Essential question. Great, S.P.
Studies show that hard exercise damages muscles, but also that the healing process is what makes them stronger than before. The key to helping them rebuild quickly and improve performance is:
A) Eat carbs and protein as soon as possible after a workout, and
B) Rest between workouts.
This combined approach works best when trying to improve performance. Some people train too much.
Also, there is a "window" of about four hours after exercise during which carbs are stored more efficiently into the muscles; this window is actually "open widest" during the period soonest after exercise. So eat protein and carbs as soon as possible.
And supplements are fine in moderation. But a poor diet with supplements is still a poor diet. Everyone, especially athletes, should try to get as much of their vitamins, minerals and phytochemicals from fresh fruits and vegetables as possible. There are many naturally occuring nutrients in them which prevent disease and promote health which we are only beginning to understand. People who take large amounts of supplements may be unbalancing their systems.
A study of the antioxidant, beta carotene, was conducted to test its effectiveness against cancer. Suprisingly, cancer rates increased in those who took beta carotene supplements. It was later discovered that beta carotene, when taken excessively, depletes the body of vitamin e, another cancer-preventing substance. The bottom line is, stay balanced and don't overload on supplements, but eat a variety of foods.
As for fat, some is recommended in the diet of an athlete. Caloric intake of 25% fat out of the total calories eaten is about average. It is suggested that fat is more readily metabolized from fatty foods than from fat stores and that no matter how hard you exercise, you will always need to "burn" a certain amount of fat. So if you don't eat enough fat, your body will have to get it from your fat stores, which may not be released rapidly enough to ensure top performance.
See also www.halcyon.com/gasman/toc.htm#nuttips