NCPA - National Center for Policy Analysis


February 8, 2006

If you're a postmenopausal woman, simply trimming the fat from your diet isn't enough to protect against heart disease or breast or colorectal cancer, a government-sponsored study of nearly 50,000 women reports.

The new findings, published in the Journal of the American Medical Association, come from the landmark Women's Health Initiative. The initiative is best known for showing that postmenopausal hormones do not protect against heart attack and stroke.

In addition to the hormone studies, the health initiative also randomly assigned 48,835 postmenopausal women ages 50 to 79 to one of two diet groups. About 60 percent were told to continue eating what they wanted. The rest were asked to cut fat intake to 20 percent of total calories, eat at least five servings of fruits and vegetables -- the very minimum set by current government guidelines -- and eat six servings of grains a day. The women were followed for an average of eight years.

  • Over the course of the study, women in the low-fat group on average reduced their fat intake from about 38 percent of calories to about 29 percent.
  • They lost only a pound more than the woman who followed their usual diet, probably because they replaced high-fat foods with lower-fat, simple carbohydrates that contained just as many calories, says Stanford University's Marcia Stefanick, chairwoman of the Women's Health Initiative's steering committee.

Waiting until midlife to cut the fat might be too late as far as cancer risk, says Jacques Rossouw of the National Heart, Lung and Blood Institute and Women's Health Initiative project officer. The hypothesis that a low-fat diet reduces cancer risk arose from studies of countries in which people ate relatively little fat their entire lives, he says.

Source: Rita Rubin, "Cutting fat alone isn't enough, women advised," USA Today, February 8, 2006; and Ross L. Prentice et al., "Low-Fat Dietary Pattern and Risk of Invasive Breast Cancer: The Women's Health Initiative Randomized Controlled Dietary Modification Trial," Journal of the American Medical Association, Vol. 295 No. 6, February 8, 2006.

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