Dr. Walter Willett on Living Healthier

Dr. Walter Willett, M.D., is considered a pioneer in researching the link between nutrition and health. He’s a professor of epidemiology and nutrition and chairman of the Department of Nutrition at Harvard School of Public Health, one of the principal investigators for The Nurses’ Health Study II and one of the most cited nutritionists in the world. His book, Eat, Drink, and Be Healthy: The Harvard Medical School Guide to Healthy Eating, continues to be a bestseller more than seven years after publication. He’s a member of the Institute of Medicine of the National Academies and the recipient of many national and international awards for his research. In this interview, Willett explains why the Western diet is so unhealthy.

How would you define health?

It’s, in general, what the World Health Organization considers health to be, meaning not just the absence of disease, but a state of well-being and mental well-being. To a certain degree, we’re architects of our own health: We have no guarantee for mortality or immortality, but we can very dramatically improve our chances of staying well by having a healthy diet and lifestyle. It’s not just preventing a hypothetical heart attack or cancer down the road, it’s feeling better on a day-to-day basis.

How did you get started in this field?

I became interested in this area in the late 1970s, specifically when people were really being told, “Eat this and don’t eat that.” When I scratched the surface, looking for the evidence for these edicts, there wasn’t really much. It was based—most of the time—on the best guesses of very indirect evidence. We now have more than 250,000 men and women for whom we’ve collected dietary data for up to 25 years.

What makes the American diet so lethal?

Well, many different aspects of diet are important, not just one single factor. The first one is simply too many calories in relation to our level of physical activity, and that leads to weight gain. Being overweight is the single most important nutritional problem in our country. We consume large amounts of animal fats that we now recognize are not healthy. Another problem is trans-fat intake, which comes from partially hydrogenated vegetable oils. We’ve come to appreciate that un-hydrogenated, unsaturated fats actually have positive health benefits. We’re better off having more of those than the unhealthy fats. We’ve also come to realize that large amounts of refined starches and sugar in the American diet are not good for cardiovascular disease, diabetes and some cancers. Unfortunately, these foods comprise the majority of the U.S. diet and are really not good for us.

Why do Americans have such an unhealthy diet?

Part of the answer is that refined starches, sugars and hydrogenated oils are very inexpensive forms of food and the basic ingredients cost very little to produce. Companies can make them into many different types of products and sell them for a lot of money. And those are, of course, heavily marketed. We would be better off consuming more fruits and vegetables, but that’s not as important as avoiding some of these other things.

Are diseases like stroke and diabetes genetic or environmental?

What we’ve known for a long time is that the major determinates of the most important diseases in this country, such as most cancers, cardiovascular disease, stroke and diabetes, are not genetic factors, but diet and lifestyle factors. We’ve known it for many years because we’ve learned that people in other countries, say Africa and parts of Asia and Latin America, often have extremely low rates of the diseases that are major causes of death in this country. When these people migrate to the United States, they get virtually the same rates that most people in this country are experiencing.

Do genes play a role in which diseases people get?

There are clearly different systems and genetic responses, but what we’ve seen is even if someone has a strong family history of diabetes and heart disease, they can still be at very low risk for those conditions. Diet and lifestyle factors will override most genetic predispositions, except for extremely strong predispositions.

Is there a fast path to healing?

Well, it depends on what’s ailing you in the first place, so there’s no simple answer to that. The majority of the U.S. population is eating poorly; the failure of nutrition is remarkable. Two thirds of the population is technically overweight or obese and a higher percentage is above their optimal weight. I published a book a couple of years ago, Eat, Drink and Be Healthy, that was written from the standpoint of preventing heart disease, cancer and other chronic conditions over the long run. I got flooded with emails from people saying, “Thank you! You’ve changed my life. I thought I was eating right, but I realized I wasn’t after reading your book. After a couple of months, I’ve lost weight, my cholesterol levels are better and my glucose is under control. I feel better and I have more energy.” When people start making changes, the benefits begin paying off in a matter of a few months.

How do you view traditional medicine versus alternative medicine?

Nutrition should be the base of both modern and traditional medicine. Unfortunately, in American medicine, diet and lifestyle often get a very casual mention and there’s a quick leap to write expensive prescriptions for expensive drugs. You have to realize that physicians don’t get compensated for dietary counseling. It takes time and knowledge that most of them don’t have. And sometimes patients just want a quick fix.

We’re missing a huge opportunity for improving the quality of life and making medical care more effective and less costly. We’ve been able to document that unhealthy diet and lifestyle accounts for more than 80% of heart disease, 90% of type 2 diabetes, 70% of stroke and colon cancer and high percentages of other conditions, as well. So, the dominant causes of major diseases are diet and lifestyle. That would include, of course, smoking, low activity levels and being overweight.

For more information on Dr. Walter Willett, visit www.hsph.harvard.edu.

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About Dr. Walter Willett