Starting a low-fat diet in mid-life does not, by itself, decrease a woman’s risk of heart disease or stroke or dramatically reduce her risk of breast or colorectal cancer, according to three studies published today of almost 50,000 healthy, post-menopausal women. But don’t break out the ice cream just yet. Once you get into the nitty gritty of the study, the investigators stress, the findings still support the general idea that you need to pay attention to how much fat — and particularly what kinds of fat — you eat.
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By GINA KOLATA
Published: February 7, 2006

The largest study ever to ask whether a low-fat diet keeps women from getting cancer or heart disease has found that the diet had no effect.

The $415 million federal study involved nearly 49,000 women aged 50 to 79 who were followed for eight years. In the end, those assigned to a low-fat diet had the same rates of breast cancer, colon cancer, and heart attacks and strokes as those who ate whatever they pleased, researchers are reporting today.

Those who ate the higher-fat diets also had no more diabetes, no higher blood glucose or insulin levels, no higher blood pressure. And the different diets did not make much difference in anyone’s weight. By the end of the study, women in the two groups weighed about the same. But women in the low-fat group had slightly lower levels of low density lipoprotein cholesterol, or LDL, which increases heart disease risk.

The results should put an end to more than two decades of speculating that a low-fat diet is protective, said Dr. Michael Thun, who directs epidemiological research for the American Cancer Society. The new study, he said, “was the Rolls Royce of studies that would answer this question.”

Considering the time, effort, and money it takes to do such a study, Dr. Thun and others added, it is unlikely that anything like it will ever be attempted again. “We usually have only one shot at a very large-scale trial on a particular issue,” Dr. Thun said.
Study Finds Low-Fat Diet Won’t Stop Cancer or Heart Disease - New York Times