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Body mass (BM) or fat mass (FM) reduction in athletes is generally motivated by a desire to either achieve a predetermined weight to compete in a specific weight class or category (e.g. horse racing, lightweight rowing, combat sports, weightlifting) or a specific body composition to enhance performance by improving physiological variables such as economy of movement (Bunc 2000) or thermoregulation (Dervis et al. 2016). Furthermore, in sports like gymnastics, diving and figure skating, attainment of a desired physical aesthetic is still considered important (Douda et al. 2008). Adding to these performance issues are current societal trends that encourage the pursuit of leanness for both men and women (Tantleff-Dunn et al. 2011). Unfortunately, the expectation of leanness has become increasingly important in sports where an image of physical attractiveness is desired for promotion or advertising. Athletes, or the sport itself, frequently derive substantial financial rewards for delivering an image and wearing clothing that accentuates physique (Simmers et al. 2009).

Given higher total daily energy expenditure (Burke et al. 2003), it could be presumed that athletes’ heavy training loads (and thus exercise energy expenditure) protects them from achieving the positive energy balance to drive FM gain. While this may be so during intensified training blocks, periods of moderated training loads such as pre-competition training tapers (Mujika et al. 2004), injury (Myer et al. 2014) and off-season breaks (Bilsborough et al. 2017) facilitate sufficient FM gain to warrant subsequent interventions aimed at weight and fat loss.

Despite the apparent preoccupation with body fat and weight in many athletes, there is surprisingly limited empirical evidence describing the impact of body composition on performance. While greater FM does predict poorer performance outcomes in gravitational endurance sports like distance running (Tanda & Knechtle 2013; Alvero-Cruz et al. 2019), triathlon (Landers et al. 2000), cross-country skiing (Larsson & Henrikkson-Larsen 2008; Stöggl et al. 2010) and road cycling (Haakonssen et al. 2016), the effect is not uniform across gender (Knechtle et al. 2011) or levels of adiposity (Tanda & Knechtle 2015). As success in competitive sport is often decided by exceptionally small margins, testing the independent effect of specific physique adaptations relative to other factors such as talent and training is difficult. Furthermore, at the elite level, the range of specific physique attributes within a sport is quite narrow. Research to test the influence of change in BM and/or FM on performance adaptations therefore has to be carefully designed using measures sensitive enough to assess the independent contribution of physique to competition success. Definitive justification that FM loss will enhance performance of athletes is often lacking. Decision-making regarding the best path for athletes requires the combined expertise of athlete, coach and sports dietitian.

While there may be a ...

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