NY Times: Low-Fat Diet Does Not Cut Health Risks, Study Finds

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Low-Fat Diet Does Not Cut Health Risks, Study Finds

By GINA KOLATA

A large study has found that a low-fat diet has no effect

in reducing the risk of getting cancer or heart disease.

http://www.nytimes.com/2006/02/08/health/08fat.html?th & emc=th

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 ages 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

are reporting today.

" 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 today's issue of The Journal of the American

Medical Association, was not just an ordinary study, said Dr.

Thun, who directs epidemiological research for the American Cancer

Society. It was so large and so expensive, Dr. 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 results, the study investigators agreed, do not justify

recommending low-fat diets to the public to reduce their heart disease

and cancer risk. Given the lack of benefit found in the study, many

medical researchers said that the best dietary advice, for now, was to

follow federal guidelines for healthy eating, with less saturated and

trans fats, more grains, and more fruits and vegetables.

Not everyone was convinced. Some, like Dr. Dean Ornish, a longtime

promoter of low-fat diets and president of the Preventive Medicine

Research Institute in Sausalito, Calif., said that the women did not

reduce their fat to low enough levels or eat enough fruits and

vegetables, and that the study, even at eight years, did not give the

diets enough time.

Others said that diet could still make a difference, at least with

heart disease, if people were to eat the so-called Mediterranean diet,

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. Libby, a

cardiologist and professor at Harvard Medical School. These days, Dr.

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.

And Barbara V. , an epidemiologist at MedStar Research Institute,

a nonprofit hospital group, and a principle 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, " Dr. 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. "

Except for not smoking, the advice for a healthy lifestyle is based

largely on indirect evidence, Dr. said, but most medical

researchers agree that it makes sense to eat well, control weight and

get regular exercise.

That is also what the cancer society recommends. Dr. Thun, who

described the study's results as " completely null over the eight-year

follow-up for both cancers and heart disease, " said his group had no

plans to suggest that low-fat diets were going to protect against

cancer.

Others cautioned against being too certain that a particular diet would

markedly improve health, and said that whether someone developed a

chronic disease might not be entirely under their control — genetics

also plays a role.

A. Freedman, a statistician at the University of California,

Berkeley, who is not connected with the study but has written books on

the design and analysis of clinical trials, said the results should be

taken seriously.

" The studies were well designed, " Dr. Freedman said, " and the

investigators tried to confirm popular hypotheses about the protective

effect of diet against three major diseases in women. "

" But, " he added, " the diet studied here turned out not to be protective

after all. "

The study was part of the Women's Health Initiative of the National

Institutes of Health, the same program that showed that hormone therapy

after menopause might have more risks than benefits.

In this case, the study addressed a tricky problem. For decades, many

scientists have said, and many members of the public have believed,

that what people eat — the composition of the diet — determines how

likely they are to get a chronic disease. But that has been hard to

prove. Studies of dietary fiber and colon cancer failed to find that

fiber was protective, and studies of vitamins thought to protect

against cancer failed to show an effect.

Many cancer researchers have questioned large parts of the diet-cancer

hypothesis, but it has kept 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. Libby, the

Harvard professor.

The study 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. The women were not trying to lose weight, and their weights

remained fairly steady. But their experiences with the diets allowed

researchers to question some popular notions about diet and obesity.

There is a common belief that Americans get fat because they eat too

many carbohydrates. The idea is that a high-carbohydrate, low-fat diet

leads to weight gain, higher insulin and blood glucose levels, and more

diabetes, even if the calories are the same as in a higher-fat diet.

That did not happen here.

Others have said the opposite: that low-fat diets enable people to lose

weight naturally. But that belief was not supported by this study.

As for heart disease risk factors, the only one affected was LDL

cholesterol, which increases heart disease risk. The levels were

slightly higher in women eating the higher-fat diet, but not high

enough to make a noticeable difference in their risk of heart disease.

Although all the study participants were women, the colon cancer and

heart disease results should also apply to men, said Dr. Jacques

Rossouw, the project officer for the Women's Health Initiative.

Dr. Rossouw said the observational studies that led to the hypothesis

about colon cancer and dietary fat included men and women. With heart

disease, he said, researchers have found that women and men respond in

the same way to dietary fat.

The most recent study follows a smaller one, reported last year, on

low-fat diets for women who had breast cancer. That study hinted that

eating less fat might help prevent a recurrence. But the current study,

asking if a low-fat diet could protect women from breast cancer in the

first place, had findings that fell short of statistical significance,

meaning they could have occurred by chance.

Dr. Rossouw said he was still intrigued by the breast cancer data, even

though it was not statistically significant. The women on low-fat diets

had a 9 percent lower rate of breast cancer; the incidence was 42 per

thousand per year in women in the low-fat diet group, compared with 45

per thousand per year in women consuming their regular diet.

That could mean that fat in the diet may have a small effect, Dr.

Rossouw said, perhaps in some subgroups of women or over a longer

period of time. He added that the study investigators would continue to

follow the women to see if the effect became more pronounced.

While cancer researchers said they were disappointed by the results,

heart disease researchers said they were not surprised that simply

reducing total fat had no effect, because they had moved on from that

hypothesis.

Of course, Dr. Libby acknowledged, the latest advice, to follow a

Mediterranean diet and get regular exercise, has never been tested in a

large randomized clinical trial. " If they did a study like that and it

was negative, " he said, " then I'd have to give up my cherished

hypotheses for data. "

The low-fat diet was not easy to follow, said Dr. Rowan T. Chlebowski,

a medical oncologist at Harbor-U.C.L.A. Medical Center and one of the

study's principal investigators. Women were told to aim for a diet that

had just 20 percent of its calories as fat, and most fell short.

The diet they were told to follow " is different than the way most

people eat, " Dr. Chlebowski said. It meant, for example, no butter on

bread, no cream cheese on bagels, no oil in salad dressings.

" If a physician told a patient to eat less fat, that will do nothing, "

he said. " If you send someone to a dietitian one time, that will do

next to nothing. " The women in the study had 18 sessions in small

groups with a trained nutritionist in the first year and four sessions

a year after that.

In the first year, the women on the low-fat diets reduced the

percentage of fat in their diet to 24 percent of daily calories, and by

the end of the study their diets had 29 percent of their calories as

fat. In the first year, the women in the control group were eating 35

percent of their calories as fat, and by the end of the study their

dietary fat content was 37 percent. The two groups consumed about the

same number of calories.

Some medical specialists emphasized that the study did not mean people

should abandon low-fat diets.

" What we are saying is that a modest reduction of fat and a

substitution with fruits and vegetables did not do anything for heart

disease and stroke or breast cancer or colorectal cancer, " said Dr.

Nanette K. Wenger, a cardiologist and professor of medicine at Emory

University School of Medicine in Atlanta. " It doesn't say that this

diet is not beneficial. "

But Dr. Freedman, the Berkeley statistician, said the overall lesson

was clear.

" We, in the scientific community, often give strong advice based on

flimsy evidence, " he said. " That's why we have to do experiments. "

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