Carbohydrate loading, commonly referred to as carb-loading, or carbo-loading, is a strategy used by endurance athletes, such as marathoners and triathletes, to maximize the storage of glycogen (or energy) in the muscles and liver.

Carbohydrate loading is generally recommended for endurance events lasting longer than 90 minutes. Foods with low glycemic indices are generally preferred for carbo-loading due to their minimal effect on serum glucose levels. Low glycemic foods commonly include vegetables, whole wheat pasta, and grains. Many endurance athletes have large pasta dinners the night before an event. Since muscles also use amino acids extensively when functioning within aerobic limits, meals should also include adequate protein. Large portions before a race can, however, decrease race-day performance if the digestive system has not had the time to process the food regimen.