4 January 2013
Is it really healthy to be overweight?
In the news recently is a meta-analysis by Flegal et al. (2013) that found that overweight and mildly obese people actually lived longer than those who were normal weight or thin. The authors list, as possible explanations, the "earlier presentation of heavier patients, greater likelihood of receiving optimal medical treatment, cardioprotective metabolic effects of increased body fat, and benefits of higher metabolic reserves." It should be pointed out that the first two explanations have nothing to do with health per se; hence the rash exuberance of Paul Campos in the New York Times ("Our Absurd Fear of Fat") seems to be ill-founded. As for the basic premise, I'm a bit skeptical since we already know that obesity's associated with a wide range of medical conditions that often do us in--high blood pressure, diabetes, high cholesterol, most cancers, and so on. There's also the literature on calorie restriction (CR), which clearly shows a marked advantage for low-calorie intake and a corresponding low BMI. In the medical literature, CR is often described as the only intervention that's currently known to actually slow aging. My guess is that the Flegal team's meta-analysis has failed to identify and account for some lurking variables (for example, unreported amphetamine use by thin subjects and so on).