Many commentators have claimed that farm subsidies have contributed significantly to the “obesity epidemic” by making fattening foods relatively cheap and abundant. But U.S. farm policies have generally small and mixed effects on farm commodity prices, which in turn have even smaller and still mixed effects on the relative prices of more- and less-fattening foods. Other factors have had much more influence on reducing the farm prices of food commodities and the consumer prices of food such that any effects of U.S. farm policies on U.S. obesity patterns must have been negligible. Moreover, while many arguments can be made for changing U.S. farm subsidies, even entirely eliminating the current programs could not be expected to have a significant influence on obesity rates. International evidence reinforces this finding. The countries that support their farmers most strongly tend to have relatively low obesity rates. In these countries the main support for farmers comes through trade barriers and higher consumer prices, which—like U.S. policies for sugar, dairy, orange juice, and beef—discourage consumption and reduce obesity. In contrast with agricultural subsidies, agricultural R&D has had a significant effect in the past on the relative price of food commodities and food, and has the potential to influence obesity patterns in the future, but R&D policy is a very blunt instrument for pursuing public health policy objectives.