Runners have a reputation for going to extremes to improve their performance. Odd eating patterns and superstitions are legendary within the sport. As the field of sports medicine continues to expand, trial and error is being replaced by scientific research. Researchers continue to bring us closer to determining the conditions and factors that lead to peak performance.
One such study, from the Nutrition Program and the Sports Medicine Institute, School of Medicine and Biomedical Sciences, Buffalo, New York, focuses on the effects of dietary fat on runners. Traditionally, runners have maintained extremely lean physiques. By restricting fat in favor of carbohydrates, however, this study suggests they may be adversely affecting their performance. Highly fit runners performed two treadmill tests following three different dietary conditions: their normal diet, a high-fat diet for seven days (38 percent fat), and a high carbohydrate diet for seven days (73 percent carbohydrate). The high fat and high-carbohydrate diets contained approximately 3,500 calories each, based on estimated energy expenditure. This was considerably more than the food the runners normally consumced. After each seven-day period, the runners were tested to determine aerobic capacity and running time to exhaustion. The subjects performed the poorest on both tests after following their normal diet. Interestingly, the runners experienced an increase in aerobic capacity and were able to run longer after following the high-fat diet. After following the high carbohydrate diet, the runners performed better than after their normal diet but, not as well as after the high fat diet.
Researchers attribute these improvements to the fact that a higher fat diet increases the availability of free fatty acids. Past studies have shown that as an individual becomes more fit, they are better able to use fat for energy during exercise. When utilizing dietary fat as an available energy source, the runners were able to run harder for a longer period of time.
Loading Up Free Fatty Acids
But what about carbohydrate loading? Don’t you need a lot of carbohydrates for endurance? Maybe not as much as was previously thought. Many of the studies that focused on the benefit of a high carbohydrate diet on endurance were conducted using moderately trained or untrained individuals. These results may have little significance to the well conditioned athlete, particularly since endurance training has been shown to affect the way we metabolize fuel during exercise.
Further investigations are needed into the metabolic processes of exercise. While the authors of this study are quick to point out that, for health reasons, fat intake should not exceed 35% of totatl nutrient intake, it may be that athletes who severely restrict theiir intake of fat may be adversely affecting their performance.
Daryl Conant, M.Ed.