Forget weight watching. A new study shows that a high-fat diet can help female athletes literally go that extra mile.
Eighteen women soccer players at the State University of New York went more than two kilometres further before reaching exhaustion on a diet of 35 percent fat.
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"That is really a striking difference," says Horvath, an associate professor at SUNY.
Diets
Women in the study went on three different diets during the second half of three menstrual periods. One month, six women were on a normal diet; another six ate a normal diet plus 415 calories of oil-roasted peanuts a day, and the remainder ate the normal diet plus an equal amount of extra calories from carbohydrate-rich energy bars. Each group switched the following month so that after three months, all had been tested on each of diet.
Each diet was tested for seven days during the luteal phase (the second half) of the menstrual cycle, when a woman's ability to metabolise fat is the greatest.
The peanut diet included 35 percent of calories from fat, compared with 24 percent on the energy-bar diet. The normal diet had 27 percent fat.
The energy-bar diet contained 63 percent carbohydrates, compared to 51 percent on the peanut diet. Protein and calorie intake and caloric expenditure were essentially the same in all three diets.
Endurance tests
The endurance tests used three running methods: constant-speed, running at different rates on a treadmill and forward running with a side-step manoeuvre performed on a force plate. The athletes were tested until exhaustion on the seventh day of each diet.
The results showed that team members travelled 11.2 kilometres on the high-fat diet, 10 kilometres on the normal diet and 9.7 kilometres on the high-carbohydrate diet. Muscle performance, measured by the force plate, remained the same.
"Outside of planning a lot of meals during the season, we stick to having our runners eat well and get the proper mix of carbohydrates and fats. This information isn't dangerous or a fad. It's an easy thing to pass along to athletes," McCarthy says.
Women benefit
Horvath says a high-fat diet seems to be more of a boost to women than to men, based on previous studies he has done with male athletes.
"Men responded to calories, but women responded to fat," he says.
As a result of his findings, he says, "Any research that had been done on men has to be redone for females. Dietary recommendations for women athletes should be different from men's."
"An athletically fit woman's fat intake in her diet should be about 25 percent," says St. Louis dietician and personal trainer Ellie Zografakis. But she says there is no harm in higher fat intake for athletes, because endurance exercise is a very efficient use of fat.
Energy
"With a diet of 35 percent fat fuel, the athletes would have more energy and feel more powerful," she says. However, she warns against increasing the fat intake by lowering the carbohydrate intake too much. An intake below 50 percent would be inadequate for performance.
Zografakis says, in fact, most of her clients don't get enough fat; only 10 to 20 percent of their calories come from fat, which she says is too low.
"Fat is seen as taboo for all women. They are not willing to increase their fat intake," she says.
Instead, she says many women have a high carbohydrate intake - as much as 80 percent of their diet - which can cause bloating along with a lack of energy.
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