Set the record straight on low-fat diets.

Byline: Dean Ornish

Counseling and motivating our patients to change their diet and lifestyle is tough enough, but the results from the Women’s Health Initiative’s examination of low-fat diets are likely to make that job even harder.

The study results, which were reported in three papers published in the Feb. 8 issue of the Journal of the American Medical Association, made headlines around the world. I’m concerned that the way this study was reported may cause many of our patients to throw up their hands and wonder why they are trying so hard to adhere to a way of eating that science says holds no benefit.

Having seen what a powerful difference changes in diet and lifestyle can make, it concerns me that the Women’s Health Initiative study may discourage many people from making changes that can be so beneficial to them. That’s why it’s critically important to understand the limitations of this study and continue to advise our patients about the benefits of low-fat, whole foods nutrition.

The Women’s Health Initiative (WHI) study examined the rates of colorectal cancer, heart disease, and stroke in women who followed a low-fat diet, compared with women with normal diets. The researchers reported no statistically significant reductions in any of the diseases.

The study is seriously flawed. If you don’t change much, you don’t improve much. Given how small the changes in diet were, it’s not surprising that there were few effects. Even if a study of a diet has 49,000 women and spends $450 million, it’s not going to show very much if people don’t follow the diet. And it’s not going to show very much if both groups changed their diet to about the same extent. That’s what happened.

The women in the study were asked to reduce their dietary fat to 20% of calories, but they reported reducing it only to 29%. It’s unlikely they even did that well, since they reported reducing their caloric intake from 1,700 to 1,500 calories/day, but they didn’t lose weight. It’s very common for people to report that they’re following a diet better than they really are. LDL cholesterol levels decreased only 2.6% more in the low-fat diet group than in the comparison group, hardly any difference at all. Blood pressure decreased hardly at all in either group, only about 2% in both groups.

By analogy, it’s as though the women in one group reduced the number of cigarettes they smoked each day from 60 to 57 and in the other group from 60 to 55. You wouldn’t expect to see much difference in the rates of lung cancer in these two groups. In other words, they didn’t test the hypothesis.

In contrast, the subgroup of women who started with the highest consumption of dietary fat and made the biggest reductions did show a significant reduction in their risk of breast cancer. Also, the risk of myocardial infarction was lower in the subgroup of patients who had the greatest reduction in fat intake and the greatest increase in consumption of fruits and vegetables.

In addition, the WHI study focused on a total reduction in fats, but did not draw any distinctions between “good fats” (such as omega-3 fatty acids) and “bad fats” (such as saturated fat and trans fats). The participants in the low-fat arm of the study also did not increase their consumption of fruits and vegetables very much.

Other studies using serial coronary arteriography have shown that a 30% fat diet is not enough to stop the worsening of coronary artery disease in most people. For almost 30 years, my colleagues and I at the nonprofit Preventive Medicine Research Institute and the University of California, San Francisco have conducted randomized controlled trials showing that more intensive changes in diet and lifestyle may stop or reverse the progression of coronary heart disease in most patients, without drugs or surgery. These include a diet much lower in saturated fat and trans fatty acids and high in fruits, vegetables, whole grains, legumes, and soy products, along with moderate exercise, stress management techniques (such as yoga and meditation), and support groups.

These studies used the latest in high-tech, state-of-the-art measures (such as quantitative coronary arteriography and cardiac PET scans) to prove the power of simple, low-cost, and low-tech lifestyle changes. The frequency of angina decreased by more than 90% in the first few weeks, and most people became pain-free. We measured improved myocardial perfusion in only 1 month. After 1 year, even severe coronary atherosclerosis improved. There was even more reversal after 5 years than after 1 year.

And there were 2.5 times fewer cardiac events in the group that made comprehensive lifestyle changes, compared with a randomized control group of patients who made changes similar to those in the Women’s Health Initiative.

We recently published the first randomized controlled trial showing that these intensive changes in diet and lifestyle may stop or even reverse the progression of prostate cancer in men.

In both heart disease and prostate cancer, we found that the more people changed their diet and lifestyle, the more improvement we measured. In order to reverse disease, people needed to make much bigger changes than most doctors had been recommending. If you can reverse disease, then it’s even easier to prevent it.

If patients are trying to lower LDL cholesterol, they can begin by making moderate changes in diet and lifestyle, for example, a Step 1 diet or Adult Treatment Panel III diet. If that lowers LDL cholesterol sufficiently, great; if not, they can make bigger changes rather than being told that they “failed diet.” In our studies, patients showed a 40% average reduction in LDL cholesterol after 1 year without lipid-lowering drugs.

It’s not just “low fat.” An optimal diet is low in bad fats and higher in good ones; low in refined carbohydrates and high in unrefined ones; low in red meat and high in fruits and vegetables. To the degree they move in a healthful direction on the spectrum, they are likely to look better, feel better, lose weight, and gain health.

DR. ORNISH is president of the nonprofit Preventive Medicine Research Institute and clinical professor of medicine at the University of California, San Francisco.