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Dec. 22, 1999 (Atlanta) -- Usually, when fat and exercise are mentioned together, it has to do with losing extra pounds. However, a new study from Scotland shows that consuming extra fat -- at least by athletes in tiptop shape -- can enhance athletic endurance. "We discovered that raising the circulating levels of FFAs [free fatty acids] immediately prior to exercise can increase the capacity to perform prolonged exercise in endurance-trained individuals," lead author Yannis Pitsiladis, MD, tells WebMD.

According to The Nutrition Bible, by Jean Anderson and Barbara Deskins (William Morrow and Company), FFAs are by-products of fat and are usually formed when the fats in butter, lard, margarine, or cooking oils are digested and transported within the body.

In the study, the researchers sought to clarify the relationship between carbohydrates and fat oxidation during exercise. Their research was based on the understanding that the biggest reason for fatigue during exercise is the depletion of stored carbohydrates by muscles.

"Depletion of muscle glycogen is widely considered to be the most likely candidate limiting prolonged exercise performance," Pitsiladis tells WebMD. "There has been much research interest directed toward finding ways of 'sparing' muscle glycogen in order to delay muscle fatigue."

For years, marathoners and other endurance athletes have practiced "carbohydrate loading" based on this premise. According to Ellen Coleman, RD, when carbohydrates are consumed, the body changes much of it into glucose, the chief source of energy for the body. Glucose that is not needed immediately is stored as glycogen in the liver and muscles for later use. "Although eating carbohydrates 30 to 45 minutes before exercise raises insulin levels and lowers blood glucose, these effects are temporary and will not harm performance," write Coleman and colleagues in the February 1997 issue of The Physician and Sportsmedicine. "In fact, consuming carbohydrates an hour before exercise can improve performance. Carbohydrate feedings 3 to 4 hours before exercise also enhance performance by 'topping off' glycogen stores."

Pitsiladis says that fat may enhance performance even more. Pitsiladis, who is a professor at the Exercise Physiology Center for Exercise Science and Medicine at University of Glasgow in Scotland, says this new study was the first in humans to examine the effects of increased FFA availability on exercise performance.

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