WASHINGTON, D.C. -- Female soccer players were able to perform longer at a higher intensity on a diet composed of 35 percent fat than on diets of 27 percent fat or 24 percent fat, researchers at the University at Buffalo have found.
The higher-fat diet, achieved by adding peanuts to the athletes' normal diet, had no effect on weight, percentage of body fat, heart rate or blood pressure, findings showed.
Peter J. Horvath, Ph.D., associate professor in the Department of Physical Therapy, Exercise and Nutrition Sciences in UB's School of Health Related Professions, presented the study here today (April 19, 1999) at the annual meeting of the Federation of American Societies of Experimental Biology.
"The women went 1.2 to 1.5 kilometers farther before reaching exhaustion while doing very-high-speed intermittent exercise when on the high-fat diet, compared to the lower-fat diets," said Horvath. "That is really a striking difference.
"Women are better fat metabolizers than men. Our earlier dietary studies with male and female competitive runners showed that while both improved their performance on a higher-fat diet, women benefited more than men. One implication of these findings is that dietary recommendations for women athletes should be different from men's," he said.
The study involved nine female collegiate soccer players who ate three diets in a randomized crossover design -- their normal diet, normal diet plus 415 calories of oil-roasted peanuts per day, or normal diet plus an equal amount of extra calories from carbohydrate-rich energy bars. The women consumed each diet for seven days during the luteal phase (the second half) of the menstrual cycle, when a woman's ability to metabolize fat is greatest, Horvath said.
Carbohydrate intake was highest -- 63 percent of total calories -- during the energy-bar diet, and lowest -- 51 percent -- during the peanut diet. Fat was highest during the peanut diet -- 35 percent -- versus 24 percent on the energy-bar diet. Protein and calorie intake, and caloric expenditure remained essentially the same across the three diets.
Endurance testing was designed to mimic soccer play, using constant speed running and running at different rates on a treadmill, plus forward running with a side-step maneuver performed on a force plate. The athletes were tested until exhaustion on the seventh day of each diet. Treadmill speed increased progressively, which meant the longer the athletes performed, the harder they had to work.
Results showed that the soccer players traveled about 15 percent farther on the peanut diet than on normal diet with or without energy bars, with no lessening of muscle performance, as measured by the force plate.
"When women consumed the high-fat diet, they performed longer at the highest intensity," Horvath said. Distances were 11.2 km on the high-fat diet, 10 km on the normal diet and 9.7 km on the high-carbohydrate diet.
"These results support our thesis that supplementing the diets of female athletes with peanuts or other fat sources can help build up their energy reserves and improve performance," Horvath said. "A low-fat diet may result in a poorer performance for women in a long, intermittently intense sport like soccer, especially during the later phase of the menstrual cycle."
Additional researchers on the study were Rita Genovese, Barbara O'Reilly, Renee Melton-Bork and Louise Gilchrist, Ph.D., all of the UB Department of Physical Therapy, Exercise and Nutrition Sciences, and John Leddy, M.D., UB clinical assistant professor of orthopaedics and assistant director of UB's Sports Medicine Institute.
The study was funded by a grant from Shear/Kershman Lab, Inc.
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