Low glycemic index foods are useful before exercise and high glycemic index foods are good after exercise.
The glycemic index of a food is a relative measure of how fast that food is broken down. A low glycemic index means slow break down, and a high glycemic index indicates fast metabolism of the food, with glucose having the highest glycemic index of 100.
Low glycemic index foods before exercise help to provide a steady source of energy during the exercise session, and high glycemic index foods quickly replenish the energy that was lost during exercise.