May 24, 2024

Carb loading is a method that has been used for at least 20 years now by marathon runners and other endurance athletes. The idea behind carb loading is that you would eat a huge amount of carbohydrates, usually complex carbohydrates in the 12-18 hours before competition. The Mayo Clinic came up with this great primer on the how, what and why of Carb loading.

Carb Loading Foods
Carb Loading Foods

Carbohydrate loading can improve your performance during high-intensity endurance exercise. Use this strategy to prepare for a marathon, triathlon or another endurance event.

Perhaps you’re training for a marathon or triathlon. Or maybe you’re a long-distance swimmer or cyclist. Whatever your sport, if you plan to complete 90 minutes or more of high-intensity exercise, carbo-loading (carbohydrate loading) may improve your performance.

Carbohydrates: The body’s fuel

The food you eat contains carbohydrates, protein and fat. These nutrients supply the calories your body uses for energy. Although your body needs all three nutrients, carbohydrates are your body’s primary source of energy.

Carbohydrates are found in grains, vegetables and legumes (beans and peas). They are also found in sugar and sweets, including fruit and dairy products. Each gram of carbohydrate contains four calories.

During digestion, your body converts carbohydrates into sugar. The sugar enters your bloodstream and is transferred to individual cells to provide energy. Your body may not immediately need all of this sugar, however. So it stores the extra sugar in your liver and muscles. This stored sugar is called glycogen.

Carb loading: Store extra energy for greater endurance

Your muscles normally store only small amounts of glycogen. Usually, this isn’t a problem. But if you start exercising at high intensity, such as when running or swimming, and you continue for more than 60 to 90 minutes, your muscles run out of glycogen. As a result, your stamina and performance diminish.

Carbohydrate loading works by forcing your body to store more glycogen. You taper the amount of exercise you’re doing before a high-endurance event to conserve your body’s stores of glycogen. At the same time, you eat significantly more carbohydrates. As a result, glycogen stores in your muscles increase, which boosts your endurance.

Extra carbohydrates not necessary for the average athlete

Carb loading isn’t for every athlete. But if you want to improve your performance in a high-intensity aerobic endurance event, carbohydrate loading might help.

Long-distance running and swimming, soccer, canoe racing and triathlons are appropriate activities for carbohydrate loading. Shorter runs, such as a 5- or 10-kilometer race, lifting, and recreational biking or swimming are not.

Improve performance with Carb Loading

Carb loading works best when you’ve been on a carbohydrate-rich diet throughout your training, because during that time your body learns to more effectively use carbohydrates. Aim for a daily diet containing about 3 grams of carbohydrates for every pound you weigh.

Researchers are studying the best way to increase stores of glycogen in the muscles of endurance athletes. For example, a recent study suggests that one day of carbohydrate loading may be just as effective as three days of carbohydrate loading when no exercise was done that day.

But until researchers find the best way to increase glycogen stores, consider following these guidelines to increase your endurance. During the week before your event:

Reduce exercise. To avoid depleting glycogen stores in your muscles, cut the amount of exercise you do in half. For example, if you normally run 50 miles a week, plan to run no more than 25 miles the week before a marathon. But don’t stop exercising abruptly gradually decrease the amount you exercise throughout the week to avoid muscles stiffness. Then rest completely for a day or two before the event.

Load up on carbohydrates. Increase the amount of carbohydrates such as whole-grain pastas and breads in your diet so that they make up 60 percent to 70 percent of the calories you eat. Cut back on foods higher in fat to compensate for the extra carbohydrate-rich foods. That means fats should make up about 15 percent to 20 percent of your diet, and 10 percent to 15 percent of your daily calories should come from protein.

As a general rule, this means you consume 4 to 4.5 grams of carbohydrates per pound of body every day. For example, if you’re a 170-pound man, consume 680 to 765 grams of carbohydrates every day during the week before a high-intensity event. That’s about 3,000 calories a day from carbohydrates alone.

Even if you’ve loaded up on carbohydrates, you still need to keep them coming while you’re exercising to maintain your blood sugar levels. Try to drink 5 to 8 ounces of a carbohydrate-containing sports drink every 15 minutes while you’re exercising; drink more if it’s hot outside.

Understand the potential drawbacks of Carb Loading

Increasing the amount of carbohydrates you eat can cause certain side effects. These include:

Weight gain. It’s easy to gain when you’re carbohydrate loading because carbs help your body store extra water. Expect to gain 2 to 4 pounds if you do it properly.

Digestive discomfort. You may need to avoid or limit some high-fiber foods one or two days before your event, depending on your individual tolerance. Beans, bran and broccoli can cause gassy cramps, bloating and loose stools when you’re loading up on carbohydrates.

Blood sugar changes. Carbohydrate loading can affect your blood sugar levels if you have diabetes. So talk with your doctor or a registered dietitian about blood sugar management before you get started.

Use Carb Loading to meet your goals

Done properly, carbohydrate loading may be an effective way to get that extra edge you need to compete. If you’re uncertain about your specific carbohydrate needs, talk with your doctor, or a registered dietitian who specializes in sports medicine. He or she can help you design a strategy for carb loading that’s based on your unique situation.

6 thoughts on “Carb Loading

  1. Good article but can you please list your sources as their are hundreds of different ideas and theories on carbo loading many which contradict various parts of each other.


  2. Very good article, one thing to remember though is alot of people have the misconception that carb loading is only for very intense/endurance running (definately one of the main ones but not the only). I am myself am I Rugby Athlete (Flanker & In/Outside Center, essentially a Back though), a typical rugby game can last up to 90 min+ with no breaks your constanly running, rucking, tackling, chasing, etc. I found that after a good week of carb loading on lots of multi-grain pasta, multi-grain, and gainers with a high protien count I am not nearly as tired and fatigued as my teammates/opponents. Point being dont under estimate carb loading or think its bad to do if your not a runner, I know plenty of soccer, basketball, football players that benefit greatly from it.

  3. Great article, to which I totally relate!

    I am a runner, and carb loading is very important when preparing for long runs, especially during spring time when I simply cannot do without running outdoors at least 8 miles a day. What I noticed over time was that my thighs would swell up after a good week of loading. After some research I found out that was the water my muscles had retained so to make good/quick use of the stored glycogen when the time comes (how awesome is that?!?).

    And excessive urination follows two days after stopping on carb load, which is fine.

    VERY IMPORTANT: to get back to a more balanced meal plan after the carb-intensive event. A lot of runners make the mistake of living off of carbs alone, and over time they become deficient of just about all nutrients, reduced to skin and bones!

    1. I have to agree Nila, the problem with runners is the focus that it takes to be running daily also means that a lot of runners are very obsessive and will push their bodies harder than they should.

      for many people a high carb diet could be a problem but for runners you still need that protein and balanced diet for protein, nutrients, and muscle repair

  4. Great article. As a triathlete, I find that loading up on carbs while tapering my training 1-2 weeks before a triathlon really improves my performance and endurance

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