Purpose

Any physical activity requires carbohydrates for fuel. For most recreational activity, your body uses its existing energy stores for fuel.

But when you engage in long, intense athletic events, your body needs extra energy to keep going. The purpose of carbohydrate loading is to give you the energy you need to complete an endurance event with less fatigue, improving your athletic performance.

Carbohydrate loading may be most beneficial if you're an endurance athlete — such as a marathon runner, swimmer, cyclist or all three — preparing for an event that will last 90 minutes or more. Other athletes generally don't need carbohydrate loading. It's usually enough to get about half of your calories from carbohydrates.