Should I carb load?

Carbohydrates are essential fuel for muscles and provide a source of quick energy. But is it true that eating extra carbs before an athletic event or mission will improve your performance? Carbs becomes especially important when you put your body to test during athletic competitions and events. If your body’s available carbs run out, fatigue sets in and you can “hit the wall.” To avoid this, many athletes load up on extra carbs such as bread, pasta, and rice. Read more about the concept behind carb loading and how it can affect your performance.


The idea of intentionally increasing carbs, or “carb loading,” prior to an athletic event or competition started in the 1960s. Classic carb-loading protocols involve 3–6 days of eating a high amount of carbs while tapering down exercise. The theory behind carb loading is that it increases muscle glycogen (the form in which the body stores glucose) above normal levels, thus delaying fatigue and improving performance when your body makes extra demands.

Can you increase muscle glycogen?

Carb loading can increase muscle glycogen above normal levels, also referred to as “glycogen supercompensation.” Variables such as the amount of carbs you eat per day, the number of days you carb load, and the type and amount of exercise you do on carb-loading days affect the degree of muscle glycogen supercompensation. In turn, the amount of supercompensation affects your performance. Muscle glycogen remains elevated for up to 5 days following a carb-loading phase.

Will carb loading improve my performance?

Carb loading is most likely to improve your performance in endurance sports (events lasting longer than 90 minutes) and other activities with similar demands. Research suggests that performance in such activities can increase by as much as 2–3% when muscle glycogen levels are supercompensated. If you eat and drink the recommended amount of carbs and fluid during exercise, your body will use those sources of fuel first instead of relying solely on your glycogen stores. Even if you carb load, it’s important to follow the guidelines for fueling during exercise, because there can be other negative effects of improper fueling. Carb loading contributes little to no improvement in performance with exercise lasting less than 90 minutes.

How many carbs should I eat to “carb load”?

The amount you need to supercompensate your muscle glycogen stores is individual. It depends on your level of fitness and the duration of the event or competition. Typically, consuming 5–12 g/kg of body weight per day for at least one day before an endurance event is enough for most men to achieve glycogen supercompensation. To learn more about carb needs for your activity level, read HPRC’s “Warfighter Nutrition Guide.”

Are there any differences in carb-loading recommendations for women?

The research on carb loading in female athletes has been inconsistent, both in terms of increase in muscle glycogen and improvement of performance. However, for at least some women, 8 g/kg per day for 3–4 days will result in an increase in muscle glycogen. Female athletes also may find it helpful to increase their overall calorie intake (not just carbs) for optimal increases in muscle glycogen.

Can I overdo it on carb loading?

Consuming more carbs than the recommended 5–12 g/kg doesn’t mean higher muscle glycogen stores or a better performance. High carb intake may lead to gastrointestinal discomfort or bloating. In addition, when your body stores carbs, it stores water along with them, so you may experience (water) weight gain and feelings of fullness. As with any extra calories you eat, excess carb intake without exercise to balance it out can lead to weight gain.


Carb loading at least one day prior to an event, competition, or mission that lasts over 90 minutes can improve your performance. However, the amount your performance can improve depends on a variety of different factors. Visit the U.S. Anti-Doping Agency’s web page “Carbohydrates – The Master Fuel” to learn more about recommended intake and timing.

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