To have a ready supply of energy for your workouts, you should eat carbohydrate-rich foods about an hour before exercising. Try a mix of complex carbohydrates (think whole-wheat breads, grains) and simple sugars (think fruits). The amount of food you eat depends on the kind of exercise:
For MODERATE EXERCISE: Eat about 2 calories per pound of body weight.
For ENDURANCE ACTIVITIES (over 60 to 90 minutes): Eat between 100 and 300 calories per HOUR of planned exercise.