How Elite Endurance Athletes Burn Fat: A Study

Jeff Volek, professor of Human Sciences at the Ohio State University, is lead researcher on a project measuring the diets and fat-burning ability of endurance athletes. In summary, their research found that endurance athletes who eat very few carbohydrates burned more than twice as much fat as high-carb athletes during maximum exertion and prolonged exercise in a new study – the highest fat-burning rates under these conditions ever seen by researchers.

The study, the first to profile elite athletes habitually eating very low-carbohydrate diets, involved 20 ultra-endurance runners age 21-45 who were top competitors in running events of 50 kilometers (31 miles) or more.

The 10 low-carb athletes ate a diet consisting of 10 percent carbs, 19 percent protein and 70 percent fat. Ten high-carb athletes got more than half their calories from carbs, with a ratio of 59 percent carbs, 14 percent protein and 25 percent fat.

In all other respects, the athletes were similar: elite status, age, performance, training history and maximum oxygen capacity.

Volek has been studying the effects of low-carb eating – and ketogenic diets specifically – for years, particularly in the context of obesity and diabetes. But he has always been interested in how such a diet might augment physical performance and recovery. Ketogenic diets are those that reduce carbohydrates enough to allow the body to access its fat stores as the primary source of fuel. Lowering carbs and increasing fat intake leads to the conversion of fat into ketones, molecules that can be used by cells throughout the body, especially the brain, as an alternative to glucose.
The research is published online in the journal Metabolism: Clinical and Experimental.