Energy Intake
The first component to optimize training and performance through nutrition is to ensure the athlete is consuming enough calories to offset energy expenditure [1, 6-8]. People who participate in a general fitness program (e.g., exercising 30 - 40 minutes per day, 3 times per week) can typically meet nutritional needs following a normal diet (e.g., 1,800 – 2,400 kcals/day or about 25 - 35 kcals/kg/day for a 50 – 80 kg individual) because their caloric demands from exercise are not too great (e.g., 200 – 400 kcals/session) [1]. However, athletes involved in
moderate levels of intense training (e.g., 2-3 hours per day of intense exercise performed 5-6 times per week) or high volume intense training (e.g., 3-6 hours per day of intense training in 1- 2 workouts for 5-6 days per week) may expend 600 – 1,200 kcals or more per hour during
exercise [1, 9]. For this reason, their caloric needs may approach 50 – 80 kcals/kg/day (2,500 – 8,000 kcals/day for a 50 – 100 kg athlete). For elite athletes, energy expenditure during heavy training or competition may be enormous. For example, energy expenditure for cyclists to compete in the Tour de France has been estimated as high as 12,000 kcals/day (150 - 200 kcals/kg/d for a 60 – 80 kg athlete) [9-11]. Additionally, caloric needs for large athletes (i.e., 100 – 150 kg) may range between 6,000 – 12,000 kcals/day depending on the volume and intensity of different training phases [9]. Although some argue that athletes can meet caloric needs simply by consuming a wellbalanced
diet, it is often very difficult for larger athletes and/or athletes engaged in high volume/intense training to be able to eat enough food in order to meet caloric needs [1, 7, 9, 10, 12]. Maintaining an energy deficient diet during training often leads to significant weight loss
(including muscle mass), illness, onset of physical and psychological symptoms of overtraining, and reductions in performance [8].