Life expectancy has been increasing across the developed world. As you report, life expectancy in America is now lagging behind countries like Japan, Britain, and Germany, and there is a growing debate whether this is due to obesity (“Long Live the Fat American,” July 2, 2011). Roughly one in three American adults is deemed obese at this juncture. Of course, obesity increases disability, which increases obesity, and so forth. Although medicine is now helping obese people live longer, there is only so much the good doctors can do. But this is not the whole story. Obesity is a phenomenon associated with economic development. It is hardly limited to America alone. In time, countries such as Japan, Britain, and Germany may experience problems with longevity on account of obesity. And the debate about the rôle of obesity in limiting longevity is likely to spread across the developed world. With a vengeance, too.