The Skinny on Getting Thin

Despite all the evidence that diets don't work, why do people keep trying?
We live in a society where thin—and thinner and thinner—is a beauty standard. People are judged by how fat they are. It would be ridiculous to tell people, "Don't even try."  You can't tell people, "Just embrace your fatness." There are people who do that, but it's very, very hard. But I would say, when you get to a point where you cannot hold that weight any more, that's probably the best you can do. There's nothing wrong with you personally. You probably will have to think about keeping yourself at the bottom of your weight range.

You're slim, and you're a runner. Can you jog to stay slim and not diet?
I love running. I don't know how much thinner it really makes people. My son ran the Boston Marathon in two hours and 35 minutes. When he started training for the Boston Marathon, he was running 30 miles a week. He upped it to 100 miles a week. He only lost three pounds. I don't know of any study where people lost weight from exercise alone. Your brain has you eating enough to make up for it.

Why does every diet seem to reach a plateau where weight-loss stops?
You've gotten to the lowest you're going to get, the lowest your body wants you to get to, and your metabolism slows down. The same amount of food that used to be OK for you is now making you gain weight.

Americans are fatter than ever, which would seem to indicate that something about the modern environment—not just genes—is causing obesity, right?
It's really hard to know what's caused it. Maybe serving sizes are bigger? But are serving sizes bigger because people need more food now because they're bigger and fatter? The industry really does respond to consumer demand. Things are bigger. We just got some new silverware. I said, "Look at this—the forks and everything have gotten bigger." Do people want more food now because their bodies are bigger?

You talk about weight-loss methods through history, including Lord Byron drinking vinegar water. Why do smart people try wacky, unproven techniques?
Often people will see somebody else do it, and it seems to work for them. You always have the beauty secrets of the stars. Once you have some famous people saying, "This is how I did it," then everyone does it.

What inspired you to write your book, especially given that you're slim and don't diet?
If I had a weight problem, I think I couldn't have written the book. It would have looked like special pleading, like it's her own excuse for herself. My entire career, I've been reporting in dribs and drabs on the science of body weight. One study after another would come out and say identical twins reared apart would have the same body weight. Somehow the big picture never was there. If you see the popular wisdom on dieting, it's just, "Eat less and exercise more."