Lovely obesity paper out from Shin-Yi Chou and others at the National Bureau of Economic Research. The causes of obesity in America as cited by the paper are similar to what you’ve heard elsewhere, but also intriguingly different, with gas taxes, clean indoor air laws, and per capita restaurants counts all playing roles:
This paper employs micro-level data from the First, Second, and Third National Health and Nutrition Examination Surveys to determine the effects that various state-level variables have on body mass index and obesity. These variables, which include the per capita number of restaurants, the gasoline tax, the cigarette tax, and clean indoor air laws, display many of the expected effects on obesity and explain a substantial amount of its trend. These findings control for individual-level measures of household income, years of formal schooling completed, and marital status.