Carbohydrate-loading diet

Definition

A carbohydrate-loading diet, also called a carb-loading diet, is a strategy to increase the amount of fuel stored in your muscles to improve your athletic performance for endurance events.

Carbohydrate loading is a result of continuing to eat a high-carbohydrate "training diet" while scaling back your activity level during carbohydrate loading.

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 to complete an endurance event with less fatigue, improving your athletic performance.

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

The role of carbohydrates

Carbohydrates, also known as starches and sugars, are your body's main energy source. Complex carbohydrates include legumes, grains and starchy vegetables, such as potatoes, peas and corn. Simple carbohydrates are found mainly in fruits and milk, as well as in foods made with sugar, such as candy and other sweets.

During digestion, your body breaks down carbohydrates into sugar. The sugar enters your bloodstream, where it's then transferred to individual cells to provide energy. Sugar is stored in your liver and muscles as glycogen — your energy source.

Increase your energy storage

Your muscles normally store only small amounts of glycogen — enough to support you during recreational exercise activities. If you exercise intensely for more than 90 minutes, your muscles may run out of glycogen. At that point, fatigue might set in, and your performance may suffer.

But with carbohydrate loading, you may be able to store up more energy in your muscles to give you the stamina to make it through longer endurance events. You still will need to consume some energy sources during your event.

Carbohydrate loading

Carbohydrate loading is done the week before a high-endurance activity: Three to four days before the event, increase your carbohydrate intake to about 10 to 12 grams of carbohydrate per kilogram of body weight (70 percent of your daily calories). Cut back on foods higher in fat to compensate for the extra carbohydrate-rich foods.

Also scale back your training. Rest completely the day before your big event. The combination of eating more carbohydrates and tapering activity appear to improve muscle glycogen stores. 

How many carbs you need depends on your total calorie goal as well as your sport. For most athletes, 5 to 7 grams of carbohydrate per kilogram of weight daily is right for general training. However, endurance athletes may need up to 12 grams per kilogram. (1 pound equals 2.2 kilograms.)