But even if you don't eat more, food is being stored as fat as a priority instead of doing other useful things with it, so you can undereat and be both obese and malnourished, by eating the wrong types of food.

You can induce all kinds of freakish pathologies by eating the wrong types of food; that's nothing new. Simultaneous obesity and malnourishment is common in poor communities in the U.S. because of diets that are high in calories but deficient in other ways. I seriously doubt anyone could be obese and calorie-malnourished in the absence of serious medical issues or radical inconsistency in food availability. The existence of odd pathologies like Taubes' lipodystrophy cases doesn't say anything about the vast majority of people.

Taubes acts like the mere existence of these pathologies is mind-blowing. But it's just common sense: the process of storing and metabolizing body fat isn't physically inevitable. It's complicated. There are all kinds of ways it could be suppressed, and you expect that as with any other biological process, there's going to be natural variation in the population, including people where the process goes wrong in an odd way. That isn't a daring supposition. That's just the way any ordinary doctor or biologist would think. The question is dealt with every time a new drug is studied -- how will different people respond to it? Vioxx was a scandal because detecting rare harmful side effects of treatments that work well in most people is routine. The idea that a "healthy" diet might harm some people, especially people already suffering from a metabolic disorder, would not blow anyone's mind. Look at all the research into nutrition for diabetics!

Anyway, I still don't see anything new here. Theoretical speculation is fine and dandy, but the question is, what actually happens? If you practice reasonable calorie restriction on a reasonable diet, your body will adjust. It will not kill you or permanently harm you. It will certainly threaten you and try to convince you that you're dying. Everybody knows that when you decrease your food intake, your body complains. It tries to make you eat more. It makes you feel tired. It makes you feel like exercising would be a bigger mistake than drunk-dialing your boss's teenage daughter. But if you go against those feelings, your body's doomsday predictions don't come true. If the situation described by Taubes actually prevented healthy weight loss -- your body starving certain systems of calories in order to spare body fat -- you would expect that people following reasonable diets and exercise could end up unhealthy. And it doesn't happen.

That isn't just an assumption. There are some seriously strong-willed people out there who are pathologically devoted to low body fat and/or suffer from body dysmorphic disorders. There are also some seriously strong-willed people who are dedicated to athletic performance but rather dumb about how they pursue it. We know people can persist in unhealthy habits to the point of breakdown -- it happens all the time. It's not like there's a great uncharted domain out there of freakish consequences that could result from weird practices. Crazy, stupid, and/or mentally ill people have explored the weirdo options pretty thoroughly, sometimes with gruesome results. So why haven't we seen any gruesome outcomes from the diets that are considered healthy according to the conventional wisdom? The only possible conclusion is that whatever pathological responses our bodies might have to healthy diets -- such as starving important systems to spare body fat -- don't persist over the long term in people with an overabundance of body fat.

In any case, from an overweight person's point of view rather than a public policy standpoint, the only practical question is what will happen if you eat a reasonable diet and exercise. The answer is that if you follow any one of a bunch of reasonable diets, from Ornish to Atkins, you will lose weight and be healthier, and if you exercise, you will be even healthier. I get annoyed when people like Taubes, knowing how eager people are to believe otherwise, go through a complex song and dance that encourages people to believe otherwise even though he doesn't seem to believe otherwise himself.