For 20 years, Neris Thomas treated dieting like her second job, but it wasn't until she teamed up with overweight acquaintance India Knight that the pounds came off for good. What clicked? The buddy system. Now the pair is down a collective 140 pounds and Neris and India's Idiot-Proof Diet, their hybrid handbook of low-carb program and "we've so been there" pep talk - already a best seller in Britain - has landed stateside. Here, they sound off on sugar, spandex, and the way women sabotage each other.

Marie Claire: What was the catalyst here?
Neris Thomas: I was thinking, Why is it that I'm a successful woman who's got a fantastic film company, a daughter, a marriage - everything's great - and yet I can't control myself enough to fix this thing that's made me unhappy for 20 years? And you know, there was a lot of chafing going on, a lot of rubbing of legs.
India Knight: For me, part of it was turning 40 and deciding, I'm not going to walk around for 30 more years wearing tents. But I didn't think there was a diet that would work - I was already so far gone.

MC: Instead, you came up with a low-carb regimen - basically a modified Atkins - and found that it could really work for you.
IK: We cherry-picked from existing diets until we had something we could live with, then ran it past a couple of doctors. I've just come back from a lunch of sea bass, spinach salad, and a vodka tonic - just a normal pub lunch in London. With this way of eating, nobody notices you're on a diet.

MC: You're big on having a "diet buddy" - sharing every step of the experience with someone, even when you're out of sync.
NT: I told India, "I'm never going to stick to this unless we really talk to each other about what's going on inside our heads." I can't say it was easy - India stuck to her diet, and I felt like I was flailing around. But what got me back on track were the e-mails. We wrote thousands of them. I needed that support, and I needed somebody to be honest with.

MC: So is it talk therapy that sets your plan apart?
IK: The key to this is the emotional stuff. We can all do the methods for two weeks or a month - eating all grapefruit or all eggs or whatever - but our diet forces you to ask yourself hard questions and look at the reasons you got to this point. Once you unravel that, the rest falls into place.

MC: You also encountered a lot of resistance from female friends who found out you were dieting. What was that like?
NT: You get so much aggression if you say, "I'm on a diet." It's like people can't accept you're doing something for yourself, which is pretty scary if you dwell on it too long.
IK: If your girlfriend says you look great when you weigh 350 pounds, part of you thinks, That's not what a friend says. It has to do with the complexity of female relationships. Subconsciously, having a fat friend enables you to order dessert.

MC: Why is food so fraught for women?
IK: I could write five other books about women and food. It comes down to that weird female competition, which can be so self-punishing. But I really believe, in an old-fashioned way, that female friendship is special and that it will win out over all this other crap in the end.

MC: Is this eating style suitable for people who don't want to drop a ton of weight but want to feel better?
b>IK: It's really only for people who have a substantial amount of weight to lose. But I think sugar is the devil, and even if you're not overweight, incredible things can be accomplished by cutting it out - like eliminating mood swings and energy crashes.

MC: Best part of being 70 pounds lighter?
IK: I just look immeasurably better. Now I can go to any store in a fashion crisis - not just the spandex section like before.
NT: I kind of thought everything suited me when I lost the weight. We both spent so much money, it was a disaster! I'm sure our next book will be Happier Women, Loads of Debt.

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