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.)
