Megan McArdle interviews Paul Campos, author of The Obesity Myth:

Paul: I know for a fact (because they’ve told me) that some public health officials engage in what they think of as a noble lie about the effects of physical activity on weight, because they know people won’t become more active just to be healthier.

Megan: Is there any evidence this works? Don’t people just stop going to the gym when they notice they haven’t lost any weight?

Paul: Of course. People aren’t dumb. They do the experiment, the experiment doesn’t work in the vast majority of cases, so they quit until they get desperate again. Or (like the upper West Side women) they stay on a permanent restricted lifestyle that the vast majority of people don’t have the combination of willpower and social privilege to maintain. There’s an important class angle here. Thinness is a sign of social status, and is to some extent a product of it, which is one reason — probably the main reason — why it’s so prized, especially among women.

Megan: An economist recently pointed out that we don’t encourage people to move to the country, even though rural people live more than three years longer than urban people, and the difference in their healthy life expectancy is even more outsized. Nor do we encourage people to find Jesus or get married. We target “unhealthy” behaviors that are already stigmatized.

Paul: Right, as Mary Douglas the anthropologist has pointed out, we focus on risks not on the basis of “rational” cost-benefit analysis, but because of the symbolic work focusing on those risks does — most particularly signalling disapproval of certain groups and behaviors.  In this culture fatness is a metaphor for poverty, lack of self-control, and other stuff that freaks out the new Puritans all across the ideological spectrum, which is why the war on fat is so ferocious — it appeals very strongly to both the right and the left, for related if different reasons.

Megan: And now a convenient scapegoat for our health care costs: if we can just eliminate the folk devils, we can have a new national health care program, and more room on the bus, for free!

Paul: Yes it’s a low-calorie free lunch.

That “economist” is me I think.  Hat tip to Robert Wilbin.