In terms of nutrition, adolescence is an important time in establishing an individual’s lifelong relationship with food, which is particularly important in terms of the connection between diet, exercise, and body image (Desbrow et al., 2014). It is also important to recognize that athletic performance development is nonlinear, with success at junior competitions infrequently translating to success at Olympic or World Athletics Championships (Pizzuto et al., 2017).
During adolescence, adequate energy is required to meet both the growth and development needs of the individual, as well as the substrate demands associated with general physical activity, training, and competition (Aerenhouts et al., 2011). Although group estimates of energy expenditure in adolescent athletes have been reported (i.e., males ∼ 3,640 ± 830 kcal/day and females ∼ 3,100 ±720 kcal/day; Carlsohn et al., 2011), it is difficult to define the individual energy requirements of an adolescent athlete with precision due to metabolic variability within and between individuals (Petrie et al., 2004) and methodological difficulties in estimating both energy intake and energy expenditure (Burke et al., 2001). Furthermore, the energy expenditure associated with the exercise commitments of adolescent athletes may vary substantially due to many factors (e.g., training and competition load, seasonal variation, participation in more than one competitive sport, and concurrent compensatory sedentary behaviors).
The energy expended to synthesize new tissues is incorporated in measures of total energy expenditure, such as doubly labeled water. These measures indicate that the energy changes associated with physical activity and/or athletic training are likely to have a much greater influence on energy demands than the increases associated with growth (Torun, 2005 ). Despite this, it is important to acknowledge that resting metabolic rate is higher in adolescent athletes than adults, and standard predictive equations often underestimate resting metabolic rate compared with measured (up to 300 kcal/day) rate in adolescents (Loureiro et al., 2015).
The duration and intensity of exercise sessions determine carbohydrate utilization patterns and refueling requirements (Burke et al., 2017). There is little evidence to suggest that the utilization of carbohydrate in adolescents differs substantially from those of adults (Desbrow et al., 2014).
Young individuals appear to have a similar capacity to adults in dealing with thermal loads and exercise-tolerance time during exercise in the heat (Rowland et al., 2008). However, the mechanisms by which young individuals dissipate heat loads during exercise differ from those of adults (Falk & Dotan, 2008). Children and adolescents appear to rely more on peripheral blood redistribution (radiative and conductive cooling) rather than sweating (evaporative cooling) to maintain thermal equilibrium (Falk & Dotan, 2008). There is also evidence that adolescents who undertake regular training adapt by enhanced peripheral vasodilation (Roche et al., 2010), which is likely to improve non-evaporative cooling.
It appears that low energy availability (EA) in adolescent athletes undertaking heavy training is common (Muia et al., 2016). This may lead to a number of undesirable health consequences, including delayed puberty, menstrual irregularities, poor bone health, short stature, the development of disordered eating behaviors, and increased risk of injury. Furthermore, in females ≤ 14 years gynecological age, the effects of low EA may be more pronounced (Loucks, 2006).
However, increased rates of disturbed eating attitudes and behaviors are evident in sports that emphasize leanness for optimal performance (Torstveit et al., 2008). It is prudent to suggest that many adolescent athletes will require the knowledge, skills, and support to develop a healthy lifelong relationship with food. Although a number of practical methods to assess the adequacy of EA exist (Mountjoy et al., 2015), these may further serve to focus attention on restrictive dietary behaviors. Consequently, it is appropriate that professional associations advocate for the use of non-dieting strategies (Sundgot-Borgen et al., 2013) when addressing weight concerns in young athletes.
Dietary carbohydrate needs should be considered in light of the training loads and competition characteristics that are typically undertaken by adolescent athletes. These can differ from those undertaken by adult athletes in a number of ways. First, adolescent athletes may be involved with numerous organizations (e.g., schools, clubs, and regions) that create different competition frequencies and formats, such as sports carnivals, representative events, and trials. It is also common for aspiring adolescent athletes to participate in a number of different sports.
There is some evidence suggesting an increased prevalence of heat illness associated with sport and activity in younger athletes (Centers for Disease Control and Prevention, 2011). Heat illness may be influenced by poor hydration status along with other factors, such as undue physical exertion, insufficient cooling between exercise bouts, and inappropriate choices of clothing, including uniforms. Field studies indicate that adolescent athletes can experience significant deficits in fluid (> 4% body weight) during training and competition in the heat (Aragon-Vargas et al., 2013). Fluid shifts of this magnitude have the potential to effect exercise performance. It appears prudent, then, to apply the same fluid intake guidelines indicated for adult athletes (Casa et al., 2018).
Source: Desbrow et al. Nutrition for Special Populations: Young, Female, and Masters Athletes. International Journal of Sport Nutrition and Exercise Metabolism, 2019, 29, 220-227.