Low-Fat Diet Doesn't Lower Your Risk for Heart Disease

The largest study ever to ask whether a low-fat diet reduces the risk of getting cancer or heart disease has found that the diet has 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 attacks and strokes as those who ate whatever they pleased, researchers reported recently. "These studies are revolutionary," said Dr. Jules Hirsch, physician in chief emeritus at Rockefeller University in New York City, who has spent a lifetime studying the effects of diets on weight and health. "They should put a stop to this era of thinking that we have all the information we need to change the whole national diet and make everybody healthy."

The study, published in the Journal of the American Medical Association recently, was not just an ordinary study, said Dr. Michael Thun, who directs epidemiological research for the American Cancer Society. It was so large and so expensive, Thun said, that it was "the Rolls-Royce of studies." As such, he added, it is likely to be the final word.

"We usually have only one shot at a very large-scale trial on a particular issue," he said.

The study was part of the Women's Health Initiative of the National Institutes of Health, the program that showed that hormone therapy after menopause might have more risks than benefits.

The results, the study investigators agreed, do not justify recommending low-fat diets to the public to reduce their heart disease and cancer risk. The investigators added that the best dietary advice was to follow federal guidelines for healthy eating less saturated fats and trans fats, more grains and more fruits and vegetables.

Not everyone was convinced. Some, like Dr. Dean Ornish, a promoter of low-fat diets and president of the Preventive Medicine Research Institute in Sausalito, Calif., said the women did not reduce their fat to low enough levels or eat enough fruits and vegetables. He also said the study, even at eight years, did not give the diets enough time.

Others said diet could still make a difference, at least with heart disease, if people were to eat the Mediterranean diet, which is low in saturated fats, like butter, and high in oils, like olive oil. The women in the study reduced all kinds of fat.

The diets studied "had an antique patina," said Dr. Peter Libby, a cardiologist and professor at Harvard Medical School. These days, Libby said, most people have moved on from the idea of controlling total fat to the idea that people should eat different kinds of fat.

But the Mediterranean diet has not been subjected to a study of this scope, researchers said.

Barbara Howard, an epidemiologist at MedStar Research Institute, a nonprofit hospital group, and a principal investigator in the study, said people should realize that diet alone was not enough to stay healthy.

"We are not going to reverse any of the chronic diseases in this country by changing the composition of the diet," Howard said. "People are always thinking it's what they ate. They are not looking at how much they ate or that they smoke or that they are sedentary."