Related To: The Unfinished Mystery of the Shangri-La Diet and Missed Distinctions
Megan McArdles blogs an interview with Paul Campos, author of The Obesity Myth. I'll let anyone who is interest read the whole thing, but here's some interesting excerpts:
I mean, there's no better established empirical proposition in medical science that we don't know how to make people thinner. But apparently this proposition is too disturbing to consider, even though it's about as well established as that cigarettes cause lung cancer. So all these proposals about improving public health by making people thinner are completely crazy. They are as non-sensical as anything being proposed by public officials in our culture right now, which is saying something.
It's conceivable that through some massive policy interventions you might be able to reduce the population's average BMI from 27 to 25 or something like that. But what would be the point? There aren't any health differences to speak of for people between BMIs of about 20 and 35, so undertaking the public health equivalent of the Apollo program to reduce the populace's average BMI by a unit or two (and again I will emphasize that we don't actually know if we could do even that) is an incredible waste of public health resources
and
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 diffefence 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.
I am literally so baffled by the thesis presented above I can't bring myself to disagree with it because I must be missing something. I mean, within five minutes on Google I found five studies showing strong correlations between various measures of body fat and coronary heart disease:
In a 14-year prospective study, middle-aged women with a BMI >23 but 25 but <29 had a 72% increased risk
When participants with the highest waist-to-hip ratio were compared with those having the lowest ratio, there was an 80 percent increase in risk.
The risk of any CHD event, a nonfatal event, and a fatal event among adults was positively associated with BMI at 7 to 13 years of age for boys and 10 to 13 years of age for girls.
These prospective cohort studies employed simple indices of body-fat distribution such as waist-to-hip circumference ratio or subscapular skinfold. Their similar results suggested that increased abdominal obesity conferred a two-fold increased risk of ischemic heart disease among middle-aged men.
IAF and trunk fat were consistently positively related to CVD risk factors, whereas leg fat was consistently negatively related to CVD risk, indicating that IAF and trunk fat may put women at increased risk of developing CVD.
If I was willing to give it an hour, I'm sure I could have found sixty of them, and I know there are many similar studies about type II diabetes, cerebrovascular disease, et cetera. Because many of these are prospective studies, they have a better ability to show causality than longitudinal studies (although still not perfect). And another five minutes on Google find me several interventional studies about how turning fat people into thin people improves their health:
Our study has shown that weight loss of as little as 6.5 percent in individuals with [metabolic syndrome] results in substantial reductions in blood pressure, glucose, triglycerides and total cholesterol, all factors that lead to heart disease,’ MDBHVC director Christie Ballantyne said. These impressive results occur early in the weight loss, well before individuals even begin to approach their ideal body weight,’ Ballantyne said.
Weight loss was significantly associated with lower rate of the composite outcome after adjustment for age, sex, smoking, dyslipidemia, diabetes, hypertension, myocardial infarction, and obese status [hazard ratio (HR)=0.62; P=0.018]. Subgroup analysis showed that patients who lost weight had favorable outcomes both in patients with BMI <25 (HR=0.32; P=0.035) and those with BMI ≥25kg/m2 HR=0.64; P=0.032.
So what exactly is the thesis? That all of these studies are flawed in the same way? That there's some vital causal step that's been left out? Surely the author must know about these, right?
I think the story goes like this: there are correlations between weight and health. There are disputes, but let us skip that and assume for the sake of argument that thin people live longer than fat people. The next question is whether this is causal. If a fat person makes a big effort and becomes thin, will he have a long life, just like a person who was thin to begin with?
We can fill in the details of what the experiment looks like. We start with 200 fatties who want to get thin, and a random assignment of 100 to the control group, who get the usual crap... (read more)