Friday, August 15, 2008

On health and weight

The Speculist discusses health and weight in the context of a pill that helps you retain the benefits of weight loss without staying on the food and exercise program that helped you attain it.

In study after study over the course of the past century, the number of clinical trial subjects who have kept more than 40 pounds off for a period of five or more years is vanishingly rare. The number that's thrown around on Dean's World is 0.1%, although I haven't seen where Dean specifically raised this number, only where people arguing with him have. So if we can name people who have met the criteria -- Jared comes to mind -- we have only found an example of that 0.1% of the population for whom diet and exercise is an effective long-term obesity cure. Likewise, the participants in the National Weight Control Registry (NWCR) study were asked to participate if they had already achieved a certain level of long-term weight loss -- it's just another example of this same selection bias.

It's like "proving" that the lottery is a smart bet because somebody won!


And in the comments, jaed makes a good point about how hard it is to accept scientific evidence when it contradicts our common sense:

I wondered for a long time why, in the face of much data indicating that starvation dieting, alone or in combination with exercise, fails to permanently change body shape, we still have people chirping "All you have to do is eat less and move more, and the pounds will melt away like magic!" every time this subject comes up. I finally decided it's because people overgeneralize from their own experience.

[...]
Because [the common wisdom is that] everyone naturally has the same body type, and deviations must be caused by differences in eating and exercise levels.

Written out like that, the fallacy is pretty obvious. But people still stick to it. There's an ideal shape, and if you fall short of it, it's All Your Fault, and we will keep saying that until you admit you're a bad fatty and repent - preferably by limiting your food intake to the point of causing yourself permanent metabolic damage. Whereupon we will announce that you have "failed". Makes me berserk, that kind of ugly thinking.

Meanwhile, the result of this mindset that you can change your body type by sheer force of will is:

- Fat people feel perpetually guilty, shamed, and afraid. They try to do the impossible (change their fundamental body shape) and feel like weak-willed failures when it predictably doesn't work.

- Thin people feel like they have nothing to worry about healthwise, even if they eat gak and never exercise. They're thin. And that means they're healthy, right?

- People who exercise, feel better, and obtain health benefits but don't lose a lot of weight feel as though they might as well not bother - after all, thin is healthy, and all this exercise isn't making them thin, so it can't possibly have a good effect on their health, right? [...]

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