Think fat people could be thin if they really tried? Then Gina Kolata has news for you in Rethinking Thin.

Your conclusions about the near-impossibility of the obese losing a lot of weight and keeping it off could be a solace to them: it's not their fault. Or it could induce fatalism. What impact do you think your book will have?

I wish most people would realize they can't be arbitrarily thin just like they can't be arbitrarily fat, and also, if I had my wish in this world, it would be that somehow we could learn to accept people of different weights just like we accept people of different heights. I run, and in a marathon or any running race, you see people cheering on the laggards. They don't say, why didn't they try harder? Why are they so slow? Yet if you have people who are fat and they're really trying and can't get themselves to be arbitrarily thin, the argument is, if they tried a little harder, they could do it. In a way, weight is like height. You can control it to some extent—like I could have been taller if I'd been better fed as a kid, though I was pretty well fed—but I could never be 5'10" with my genetics.

Do you struggle with weight?

The answer to your question is no, I'm thin and I've never been overweight. I think about food—am I eating too much? I think about, should I eat less tomorrow because I ate more today? But I don't struggle with my weight. When I wrote this book, I purposely tried to keep myself out of it, and the reason is that I feel like, when you write a book like this, it shouldn't look like personal pleading. You almost lose credibility.

So what would you say to all the publishers of diet books: are they engaging in false advertising?

We all like to dream. It's just part of human nature, wanting to remake ourselves. And so I guess the diet book people are selling a dream. They're fun to read, they are. They're very exciting. I started reading this Atkins book, it really sort of carries you along. You say, oh, yeah, look at this person, look at how it transformed their life, that's so wonderful for them. I can see the appeal. I wouldn't say, don't do it. I just wish people would realize it's a dream.