Researchers found that female footballers were able to perform longer at a higher intensity on a diet composed of 35% fat than on diets of 27% or 24% fat.

The researchers, from the State University of New York at Buffalo, boosted fat levels by adding peanuts to the footballers' normal diet.

They found added fat had no effect on weight, percentages of body fat, heart rate or blood pressure.

Lead researcher Professor Peter Horvath said: "The women went 1.2 to 1.5 kilometres farther before reaching exhaustion while doing very-high-speed intermittent exercise when on the high-fat diet, compared to the lower-fat diets.

Professor Horvath said that women metabolised fat more efficiently 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," he said.

"One implication of these findings is that dietary recommendations for women athletes should be different from men's."

The study involved nine female collegiate soccer players who ate three diets:

• Their normal diet
• Normal diet plus 415 calories of oil-roasted peanuts per day
• Normal diet plus an equal amount of extra calories from carbohydrate-rich energy bars.

Menstrual cycle chances

Women footballers need endurance

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 metabolise fat is greatest.

The fat content of the peanut diet was 35%, compared with 24% for the energy bar diet.

The energy bar diet was significantly higher in carbohydrates, which are traditionally thought to be the best energy source for sportspeople.

The women undertook endurance tests designed to simulate the activity associated with playing football.

The athletes were tested until exhaustion on the seventh day of each diet.

Results showed that the soccer players traveled about 15% further on the peanut diet than on a normal diet with or without energy bars, with no lessening of muscle performance.

Professor Horvath said: "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.