Americans are famously losing the battle of the bulge—two thirds of the adults in the United States are overweight or obese. In "Rethinking Thin: The New Science of Weight Loss—and the Myths and Realities of Dieting" (Farrar, Straus and Giroux, May 2007), The New York Times science and medicine writer Gina Kolata explores why it's so hard to lose weight and keep it off. According to a Consumer Reports survey out this week, 41 percent of the adult population is trying to lose weight and their average goal is a whopping 37 pounds. Kolata talks with NEWSWEEK's Karen Springen about our national obsession with dieting and the science behind weight-loss failures. Excerpts:
NEWSWEEK: The Consumer Reports survey shows that 90 million U.S. adults are currently dieting—and they they're aiming to lose a lot of weight—37 pounds, not just five or 10. Why can't we lose weight on diets?
Gina Kolata: It's interesting how many people diet and how many people diet repeatedly. Sometimes they have unrealistic expectations of what they're biologically able to sustain. For some people, a 30- or 40-pound weight loss is biologically impossible. There are just some things your body won't let you do. On the other hand, I'm not anti-diet. When you start a diet, it's actually very empowering. You feel really good. Usually you're not hungry in the beginning, you feel in control, you're really happy. And then, after awhile, when some of the weight starts coming back, as it usually does, you don't say, "Boy, was I a fool to try a diet." You say, "I failed. I just fell apart. I had that birthday cake and that just set me off. It was my fault." Then another diet comes along. Women also go out and buy cosmetics [hoping to remake themselves]. You're promised if you put this thing on your face, you'll look 20 years old.
So are the diet merchants peddling the same thing as the cosmetics marketers?
It's like they're selling dreams. I don't think there's anything wrong with aspirations and dreams. The problem is when you start to beat up on yourself. You can eat healthy and exercise and do all the things you're supposed to do, and you may not be really skinny. That doesn't mean you're ugly or unacceptable or even out of control. I wish people would realize that most people who've tried to lose weight have tried very, very hard. One guy in the book said, "I've lost and gained an entire person in my lifetime." He realized that he's never going to be free of this desire, this urge to remake himself.
Isn't it a problem if you're always on a diet?
It's a weird thing. It's like a love-hate thing. You hate the fact you're depriving yourself. On the other hand, there is this good feeling of every day you look a little better. You step on the scale and you feel great. It's not necessarily some sort of evil thing to be on a diet.
We constantly see new diet books, like "21 Pounds in 21 Days." How is "Rethinking Thin" different?
This is a book that's going to help you understand why it is you've had so much trouble, why you aren't as skinny as you think you should be. It's to help you understand the biology. I don't think there is a perfect diet. I'm not going to tell you there's a perfect diet. But if you know what scientists know, you'll understand why you've done certain things and why it seems so incredibly easy for that weight to come back on. You'll understand what scientists know about how and why your brain and your genetics are controlling how fat you are and how thin you can become.
Is the bottom line that diets don't work?
They do work. You can lose weight. They can take you from the top of your [weight] range to the bottom. But you can't be necessarily as thin as you think you might want to be, just like you can't run as fast as you think you might want to run. Everyone has their biological limits.
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."
Have you tried any diet?
Yeah, I did. After my first child was born, I went to Weight Watchers and I loved it. I was like a fanatic. The weight just fell right off. Also, when I was in college, my friend and I wanted to get really skinny. I tried insane diets, frozen Metracal [a diet drink] for dinner. It was ridiculous. It was the kind of thing where I don't like to admit I did it. A lot of us did things like that. Once I ate an entire frozen chocolate cake. I'd been so starved. So I do understand.