Archive for June, 2011

Why We Get Fat: And What To Do About It, by Gary Taubes   no comments

Posted at 6:28 pm in Book review

It’s no secret that America has an obesity problem. And we know what we need to do about it: eat less and exercise more. Consume less fat. Rely less on animal products. If we can all just control ourselves and eat a low-fat, plant-based diet and get some exercise, everyone will be fine. Right?

That’s certainly the prevalent doctrine, dispensed by more or less everyone except for the authors of a trickle of low-carb diet books. (Confession: until recently, I considered Atkins and co to be utterly misguided.) But does it take into account how our bodies actually work?

Not according to Gary Taubes. In “Why We Get Fat,” he argues that it is carbohydrates, not fat, that cause obesity. An earlier book “Good Calories, Bad Calories” made this point in a much more verbose and technical way; this is his attempt at a more layperson-friendly (though certainly not unscientific) account.

Taubes regards the calories in/calories out model of weight loss as distinctly unhelpful. Sure: to gain weight, I have to eat more than I discard, but what causes this? Is every overweight person really just gluttonous and lazy?

He illuminates matters by describing a group of female rats whose ovaries had been removed. They began eating incessantly and quickly became quite obese. In some cases, though, they were held to their usual diets. These rats also became obese, but in addition, were lethargic, moving only to gather food. Greed and sloth: end of story?

No. Without ovaries, they had no estrogen. Estrogen helps regulate how fat is stored, and prevents it from landing solely in fat, as opposed to, say, muscle cells. In the absence of estrogen, most of the fat that these animals consumed was being stored in their fat cells. This meant that their bodies had no fuel to run on. So they kept eating. Forcibly prevented from eating, they lacked the energy to move. They weren’t getting fat because they were overeating: they were overeating because they were getting fat.

Humans are in the same position: incoming fat can be shunted into storage or treated as fuel.* (And estrogen works the same way, which is probably why women who have had hysterectomies often struggle with their weight .)  Taubes gives a somewhat technical but quite enlightening description of how we process food, with insulin in the starring role. We consume carbs, they’re turned into glucose, our bodies release a wave of insulin to cope with it. Insulin has a variety of effects, none very helpful to anyone who wants to lose weight. In particular, while insulin is elevated, it is impossible to burn anything other than glucose. It doesn’t matter how much fat is sitting around: we can’t burn it. In anyone with chronically elevated insulin, this is obviously a problem. Adding insult to injury, as we get older, we tend to become less sensitive to insulin, and some people become resistant. Obviously, this does not affect everyone equally (genetics plays a big role): we all know people who can eat piles of chocolate without gaining weight. “It may be easier to believe that we remain lean because we’re virtuous and we get fat because we’re not, but the evidence simply says otherwise. Virtue has little more to do with our weight than with our height,” Taubes says. Refined carbohydrates may not cause trouble everywhere, but where there are weight problems, Taubes says, carbs (and our hormonal response to them) are always to blame.

It is impossible to decrease carbohydrate consumption without increasing fat intake. Taubes is fully aware of the environmental and ethical disadvantages of a heavily meat-based diet, though he does not offer a solution. He does, however, address the widespread claim that the key to both weight loss and good health is a low-fat diet. Rather shockingly, he makes a convincing case that its purported beneficial effects are not supported by science.  (There is a revealing discussion of how the government came to claim that they were.) On the contrary, studies seem to show that people on low-carb, high fat diets have improved triglycerides and HDLs. As he points out, for a very long time our species lived chiefly on the fattiest meat it could find: the idea that we require carrots and orange juice isn’t entirely obvious. He dispenses with exercise similarly handily–while unquestionably very important, exercise does not seem to contribute much to weight loss.

David Kessler recently made clear that given that our brains treat combinations of sugar, salt, and fat more or less like heroin, judgmental harumphing isn’t a reasonable response to the obesity crisis. Given the large, intense–and utterly useless–guilt-fest that this country’s discussion of weight still is, this book couldn’t come at a better time.


*This is a simplified description: please do not treat this essay as an endocrinology manual.

Written by Lorin on June 30th, 2011

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