The Best Diet: Eat Like Our Ancestors
Is BMI the best way to gauge your health?
It's not at all the best measurement, but some of the really best research studies use BMI as an outcome. Waist/hip ratio, waist/height ratio, waist measurements—those all correlate rather well with body fat percentage, which is what you really want to know. But that is very hard to measure accurately. As far as BMI goes, for most of us, it will correlate pretty well. If you're at the low end of the normal BMI range, you're not going to have a frightening amount of body fat.
So how do we address being overweight? Don't we have to find the emotional reason behind why we binge?
There's an indirect interaction between having some kind of psychological problem and overeating. It's absolutely harder to lose weight if you're depressed or anxious or have post-traumatic stress syndrome. I don't mean that those conditions won't aggravate the problem. But it's not the original, basic cause of most overeating. And, like smoking, you can change the habit before you fix emotional problems.
You say that eating healthfully is largely a matter of habit.
We get into routines. Brain imaging has shown that if you have no routine and are trying to change—say you're in the cafeteria line thinking, "There's the ice cream; do I want to stick to my diet today?"—the prefrontal cortex, the area of the brain involved with complex thought, is active. If you're in a real routine, whether it's a bad one or a good one, the lower basal ganglia—the older part of the brain that isn't associated with conscious thought—is active. The upper advanced brain can be thinking about something else. So if you always order the salad and the bowl of berries, you don't even think about the banana split.
It takes willpower to change those habits.
People like to say that willpower is either a myth—it doesn't exist—or that dieting has nothing to do with willpower. All willpower means is resolutely following through on decisions without getting derailed by short-term temptations. It's very straightforward. The most generous interpretation of why willpower gets bad press as a diet technique is that lots of people have so little of it. But it's a trainable skill.
If most of us could change our bad eating habits through willpower, why do you also offer up public policy prescriptions, such as banning trans fats or taxing unhealthy foods?
In the long term, society has to change. There is no one root of the problem. We've got to change the current food and nonexercise environment if you're talking about getting the population as a whole back to fitness. But most people today want to fix their own health somewhat faster than the rest of the world is changing. So in the longer term, and on a wider scale, I advocate things ranging from outlawing certain things—like advertising junk food to kids—to changing financial incentives so that, say, agricultural subsidies are shifted to healthier foods.
And if I want to start with myself, what should I eat?
We should try to eat as much like our ancestors as possible, with those proportions of protein and fiber. When you look at them, all the standard diets are essentially converging. If you read the last Atkins book, he talks about eating fish, not a ton of saturated fat. And [low-fat guru] Dean Ornish says you should be eating whole-grain carbohydrates, not simple carbs like white bread. Basically, it's fish and lean meats, lots of fruit and veggies, and lots of fiber. And exercise is essential.
Are you optimistic we'll change our ways?
The outlook is quite good for an individual who is very committed to change. In terms of larger society or the world, I'm optimistic in the long run and pessimistic in the short run. Things will get worse before they hit a turning point. At some point it will be clear that our habits are killing us, and that will finally lead to radical change. I'd just like to see that happen sooner rather than later. We waited so long on smoking.