Rule 2. Let Form Follow Function
Maintaining your ideal body weight is important for all-around health, whether you're an athlete or a couch potato. For athletes, staying lean is also important for performance. Your best body weight at optimal health is also your best body weight for sports and exercise performance.
That's good news, because it gives you a simple way to determine how much you should eat each day. Instead of counting calories, which can be tedious and inaccurate, monitor your performance in workouts. If you follow a sensible, progressive training program, your fitness will gradually improve from week to week—unless you're eating too many calories per day or not enough.
Stagnating performance coupled with rapid weight loss is a likely indication of underfueling, while stagnating performance coinciding with steady or increasing weight may mean you're getting too many calories. In either case, a slight adjustment to your daily eating amounts should put you quickly back on track.
Rule 3. Balance Your Energy Sources
Athletes often make the mistake of overemphasizing one macronutrient—carbohydrates, fats or proteins—at the expense of the other two. All are equally important.
Carbs should account for at least 50 percent of the total calories in your diet. If you eat less you may experience low energy in workouts due to insufficient stores of glycoge—a carbohydrate-derived fuel—in your muscles.
Fats should account for at least 20 percent of your daily calories (more healthy monounsaturated and polyunsaturated fats, like nuts and olive oil, than saturated). One study found that runners who consumed too little fat were more susceptible to injuries.
Finally, at least 15 percent of your daily calories should come from protein. Inadequate protein intake will compromise your recovery from workouts and limit the amount of training you can handle without getting sick or injured.
So, what makes up the remaining 15 percent? The distribution of these calories—whether more carbs, fats or proteins—should depend on what works best for you and can vary from day to day without negative consequences.
Rule 4. Gorge on Free-radical Fighters
Free radicals are unstable molecules that attack and damage cells. Due to the high rate of oxygen consumption associated with exercise, athletes experience more free-radical stress than sedentary people. The muscle-repair process that occurs after workouts releases even more free radicals.
Fortunately, exercise also strengthens the antioxidant system the body uses to prevent and limit free-radical damage. But your antioxidant defenses won't work to their full potential unless you maintain a diet that's rich in antioxidants—which means one that includes lots of fruits and vegetables. In addition to aiming for seven to nine servings daily, try to eat a wide variety of different fruits and vegetables. Each has its own unique antioxidant profile that benefits the body somewhat differently than others.