Eating a light snack before exercise may actually increase your fat-burning potential. Pick a small snack like piece of fruit, a sports beverage or some fruit juice.  If you eat a large meal, wait about four hours before you exercise. If you eat a regular meal, you only have to wait about two hours to work out. Your body prefers to use carbohydrates as fuel, so your pre-workout meal should include plenty of complex carbohydrates from 100% whole grain bread or pasta, and plenty of fruits and vegetables. You don't need to avoid protein and fat, however don't choose large portions of meats and fact foods if you will be exercising in an hour or two.