Fat intake in bodybuilding

Bodybuilders and other athletes typically believe that low fat intake results in lower body fat and better performance and thus typically consume very low-fat diets. However, in physically active athletes consuming adequate calories, no correlation has been observed between fat intake and percent body fat and therefore, restricting fat intake may not be advisable.

 Fat is an important source of energy for light- and moderate-intensity activity and during long-duration aerobic activity. At least 20% energy should be provided by fat in the diets of athletes, given the role of fat in providing energy for athletes involved in prolonged, low-intensity activity. Restricting fat intake to less than 15% of energy intake is not advisable because it will not only limit performance by inhibiting intramuscular triglyceride storage, which is a significant source of energy during activities of all intensities, but will also affect important physiological functions.

Protein intake in strength and endurance exercises

Heavy resistance exercise stimulates muscle growth, however, increasing dietary protein has not been shown to be necessary for maximum muscle development in the bodybuilding. RDA for protein (0.8 g/kg body weight/d) has been determined using sedentary individuals. An adequate energy intake can ensurethe efficient use of dietary protein, but inadequate intake of energy will result in the use of protein to meet the energy needs of activity.

Dietary protein intake in excess of the current RDA may be required for optimal muscle growth, especially for individuals involved in heavy resistance-training exercises, who have been observed to require 1.7–1.8 g protein/kg body weight/d. However, benefits of high protein intake have been observed to plateau at intake levels well below those typically consumed by athletes. Intakes greater than 2 g/kg body weight/d have not been shown to be beneficial to strength athletes and their performance benefits are unproven at the present time, contrary to popular myth among bodybuilding society .

Protein and carbohydrates

Certain amino acids are effective secretagogues of insulin and have been found to synergistically increase the blood insulin response to a carbohydrate load when administered in combination (Floyd et al. 1966; Fajans et al. 1967). Of the 20 amino acids normally found in protein, the most effective insulin secretagogue is arginine (Fajans et al. 1967). When infused with carbohydrate, arginine has been found to increase the insulin response fivefold above that produced by the carbohydrate or arginine alone. However, we have found the use of amino acids to be impractical when added to a carbohydrate supplement because they produce many unwanted sideeffects such as mild borborygmus and diarrhoea. Protein meals and supplements also have been found to enhance the insulin response to a carbohydrate load and do not produce the unwanted side-effects of the amino acids (Rabinowitz et al. 1966; Pallota & Kennedy 1968; Spiller et al. 1987). For example, Spiller et al. (1987) demonstrated a nincreased blood insulin response and decreased blood glucose response with the addition of protein to a 58 g carbohydrate supplement. The insulin response was found to be directly proportional and the glucose response inversely proportional to the protein content of the
carbohydrate–protein supplement. No adverse side-effects were reported.