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October 01, 2007

The Weight Loss Post

Apparently, everything we think we knew about weight loss is wrong. Here is Gary Taubes in the New York Magazine:

For the last 60 years, researchers studying obesity and weight regulation have insisted on treating the human body as a thermodynamic black box: Calories go in one side, they come out the other, and the difference (calories in minus calories out) ends up as either more or less fat. The fat tissue, in this thermodynamic model, has nothing to say in the matter. Thus the official recommendations to eat less and exercise more and assuredly you'll get thinner. (Or at least not fatter.) And in the strict sense this is true -- you can starve a human, or a rat, and he will indeed lose weight -- but that misses the point. Humans, rats, and all living organisms are ruled by biology, not thermodynamics. When we deprive ourselves of food, we get hungry. When we push ourselves physically, we get tired. Our bodies, like all living organisms, have evolved a fantastically complex web of feedback loops.

After decades of being told that the relevant factors are diet and exercise, it seems instead that twin pillars of weight regulation are appetite and metabolism.

Unfortunately, these two factors are inside that black box. We don't fully understand them, but we do know that diet and exercise can influence them in counterproductive ways. Taubes spends much of his article detailing how exercise can not makes us thin. Part of the reason is our metabolism does not respond to exercise in ways that sustain caloric losses. Another is that vigorous exercise increases our appetite: the more one works out, the hungrier one becomes.

For its part, there is now considerable evidence that diets don't work; initial losses are small, and in the long-term, dieters even end up gaining. Diet has complex interactions with both appetite and metabolism, as Gina Kolata explains in an excerpt from her new book, reprinted here in the New York Times. Kolata endorses the view that every individual has a set range of weight, 10-20 pounds, in which they will normally fluctuate. This range acts like a thermostat, and when pushed outside that range, the "complex web of feedback loops" will return a person to his normal weight through metabolism and appetite.

We can work down to the lower end of each of our ranges, so it is possible to lose 10 lbs. with some self-discipline. But even this expenditure of will-power takes a lot of effort, and remember, will-power is a limited resource. How much harder must it be for the obese, who must push far below their range to fall into what our culture deems normal? Their conscious expenditure of will-power must overcome crippling biological impulses. Their bodies are sending out every signal that they are starving, metabolism slows, and appetite skyrockets. Kolata summarizes research with weight loss subjects:

The Rockefeller subjects also had a psychiatric syndrome, called semi-starvation neurosis, which had been noticed before in people of normal weight who had been starved. They dreamed of food, they fantasized about food or about breaking their diet. They were anxious and depressed; some had thoughts of suicide. They secreted food in their rooms. And they binged . . .

Eventually, more than 50 people lived at the hospital and lost weight, and every one had physical and psychological signs of starvation. There were a very few who did not get fat again, but they made staying thin their life's work, becoming Weight Watchers lecturers, for example, and, always, counting calories and maintaining themselves in a permanent state of starvation.

In light of these findings, it is absurd to ascribe obesity to sloth or gluttony. Likewise is it wrong to think lean people simply have an excess of will-power. Taubes explains:

They are people whose bodies are programmed to send the calories they consume to the muscles to be burned rather than to the fat tissue to be stored -- the Lance Armstrongs of the world. The rest of us tend to go the other way, shunting off calories to fat tissue, where they accumulate to excess.

We are bound by our biology. Kolata reports that our weight ranges have many determinants, but genetics may account for up to 70% of the variation. That's rather discouraging, especially since it is unknown what comprises the other 30% (obviously, some sort of environmental factors -- here are some obscure ones). And yet I share Jane Galt's skepticism about genetic determinants, since inheritance cannot adequately explain the weight gain epidemic. It will be interesting to see how malleable appetite and metabolism are.

And so we have a new frontier in weight regulation research. Hopefully, science will follow where fads have gone before. The Atkins Diet is a theoretical approach to changing metabolism, but it ultimately fails (among other reasons) because it is not sustainable. For whatever reason, we have an innate appetite for carbohydrates. Seth Roberts' Shangri-La Diet is an interesting stab from the other direction; it claims to be able to perpetually lower appetite. In a world of hundreds of diets, I suppose it's natural that at least two would have stumbled on the new insights. But maybe now we can stop groping in the dark.

Posted by Zach Wendling at October 1, 2007 07:09 AM

Comments

Posted by: Eric Seymour at October 1, 2007 09:50 AM | permalink

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