Proteins come in meats, fish, poultry, eggs, beans, nuts, dairy products and other foods, and should provide approximately 12-15 percent of daily calories. Proteins give your body power to build new tissues and fluids, among other functions. Your body cannot store extra protein, so it burns it for energy or converts it to fat. The amount of protein an athlete needs depends in part upon level of fitness; exercise type, intensity and duration; total calories; and carbohydrate intake.
Level of fitness: Physically active people need more protein compared with those who don't exercise. You also need more when you start an exercise program.
Exercise type, intensity and duration: Endurance athletes often burn protein for fuel, as do body builders and others doing intense, strength-building activities.
Total calories: Your body burns more protein if you don't consume enough calories to maintain body weight. This can happen if you eat too little or exercise too much.
Carbohydrate intake: Your body may use protein for energy if you exercise with low levels of muscle glycogen or if you do repeated training sessions without eating more carbohydrates. When you start with enough muscle glycogen, protein supplies about 5 percent of energy. Otherwise it may supply up to 10 percent.
