CHICAGO -- A big study offers somewhat conflicting results for diets that cut fat and raise carbohydrates.

The lead author said the study, published in Wednesday's issue of the Journal of the American Medical Association, refutes claims that low-fat diets help cause obesity. However, it doesn't lead to significant weight loss, either.

The national study examined the different health benefits of a low-fat diet that includes carbohydrates. The study is still going on, but after seven years, researchers have enough data to announce the results.

"Our study shows that increasing carbohydrates as we did it, with an emphasis on vegetables and fruits and grains, in fact does not promote weight gain," said Dr. Barbara Howard, of the MedStar Research Institute in Washington, D.C.

Howard and colleagues from across the country studied more than 48,000 postmenopausal women, some of whom went on low-fat diets. Almost half the women in the study cut back on high-fat food and replaced it with carbs from fruits, whole grains and vegetables.

The study was not meant to measure weight loss, but to find out if a low-fat diet has other health benefits. However, researchers decided to measure the impact on weight as well.

"The ones who were counseled to follow a lower-fat eating pattern with more vegetables, fruits and grains lost some weight at first -- about 5 pounds -- and their weight all through the seven years was less than the women who didn't follow this pattern," said Howard.

He said the diet did not cause weight gain in any women in the study, whether they were black, white, Hispanic, diabetic, at a healthy weight or obese.

In all, the study found older women who ate less fat and more carbohydrates lost about two pounds over seven years.

An obesity expert at Tufts-New England Medical Center said that skimpy weight loss will disappoint people seeking an obesity cure. Dr. Michael Dansinger said it's "like losing the Super Bowl but claiming a second-place victory."

But the women in the study were not trying to lose weight. If they were, they would have needed to cut calories and exercise more. But this study shows that eating the right kind of carbs will not cause weight gain.

Dr. Barry Sears, the author of "The Zone" diet, said he still believes low-fat, high-carb diets cause weight gain. He said women on the diet lost only a fraction of a pound a year while increasing waist size.

Some of the study participants who shed pounds during the study maintained their weight afterwards by using what they learned on the low-fat diet.

"Fried was a curse word," said Frances Plummer, who took part in the study. "We were not allowed to have fried foods. The F-word. So now I am able to forgo fried foods in many instances."

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