Low-carbohydrate diets for athletes: what evidence?

Exercise scientists teach that since muscle glycogen utilisation occurs at high rates (during high-intensity exercise in carbohydrate-adapted athletes), all athletes must be advised to ingest large amounts of carbohydrate before and during exercise. 2 But this does not seem entirely logical. Why, for example, should athletes involved in prolonged submaximal exercise—probably the most common form of exercise performed by most elite and recreational athletes in training and competition—need always to eat highcarbohydrate diets in which at least 40–60% of calories are derived from carbohydrates? Surely our abundant body fat stores could provide most if not all the energy necessary to fuel activities of a submaximal intensity? Might our ability to use fat as a fuel during most activities explain the opinion that ‘a conclusive endorsement of a high-carbohydrate diet (for improved athletic performance) based on the literature is difficult to make’.