Facing the fat - and the facts

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Facing the fat - and the facts

Early in 2006, the publication of three major reports from the Women's Health Initiative (WHI) caused quite a stir. They showed clearly that modest reductions in total dietary fat over an eight-year period do not lower the risk of coronary artery disease, breast cancer, or colon cancer in postmenopausal American women.

It's understandable that these findings were greeted with disappointment, confusion, and frustration. Many interpreted the results to mean that dietary fat does not influence health — or that nutrition itself is unimportant. Now that the furor has settled down and several months have passed, we can view the results in perspective.

Men may be tempted to dismiss the WHI results simply because the genders are different. Indeed, heart disease is different in men, occurring about 10 years earlier, sometimes producing different types of blockages, and often producing different symptoms. Colon cancer affects both genders equally, but breast cancer does not. And men have the unique worry of prostate cancer, a disease that's been linked to dietary fat. For instance, in the early 1990s, when the WHI was getting started, Harvard's Health Professionals Follow-Up Study reported that men who eat large amounts of fat are 1.79 times more likely to develop advanced prostate cancer than men who eat less fat. In this study, as in others, saturated fat from animal sources was the chief culprit.

Men may rightly feel that the WHI findings don't apply to them — but they should also understand why the results should not tempt either men or women to favor fatty foods.

The WHI results surprised few experts in nutrition. The trials were launched in 1993, when scientists still believed that all fats were created equal and that all were equally harmful. Since then, abundant data have accumulated to show that some fats (saturated fat and trans-fatty acids) are indeed harmful, but that others (omega-3 and mono-unsaturated fatty acids) appear protective. The WHI targeted only total fat consumption without distinguishing "bad" fats from "good" fats.

Even more important, nutritional science has moved from considering dietary fat in isolation to viewing it as one component in the overall diet. Just as there are good fats and bad, we've learned that there are good carbs (dietary fiber and other complex carbohydrates) and bad (simple sugars and other rapidly absorbed carbohydrates). We've learned that calories do count, and that salt does, too. And since people eat foods, not nutrients, we've learned that fish, nuts, whole grains, vegetables, and fruit all contribute to a healthful dietary pattern.

The WHI dietary intervention failed to account for any of this information. The study diet was high in carbohydrates (54 grams a day) but low in fiber (17 grams). That means the women compensated for their modest reductions in dietary fat by increasing their consumption of simple carbohydrates. They did not reduce their caloric intake, and they did not lose weight.

America is in the midst of a worrisome epidemic of obesity (see figure); diabetes and cardiovascular disease are among its consequences. There is a reason for these woes — two reasons, actually. The first is diet. Americans eat too few healthful foods and too many harmful ones. In fact, we eat way too much: Between 1971 and 2000, the average man added 168 calories to his daily fare, while the average woman added 335 calories a day.

Trends in adult weight Percent of adults ages 20–74* who were at a healthy weight, overweight, or obese† *Data are age-adjusted to the 2000 U.S. standard population. †Healthy weight, body mass index (BMI) = 18.5–24; overweight, BMI = 25–29; obese, BMI = >30. Sources: National Health and Nutrition Examination Survey (National Center for Health Statistics); Cancer Trends Progress Report — 2005 Update (National Cancer Institute 2005).

The second reason for our predicament is inadequate exercise. According to a 2004 study, the average American adult spends 170 minutes a day watching television but only 19 minutes in physically active tasks. Fewer than 25% of us get enough exercise. "Spectator" is a kind word for it. In fact, we are a nation, and increasingly a world, of couch potatoes.

The WHI studies show that it is difficult to achieve dietary change. The investigators aimed for a diet providing 20% of its calories from fat; instead, they got 24% at the start of the trial and 29% at the end. One reason may have been the punitive, "thou shall not eat" approach to dietary advice. Instead, we should encourage experimentation with healthful foods that can be interesting and enjoyable as well as beneficial.

There are also many barriers to getting enough exercise. The conveniences of the information age, the allure of passive entertainment, and pervasive cultural norms all contribute. Unfortunately, physicians have unwittingly erected additional barriers. Exercise guidelines are confusing at best; for example, the Surgeon General calls for 30 minutes a day, the Institute of Medicine, 60 minutes, and the 2005 Dietary Guidelines for Americans, 30–90 minutes. And the legacy of the aerobics doctrine is even harder to overcome. By showing that intense exercise is essential for optimal fitness, it made exercise intimidating and difficult. Scientists have learned that although aerobic-intensity workouts are best for fitness, moderate exercise is excellent for health — but the lingering refrain "no pain, no gain" deters many from enjoying the benefits of moderate activity.

As a group, the WHI volunteers were overweight and inactive. It would be hard for even the best diet to overcome these impediments to health, so it's not surprising that a simple, modest reduction in total fat failed to make a difference.

True, more study is needed to determine just what diet is best. It's complex, expensive research, and it's slow. But while we are waiting for science to find the critical pieces in the jigsaw puzzle of health, we'd all be wise to follow the outlines that are well established. They include a sound diet, sufficient exercise, no tobacco, moderate alcohol use, and a balance between stimulation and relaxation. This healthful lifestyle will be easier to achieve if we see it as an opportunity, not a punishment.

In due time, it's likely that science will confirm the 2,400-year-old wisdom of Hippocrates: "If we could give every individual the right amount of nourishment and exercise, not too little and not too much, we would have found the safest way to health."

Last updated:	September 05, 2008