More Fiber, Less Fat Help Prevent Ovarian Cancer

According to Prentice, the diet was developed especially for this research and doesn't follow any contemporary "popular" diets.

"In particular, the Women's Health Initiative intervention did not have a goal of restricting energy [calorie] consumption, though participating intervention group women did lose some weight. Nor was there an attempt to reduce carbohydrates," said Prentice. "On the contrary, most of the reduced dietary fat was replaced by complex carbohydrates."

The potential link between dietary fat and cancer is not fully understood, he added. During the study, Prentice said the researchers did note lower levels of estradiol -- an estrogen hormone produced by the ovaries -- in the blood of dieting women. Estradiol is an important risk factor for cancer among women, he said.

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"This or other circulating hormones could have a stimulatory effect on epithelial [blood vessel] tissue in the ovary or breast, possibly including effects on cells in yet undiagnosed cancers," Prentice explained.

"The evidence for reductions in ovarian and breast cancer is strongest among women whose usual [prior] diet was relatively high in fat (e.g. more than 35 percent of calories) who made a comparatively large fat reduction if assigned to the low-fat diet group," he added.

There is an increasing amount of evidence linking healthier diets and exercise to lower cancer risk. But Prentice said he would like to see more basic-science research focused on the ways in which these lifestyle changes affect the biochemical mechanisms that drive cancer.

More information

For more about the USDA's dietary guidelines, visit MyPyramid.