Heart disease and cancer are the leading killers of Americans.
But you can lower your risk by exercising and eating a mostly Mediterranean-style diet centered around plants, whole grains, lean meats, seafood and healthy fats such as olive oil.
We know this in part because of research carried out by Walter Willett, a professor and former chair of the department of nutrition at the Harvard T.H. Chan School of Public Health. Willett has published thousands of research papers and is widely considered the world’s most-cited nutritionist.
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For decades, he has led large studies that track tens of thousands of people, looking at how their diets and health behaviors influence their likelihood of developing heart disease, cancer and other conditions.
Many of Willett’s studies changed the way we eat. During the low-fat era of the 1980s and ’90s, health authorities urged Americans to eat less fat and increase the amount of carbs in their diets, saying it would lower their risk of heart disease and obesity.
But Willett argued that this advice was wrong. He and his colleagues concluded from their data that what mattered was the quality of fat and carbs, not necessarily the total amounts.
Willett warned that cutting back on fat and eating more refined carbs such as sugar, white bread, white pasta and fat-free cookies could worsen metabolic health. But eating less saturated fat from red meat, butter and fried foods and consuming more unsaturated fat from foods such as nuts, olive oil and seafood could lower heart disease risk, his studies suggested.
Willett spoke out vehemently against the low-fat dogma, including in a report he published in a medical journal in 2003 that was addressed to doctors and nutritionists. Its headline was blunt: “Stop Recommending Low-Fat Diets!“
Willett also warned that trans fats, which were found in margarine, vegetable shortenings and many packaged foods, were especially dangerous: His studies linked them to heart attacks and strokes.
Eventually, health authorities stopped recommending low-fat diets to the public, and food manufacturers were forced to remove trans fats from their products.
Born on a farm in the Midwest, Willett grew up milking cows and eating a meat-heavy diet. He studied food science and physics in college, then went on to get degrees in medicine, public health and epidemiology.
Now 81 years old, Willett is still going strong — routinely publishing papers and urging people to follow a diet that is not only good for their health but also good for the health of the planet.
Recently, I caught up with Willett to find out what he eats, how his diet has evolved over the years, and why his daily breakfast almost always includes fresh blueberries and a small glass of orange juice.
This interview has been edited for length and clarity.
What is your philosophy on nutrition?
I try to follow the best evidence on diet and health. What I eat now is very different from what I ate when I was growing up in the Midwest. Back then, we ate mashed potatoes, beef and gravy. But as the evidence came in, I shifted to a Mediterranean diet.
My one evolution occurred when I was the chair of the Eat-Lancet Commission on healthy and sustainable diets. We looked at all the data, and in the end, I realized that it came down to something pretty simple. Emphasize whole grains, fruits and vegetables, and then for major protein sources, eat about one serving of dairy and one serving of another animal source of food daily, like chicken or fish. And eat red meat no more than once per week. That’s my basic philosophy, and it’s really pretty simple to organize my day around that.
Which diet is backed by the most evidence?
There’s been a convergence. When we started our work in the 1980s, the U.S. dietary guidelines were focused on telling people that they could improve their health by avoiding fat and loading up on carbohydrates without paying attention to the type of fat or carbohydrates. But as the data from our studies came in, that’s not what we saw. It looked like total fat was irrelevant, trans fats were really bad, and saturated fats compared to refined carbohydrates were only weakly related to heart disease or mortality. But eating unsaturated fats was associated with quite substantially lower rates of heart disease and mortality.
It turns out that that fit with the traditional Mediterranean diet, which is whole grains, plenty of fruits and vegetables, olive oil and a lot of plant-based proteins such as beans, peas and lentils, with modest amounts of meat and dairy. Fish is also a regular part of the diet.
Why is the Mediterranean diet so good for health?
Willett has a fig tree in the garden at his home in Cambridge, Massachusetts. (Josh Reynolds/For The Washington Post) –
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I think it’s multiple mechanisms, not just one. Unsaturated fats have a beneficial effect on your blood lipids compared to saturated fat and refined carbohydrates. They can lower LDL cholesterol without raising triglycerides or reducing HDL cholesterol. But it’s a lot more than that. Polyunsaturated fats help reduce insulin resistance. Vegetables provide potassium, which reduces blood pressure. A number of these factors are related to lower inflammation. And the omega-3 fats in fish reduce cardiac rhythm disturbances — so things like sudden cardiac death.
What’s your typical breakfast?
I usually have steel-cut oats as a base. Then I add a cup of Greek yogurt, some nuts and fruit. I try to eat blueberries on most days as part of my fruit. In study after study, berries appear to be protective against neurodegenerative diseases like Alzheimer’s and Parkinson’s disease. It’s an area where we need more research, but berries do seem to stand out, especially blueberries.
I also have a small glass of orange juice in the morning. There are studies in multiple cohorts showing lower rates of cognitive decline when you drink orange juice on a regular basis. Orange juice does have a lot of sugar like all fruit juices do. But I only have one small glass a day.
What do you eat for lunch?
Lunch is my plant-based meal for the day. If I’m at work at the school of public health, we have a really good salad bar. So, I’ll make a big Mediterranean type of salad with fresh greens, chickpeas, nuts, hummus, tofu, and olive oil and vinegar.
When I’m at home, I don’t have time to put a lot of stuff together. When we did the Eat-Lancet Commission report, the issue of cost and convenience came up, and I said I can make a lunch for under three minutes that costs less than a dollar. It’s basically whole-grain bread with peanut butter and a little bit of jam or a touch of honey. And a carrot.
I did the calculations. It came out to 72 cents, and it takes less than three minutes. You can see a video of me preparing it on YouTube.
Is it a filling lunch?
Depending on how hungry you are, you can add another slice of bread and peanut butter. Whole-grain bread with peanut butter is quite satisfying. Today I had a variant where I added slices of avocado instead of peanut butter, and then I put olive oil and basil on top, and it was quite good.
Avocado costs a little more than peanut butter. But it still takes less than three minutes to make.
What do you eat for dinner?
My wife and I will usually have fish or poultry. Yesterday my wife made a really nice Persian dish. It was whole-grain rice with saffron, and a stew with walnuts, chicken and pomegranate. It was really good. It’s a dish that I had in Tehran when I was first there.
When we want something quick, we might bake some fish with olive oil, and we’ll have it with cooked greens or veggies.
If I’m by myself, I will usually make a salad. The quickest thing for me is to go to Trader Joe’s and get their washed spring greens. I’ll add some olives and fresh vegetables. And often I’ll get a tin of oysters or mussels and put that on the salad. I can make that in under five minutes. Oysters and mussels are very nutritious, and they’re sustainable.
Do you ever snack?
I always try to have apples and carrots on hand. When I was writing a textbook some years ago, I always wanted something to chew on. But I wasn’t careful and I gained five pounds because I was snacking on cookies and chips. I didn’t want that to happen again. So, for the next edition of the book, I made sure to have apples and carrots on hand — and I didn’t gain any weight. So that’s now my go-to snack. They’re low in calories and very satisfying.
What do you do for exercise?
I ride my bike to work. It’s the quickest and most reliable way to get to work. I also try to do things like sit-ups, resistance bands and resistance work.
What’s your advice for our readers?
Willett recommends leaning into a plant-heavy diet, with about a serving of dairy and a serving of animal protein, such as chicken or fish, per day. (Josh Reynolds/For The Washington Post) –
If I could put 40 years of research into one answer, it would be to eat a variety of healthy, mostly plant-based foods, and find a way to do it that’s enjoyable.
Do you have a question about healthy eating? Email EatingLab@washpost.com and we may answer your question in a future column.