical principle: increasing signalling alone does not produce meaningful adaptation in the absence of appropriate training.

    A consistent finding across the literature is the discrepancy between molecular responses and functional outcomes. Studies often demonstrate increases in IGF‑1, activation of anabolic signalling pathways and changes in gene expression, yet these do not consistently translate into increased strength, improved power output or enhanced performance. For example, collagen peptide studies show increased signalling pathway activation without significant improvements in strength or functional performance (Centner et al., 2022; Balshaw et al., 2022). This highlights that molecular changes are necessary but not sufficient for meaningful adaptation.

    Adaptation is also constrained by limiting factors such as training stimulus, protein intake, energy availability and recovery. Peptides do not override these constraints, meaning increased signalling cannot compensate for inadequate training or nutrition. Additionally, most peptide studies are conducted in untrained or clinical populations, where adaptive capacity is higher. In trained athletes, physiological systems are already optimised, meaning the marginal benefit of additional signalling is likely to be minimal due to ceiling effects.

    Evidence Base

    Growth Hormone and Related Interventions

    The strongest human evidence comes from research on growth hormone. Randomised controlled trials demonstrate that growth hormone administration can increase lean body mass and reduce fat mass, particularly in ageing or hormone-deficient populations (Hoffman et al., 2004; Fernández‑Garza et al., 2025). However, interpretation of these findings is complex. Growth hormone increases extracellular fluid retention and connective tissue mass, meaning increases in lean mass do not necessarily represent increases in contractile muscle tissue.

    Despite changes in body composition, functional outcomes are inconsistent. Upper-body strength often shows no significant improvement, while lower-body strength gains are modest and variable (Tavares et al., 2013). Performance outcomes are rarely improved, indicating that growth hormone-related hypertrophy is not equivalent to training-induced hypertrophy.

    Growth hormone interventions are also associated with metabolic consequences, including reduced insulin sensitivity and impaired glucose tolerance (Fernández‑Garza et al., 2025). These findings raise concerns regarding long-term health risks and highlight the importance of risk–benefit analysis.

    Collagen Peptides and Resistance Training

    Research on collagen peptides provides additional insight into the disconnect between molecular signalling and functional outcomes. Acute studies demonstrate increased activation of anabolic signalling pathways following collagen supplementation and resistance exercise (Centner et al., 2022). However, longer-term studies show increases in muscle volume without corresponding improvements in strength or performance (Balshaw et al., 2022). This suggests that structural changes at the tissue level do not necessarily translate into functional improvements.

    Protein Versus Peptides

    Comparative studies consistently demonstrate that protein quality and quantity are more important determinants of adaptation than peptide supplementation. Whey protein has been shown to produce greater increases in muscle size than collagen peptides, despite matched leucine content, while strength gains remain similar (Jacinto et al., 2022). This reinforces established principles of sports nutrition, where total protein intake and amino acid availability drive adaptation.

    Recovery Peptides

    Recovery peptides such as BPC‑157 are widely discussed within fitness circles but lack robust human evidence. Systematic reviews indicate that the majority of studies are preclinical, with very few human trials and a lack of randomised controlled evidence (Vasireddi et al., 2025). Narrative reviews further confirm that although animal models demonstrate promising effects, these findings have not been reliably replicated in humans (McGuire et al., 2025). Current claims regarding recovery peptides are therefore not supported by strong clinical data.

    Study Design Limitations

    The peptide evidence base is limited by consistent methodological issues. Many studies involve small sample sizes, reducing statistical power and increasing variability. Research is often conducted in non-athletic populations, limiting applicability to trained individuals. Study durations are typically short, preventing long-term conclusions about adaptation or safety.

    There is a heavy reliance on surrogate outcomes such as lean body mass, hormone concentrations and gene expression, which do not necessarily reflect real-world performance outcomes. Confounding variables such as training programme design, nutritional intake and recovery practices are often not well controlled. Additionally, there is a lack of replication across independent studies and a significant translational gap between animal and human research, particularly in recovery peptide investigations.

    Safety Considerations

    Acute risks include fluid retention, impaired glucose metabolism, reduced insulin sensitivity and injection-related complications. Chronic risks are less well understood but potentially more serious. IGF‑1 promotes cell proliferation and inhibits apoptosis, and chronic elevation is associated with increased cancer risk (Ahmad et al., 2020). Long-term concerns also include cardiovascular strain, endocrine disruption and metabolic dysfunction. A key limitation is the absence of long-term human safety data, meaning the true risk profile remains unclear.

    Practical Implications

    Peptides should not be considered first-line interventions for performance enhancement. Training, nutrition and recovery remain the primary drivers of adaptation. Peptides should be viewed as experimental due to the limited and inconsistent evidence base. The risk–reward profile is currently unfavourable, with modest potential benefits and uncertain long-term risks.

    Practitioners should prioritise evidence-based strategies and educate athletes on the limitations of current knowledge. Any consideration of peptide use should occur within a medically supervised context. Focus should remain on progressive resistance training, adequate protein intake, creatine supplementation and sleep optimisation, all of which are supported by high-quality evidence.

    Final Conclusion

    Peptides are biologically plausible and mechanistically sound, influencing key pathways involved in muscle growth and recovery. However, the current evidence indicates that they do not meaningfully enhance training adaptation or performance beyond what can be achieved through well-structured training and nutrition.

    The literature is constrained by methodological weaknesses, non-athletic populations, reliance on surrogate outcomes and limited long-term data. At the same time, safety concerns remain unresolved.

    From a performance perspective, peptides do not replace training, do not reliably enhance adaptation and should currently be regarded as experimental rather than evidence-based tools. The fundamentals of performance continue to provide the most effective and reliable outcomes.

    References

    Ahmad, S.S. et al. (2020) Implications of insulin-like growth factor‑1 in skeletal muscle and various diseases. Cells, 9(8), 1773

    Balshaw, T.G. et al. (2022) The effect of specific bioactive collagen peptides on function and muscle remodeling during human resistance training. Acta Physiologica

    Centner, C. et al. (2022) Supplementation of specific collagen peptides following high-load resistance exercise upregulates gene expression. Frontiers in Physiology

    Fernández‑Garza, L.E. et al. (2025) Growth hormone and aging: a clinical review. Frontiers in Aging

    Hoffman, A.R. et al. (2004) Growth hormone replacement therapy in adult-onset GH deficiency. Journal of Clinical Endocrinology & Metabolism

    Jacinto, J.L. et al. (2022) Whey protein supplementation is superior to leucine-matched collagen peptides. International Journal of Sport Nutrition and Exercise Metabolism

    Machida, S. and Booth, F.W. (2004) Insulin-like growth factor‑1 and satellite cell proliferation. Proceedings of the Nutrition Society

    McGuire, F.P. et al. (2025) Regeneration or risk? A narrative review of BPC‑157. Current Reviews in Musculoskeletal Medicine

    Tavares, A.B. et al. (2013) Effects of growth hormone administration on muscle strength. International Journal of Endocrinology

    Vasireddi, S. et al. (2025) Systematic review of BPC‑157 for orthopaedic applications. American Journal of Sports Medicine

  • Under-Fuelling in Football: The Hidden Performance Constraint Across All Levels of the Game

    In modern football, training loads, match intensity, and fixture congestion have increased significantly across all levels of the game. Yet despite these rising demands, research consistently shows that many footballers are still not consuming enough energy to fully support performance, recovery, and adaptation.

    This mismatch between energy intake and energy expenditure is known as low energy availability (LEA) and is a key component of Relative Energy Deficiency in Sport (RED-S). The IOC consensus statement defines RED-S as a syndrome caused by insufficient energy intake relative to exercise energy expenditure, leading to impaired physiological function, health, and performance (Mountjoy et al., 2023).

    Under-Fuelling in Football: The Core Issue

    Under-fuelling occurs when a footballer consistently fails to meet the energy demands of training, match play, and recovery.

    This includes:

    • Training sessions across the week
    • Match play (high-intensity intermittent activity)
    • Gym and strength work
    • Recovery processes such as glycogen restoration and tissue repair

    In practice, under-fuelling is rarely intentional. It is usually driven by poor planning, appetite suppression post-training, time constraints, or misinformed body composition strategies.

    Over time, even small energy deficits accumulate and act as a chronic performance constraint, limiting adaptation and consistency across a season.

    How Common is Under-Fuelling in Football

    Professional male footballers

    Even at elite level, research shows that under-fuelling persists.

    A doubly labelled water study in professional male footballers reported:

    • Energy expenditure: ~3,170 kcal/day
    • Energy intake: ~2,620 kcal/day
    • Result: consistent energy deficit across training weeks

    Despite access to full-time performance support, players still failed to consistently match intake to expenditure, highlighting poor nutritional periodisation in elite environments (Collins et al., 2025).

    This mismatch becomes more pronounced during congested fixture periods, where intake fails to scale with increased load.

    Female footballers

    Research in elite female footballers shows frequent periods of low energy availability during training blocks.

    Findings include:

    • Energy intake often below expenditure
    • Carbohydrate intake below performance recommendations
    • Increased risk of low energy availability during congested training phases (Smavik Dasa et al., 2022)

    These conditions increase risk of RED-S and impair recovery and performance consistency (Mountjoy et al., 2023).

    Male academy and youth footballers

    Emerging evidence suggests low energy availability is also present in male academy footballers aged 16–23 years.

    Key issues include:

    • Energy intake not matching training and growth demands
    • Inadequate carbohydrate availability around training
    • Increased vulnerability during puberty and late adolescence (Purcell, 2013; Tenforde et al., 2021)

    At this stage, athletes are balancing performance demands with growth and development, increasing overall energy requirements.

    Why Footballers Are at High Risk

    Football presents a unique metabolic environment due to:

    • Matches costing 1,000–1,500+ kcal
    • 4–10 training sessions per week
    • Rapid glycogen depletion from repeated sprint activity
    • Appetite suppression after high-intensity training
    • Limited time for structured eating
    • Body composition pressures even at elite level

    The result is a sport where energy demand is consistently high, but intake often fails to keep pace.

    What Happens in the Body When a Footballer Under-Fuels

    When energy intake is consistently too low, the body enters a state of energy conservation, downregulating non-essential physiological processes such as reproduction, adaptation, and recovery in order to maintain essential functions and overall homeostasis (Areta & Taylor, 2021; Guisado-Cuadrado et al., 2026).

    This is not a simple “survival mode switch”, but a coordinated physiological response across multiple systems.

    Metabolic system

    • Reduced resting metabolic rate
    • Reduced capacity for high-intensity output

    Endocrine system

    • Reduced testosterone availability
    • Altered thyroid function
    • Increased cortisol response

    Musculoskeletal system

    • Reduced muscle protein synthesis
    • Impaired adaptation to training

    Bone health

    • Reduced bone turnover
    • Increased injury risk over time

    Immune function

    • Increased illness risk during heavy training blocks (Mountjoy et al., 2023)

    Performance Consequences in Football

    Under-fuelling acts as a hidden performance constraint, reducing output even when training load is maintained.

    Key effects include:

    • Reduced high-intensity running output
    • Lower repeated sprint ability
    • Reduced technical and cognitive performance late in matches
    • Increased perceived exertion
    • Slower recovery between fixtures

    Athletes may maintain workload but fail to adapt positively when energy availability is insufficient (Burke et al., 2021).

    Signs a Footballer May Be Under-Fuelled

    Performance signs

    • Drop in sprint speed or power
    • Reduced high-intensity output in matches

    Physiological signs

    • Persistent fatigue
    • Frequent soft tissue injuries
    • Poor recovery between sessions

    Body composition signs

    • Unintentional weight loss
    • Loss of lean mass over time

    Behavioural signs

    • Skipping meals or recovery nutrition
    • Low appetite post-training
    • Inconsistent eating patterns

    In youth players, reduced development or stalled progression may also be present (Purcell, 2013).

    Why Professional Male Footballers Are Still at Risk

    Even in elite environments with full support staff, professional male footballers still show:

    • Chronic mismatch between intake and expenditure
    • Poor day-to-day nutritional periodisation
    • Failure to scale intake to match or recovery days (Collins et al., 2025)

    This highlights that under-fuelling is not just a knowledge issue, but a system-level performance constraint influenced by scheduling, behaviour, and environment.

    How to Reduce the Risk of Under-Fuelling

    1. Fuel around training

    Prioritise carbohydrate intake before and after training sessions.

    2. Periodise energy intake

    Increase intake on:

    • Match days
    • Double training days
    • High-load microcycles

    3. Use structured snacks

    Easy additions that increase total intake:

    • Sandwiches
    • Yoghurts and fruit
    • Smoothies
    • Cereal with milk

    4. Prioritise recovery nutrition

    Refuel within 1–2 hours post-exercise to support glycogen restoration and adaptation.

    5. Monitor unintended weight loss

    Consistent weight loss across a season may indicate chronic under-fuelling.

    6. Reframe performance messaging

    “Eat less to stay lean” becomes “fuel to train hard, recover, and stay available for selection.”

    Key Takeaway

    Under-fuelling is one of the most overlooked performance constraints in football.

    Across professional male footballers, female players, and academy environments, research consistently shows that energy intake often fails to meet the demands of training and competition.

    This leads to reduced adaptation, impaired performance, and increased injury risk across the season.

    In football:

    You do not adapt to training you cannot recover from.

    Energy availability is not just nutrition it is a core determinant of performance capacity.

    Put Nutrition Periodisation into Practice

    Understanding the principles of nutrition periodisation is one thing—but consistently applying them can be challenging when time is limited.

    If you’re looking for quick, performance-focused meals that align with your training demands, my 15-Min Performance Meals eBook is designed to help. Whether you need a carbohydrate-rich meal before a high-intensity training session, a balanced recovery meal after a match, or a nutritious option on lighter training days, you’ll find practical recipes that can be prepared in just 15 minutes.

    The eBook contains over 40 athlete-friendly recipes developed to support performance, recovery and everyday fuelling, making it easier to translate the principles of nutrition periodisation into your weekly routine.

    Ready to fuel smarter? Explore the 15-Min Performance Meals eBook and start putting your nutrition plan into action today.

    Get yours here!

    15min Performance Meals

    Put Nutrition Periodisation into Practice

    Understanding the principles of nutrition periodisation is one thing but consistently applying them can be challenging when time is limited.

    If you’re looking for quick, performance-focused meals that align with your training demands, my 15-Min Performance Meals eBook is designed to help. Whether you need a carbohydrate-rich meal before a high-intensity training session, a balanced recovery meal after a match, or a nutritious option on lighter training days, you’ll find practical recipes that can be prepared in just 15 minutes.

    The eBook contains over 40 athlete-friendly recipes developed to support performance, recovery and everyday fuelling, making it easier to translate the principles of nutrition periodisation into your weekly routine.

    Ready to fuel smarter? Explore the 15-Min Performance Meals eBook and start putting your nutrition plan into action today.

    Related Articles:

    https://cc-nutrition.co.uk/2026/07/12/nutrition-periodisation-in-football/

    https://cc-nutrition.co.uk/2026/07/22/healthy-eating-vs-eating-for-performance-why-theyre-not-the-same-thing-and-why-thats-ok/

    References

    Areta, J.L. and Taylor, H.L. (2021) ‘Low energy availability and physiological downregulation in sport’, Journal of Applied Physiology, 130(6), 1683–1695.

    Burke, L.M. et al. (2021) ‘Carbohydrates for training and competition in team sports’, Journal of Sports Sciences, 39(1), 1–20.

    Collins, J. et al. (2025) ‘Energy expenditure and intake in professional male soccer players measured using doubly labelled water’, International Journal of Sport Nutrition and Exercise Metabolism.

    Guisado-Cuadrado, M. et al. (2026) ‘Biochemical responses to low energy availability in athletes: systematic review’, Scandinavian Journal of Medicine & Science in Sports.

    Mountjoy, M. et al. (2023) ‘IOC consensus statement on Relative Energy Deficiency in Sport (RED-S)’, British Journal of Sports Medicine, 57(17), 1073–1097.

    Purcell, L. (2013) ‘Sport nutrition for young athletes’, Paediatrics & Child Health, 18(4), 200–202.

    Smavik Dasa, M. et al. (2022) ‘Energy intake and availability in elite female footballers’, BMJ Open Sport & Exercise Medicine, 9(1), e001553.

    Tenforde, A.S. et al. (2021) ‘Relative energy deficiency in sport in male athletes’, Current Sports Medicine Reports, 20(7), 330–336.