Tuesday, February 07, 2006

Bring On the Brownies and Pasta

A major new federally funded study conducted on 49,000 middle-aged to elderly women has found that a low-fat diet does not have a protective effect against heart disease, stroke, or cancer, as doctors and medical researchers have been telling us it does for decades.

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 heart attack and stroke as those who ate whatever they pleased, researchers are reporting today.

"These are three totally negative studies," said Dr. David Freedman, a statistician at the University of California at Berkeley, who is not connected with the study but has written books on clinical trial design and analysis. And, he said, the results should be taken seriously for what they are -- a rigorous attempt that failed to confirm a popular hypothesis that a low-fat diet can prevent three major diseases in women.

And the studies were so large and so expensive that they are "the Rolls Royce of studies," said Dr. Michael Thun, who directs epidemiological research for the American Cancer Society. As such, he said, they are likely to be the final word.
...For decades, many scientists have been saying, and many members of the public have been believing, that what you eat -- the composition of the diet -- determines how likely you are to get a chronic disease. But it has been hard to prove. Studies of dietary fiber and colon cancer failed to find that fiber was protective. Studies of vitamins thought to protect against cancer failed to show an effect.

Gradually, many cancer researchers began questioning the dietary fat-cancer hypothesis, but it has retained a hold on the public imagination.

"Nothing fascinates the American public so much as the notion that what you eat rather than how much you eat affects your health," said Dr. Peter Libby, a cardiologist and professor at Harvard Medical School.

But the new studies, reported in the Feb. 8 issue of the Journal of the American Medical Association, found that women who were randomly assigned to follow a low-fat diet ate significantly less fat over the next eight years. But they had just as much breast and colon cancer and just as much heart disease.

And, confounding many popular notions about fat in the diet, the different diets did not make much difference in anyone's weight. The common belief that carbohydrates in the diet lead to higher insulin levels, higher blood glucose levels and more diabetes was also not confirmed. There was no such effect among the women eating low-fat diets.

One more diet industry sacred cow into the dustbin of history, where it can join the belief that thin people live longer than fat people.

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