Caloric restriction occurs when athletes attempt to reduce body fat or make weight. There is evidence that protein needs increase when athletes restrict calories or have low body fat.
Purpose: The aims of this review were to evaluate the effects of dietary protein on body composition in energy-restricted resistance-trained athletes and to provide protein recommendations for these athletes.
Methods: Database searches were performed from earliest record to July 2013 using the terms protein, and intake, or diet, and weight, or train, or restrict, or energy, or strength, and athlete. Studies (N = 6) needed to use adult (≥ 18 yrs), energy-restricted, resistance-trained (> 6 months) humans of lower body fat (males ≤ 23% and females ≤ 35%) performing resistance training. Protein intake, fat free mass (FFM) and body fat had to be reported. Results: Body fat percentage decreased (0.5% to 6.6%) in all study groups (N = 13) and FFM decreased (0.3 to 2.7kg) in nine of 13. Four groups gained or did not lose FFM. They had the highest body fat, smallest magnitudes of energy restriction or underwent novel resistance training stimuli. Two groups lost non-significant amounts of FFM. The same conditions that existed in the groups that did not lose FFM existed in the first group. These conditions were not present in the second group, but this group consumed the highest protein intake in this review (2.5-2.6g/kg).
Conclusions: Protein needs for energy-restricted resistance-trained athletes are likely 2.3-3.1g/kg of FFM scaled upwards with severity of caloric restriction and leanness