Protein
The protein requirements of athletes, once the source of great controversy, has settled into a current consensus. Sedentary people and recreational athletes[17] have similar protein requirements, about 1 gram of protein per kilogram of body mass. These needs are easily met by a balanced diet containing about 70 grams of protein for a 70 kg (150 pound) man or 60 grams of protein for a 60 kg (130 pound) woman.
People who exercise at greater intensity, and especially those whose activity grows muscle bulk, have significantly higher protein requirements. According to Clinical Sports Nutrition (see footnote above), active athletes playing power sports (such as football), those engaged in muscle-development training, and elite endurance athletes, all require approximately 2 grams of protein per day per kilogram of body weight, roughly double that of a sedentary persons. Older athletes seeking primarily to maintain developed muscle mass require 2 to 3 g/day/kg.
Protein intake in excess of that required to build muscle (and other) tissue is broken-down by gluconeogenesis to be used as energy.
The most recent evidence appears to support the beneficial nature of a high-protein, low-carbohydrate diet. A large randomized study at Stanford University found that women following such a diet “lost more weight and experienced more favorable overall metabolic effects at 12 months” than in other diets. The study followed 311 pre-menopausal, non-diabetic women, age 25-50. The women lost significantly more weight (mean 4.7 kg) on the Atkins diet than on 3 higher-carbohydrate diets (LEARN 2.6 kg, Ornish 2.2 kg, and Zone 1.6 kg), without appearing to increase cardiovascular risks within the 12-month study period. Changes in HDL cholesterol, triglycerides, and mean blood pressure significantly favored Atkins over the other three diets. The authors concluded that “concerns about adverse metabolic effects of the Atkins diet were not substantiated within the 12-month study period.”[18]