As athletes seek to boost their training and performance, they look to specific energy sources such as carbohydrate and fat. Traditionally, increasing dietary carbohydrate to about 60% of daily energy intake has been successful in heightening the training intensity and endurance of long distance runners and cyclists. Some but not all studies of endurance athletes have found that increasing fat, rather than carbohydrate, intake promoted endurance. We examined the effects of diets high (about 50% energy intake) in carbohydrate, saturated fat and polyunsaturated fat on the performance of elite cyclists. We found no effect of diet on the capacity of the cyclists to perform maximal exercise. Endurance, however, was impaired by the polyunsaturated fat diet. Additionally, the polyunsaturated fat diet increased body losses of iron and zinc with a lesser effect on magnesium; it also tended to decrease body iron stores, particularly in one cyclist who had the greatest decrement in endurance on the polyunsaturated fat diet. The inconsistent effect of dietary fat on endurance performance may be explained by the type of dietary fat composition and an adverse effect of polyunsaturated fat on iron metabolism. These findings support the consumption of a varied diet that contains whole foods by athletes in training and in preparation for competition. This information will be useful for dietitians and sports medicine professionals who counsel physically active people.
© Copyright 2001 International Journal of Sport Nutrition and Exercise Metabolism. Human Kinetics. Alle Rechte vorbehalten.