Eating before you run helps prevent hypoglycemia (low blood sugar), stave off hunger, fuel your muscles and give mental assurance that your body is well fueled. Depending on what you're running, what you eat during and after can also be very important.
Eat high-carbohydrate meals daily to keep your muscles fueled.
Avoid sugary foods, such as candy and soda, within an hour before hard exercise. Instead, choose high-starch, low-fat foods - bread, crackers and pasta - since they tend to digest easily.
Allow adequate time for digestion - three to four hours for a large meal, two to three hours for a smaller meal and less than an hour for a small snack.
Stick with liquid foods if digestion is a problem.
Eat familiar foods before a race. Don't try anything new.
Consume sports gels or sports drinks during your workout or race if you're running 90 minutes or more. Make sure you drink plenty of fluids throughout.
Replenish immediately after exercise with a glass of juice or other high-carbohydrate foods. Follow up with a high-carbohydrate meal, especially after a race or hard workout.