Carbohydrate Loading

Christopher D. Jensen, PhD, MPH, RD
Carbohydrate loading is a fueling strategy designed to maximize an athlete’s muscle glycogen levels before an endurance event. Read this article to help you better understand how carbohydrate loading works in relation to muscle glycogen levels, when to use it and when not to, where athletes typically go wrong, and practical strategies for how to best make it work for you.

Many athletes are familiar with the term “carb loading” to describe everything from the pasta feed the night before a fun run to overeating pre‐race. Traditional carbohydrate loading methods typically occur in a 7 day period. However, recent studies have shown that carbohydrate loading can occur over a much shorter period than originally thought.

In a 2002 study (Bussau), researchers found that carb loading (supercompensation of glycogen stores) can occur sooner than three days in athletes who have maintained their muscle glycogen stores. In this study, athletes followed their normal training regimen on day one. On the morning of day two, their muscle glycogen levels were measured, and then they began consuming a carbohydrate based diet while resting for three consecutive days. Researchers found that 24 hours after the athletes began consuming a carbohydrate‐based diet, muscle glycogen levels peaked and did not increase any further with continued rest and two additional days of carbohydrate intake.

Tips You Should Know for Your Carb Loading –
  1. When to do it – You should consider carb loading as a part of your nutritional strategy if you are competing in an athletic event lasting 90 minutes or longer.
  2. Possible Weight Gain – You may see a temporary increase in weight if you have effectively loaded.
  3. How long does it last – You can maintain complete carb loading for as many as 5 days leading up to your event or competition. Continue eating a carbohydrate‐based diet and engage only in light exercise.
Don’t make the mistake of not eating enough carbohydrates. Make sure you are eating enough carbs to gain all its benefits. For a 1‐ to 3‐day carbohydrate load, consume 4.5 grams of carbohydrates per lb (10g/kg) of bodyweight per day. The carbohydrate‐based foods should be high‐glycemic, and you should be relatively inactive during the loading process.

Does it really work - and when do you use it? Carbohydrate loading does work. Typically, if you are exercising at a steady pace and intensity, carbohydrate loading will increase your endurance by about 20%. For example, if you typically can run 20 miles before exhaustion gets the better of you, with supercompensated glycogen stores you may be able to extend that to 24 miles. Or, if your event calls for you to cover a specific distance, such as is the case with a cycling race or a marathon, carbohydrate loading may improve your time by 2-3%. For a four-hour race, that equates to about 5-7 minutes faster.

Eating this much requires some preparation, so take a look at the following example of a carb loading nutrition plan for a 150‐pound (68 kg) athlete striving to consume 4.5g of carbohydrate per lb (10 g/kg):


Breakfast

2 cups dry breakfast cereal (48g carbs)

1 cup nonfat milk (12g carbs)

1 banana (27g carbs)

2 halves toasted English muffin with 2 tbs. strawberry jam (25 + 26g carbs)

8 oz orange juice (26g carbs)
...................................................................................................164g carbs


Snack

1 PowerBar® Performance Energy bar (45g carbs)

1 cup of fresh fruit salad (32g carbs)

8oz PowerBar Perform™ Sports Drink (17g carbs)
...................................................................................................94g carbs


Lunch

1 turkey sandwich with 2 slices sourdough bread (30g carbs)

1 cup fresh or canned fruit (32g carbs)

16oz PowerBar Perform™ Sports Drink (34g carbs)
...................................................................................................96g carbs


Snack

16oz fruit smoothie (62g carbs)

5 saltine crackers (11g carbs)
...................................................................................................73g carbs


Dinner

2 cups noodles with stir-fried chicken (80g carbs)

1 cup broccoli (10g carbs)

1 cup fresh fruit (32g carbs)

20oz soft drink (68g carbs)
...................................................................................................190g carbs


Snack

1 PowerBar® Performance Energy bar (45g carbs)

8oz PowerBar Perform™ Sports Drink (17g carbs)
...................................................................................................62g carbs


Total: ...................................679g carbs


References:
Academy of Nutrition and Dietetics Sports Nutrition Care Manual. What is carbohydrate loading? Why, when, and how it is used?

Bussau VA, Fairchild TJ, Rao A, Steele P, Fournier PA. Carbohydrate loading in human muscle: An improved 1 day protocol. Eur J Appl Physiol. 2002;87(3):290‐295.

Burke, L. Middle‐ and long‐distance running. In: Practical Sports Nutrition. Human Kinetics Australia, 2007; 109–139.

Burke, L. Preparation for competition. In: Burke L, Deakin V. Clinical Sports Nutrition. 3rd ed. McGraw‐Hill, 2006; 355–384.

Coleman, EJ. Carbohydrate and exercise. In: Dunford, M., ed.: Cardiovascular and Wellness Nutritionists’ Dietetic Practice Group. Sports Nutrition — A Practice Manual for Professionals. 4th ed., American Dietetic Association, 2006; 14–3.
About The Author

Dr. Jensen manages health-related research studies at the Kaiser Permanente Division of Research in Northern California. He is also a sports nutrition writer and has years of experience in the design and testing of sports nutrition products. Dr. Jensen is a recreational runner and former basketball player.

Fun Fact: Chris loves running on the beach and playing the drums.

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