The global obesity epidemic has deep socioeconomic roots. Far from being a genetically-determined disease, obesity for most people in the US is the embodiment of social and economic disadvantage. Higher rates of obesity and type 2 diabetes occur among groups with lower education and incomes, some racial/ethnic minorities, and in the more deprived areas. Geocoding of obese persons addresses using geographic information systems (GIS), has allowed us to pinpoint differences in obesity prevalence at the neighborhood scale. Using spatial analyses of health insurance and other data, we have been able to map obesity prevalence at the census tract and even census block level. Such fine-scale maps stand in marked contrast to the state- and county-level maps created by the US Centers for Disease Control (CDC), which tend to mask social disparities and are not useful for health planning purposes. Neighborhood-level analyses point to close links between obesity and poverty, showing that obesity rates are reliably predicted by education, purchasing power and the value of one’s home. In Seattle King County, for every $100,000 in added property values, obesity prevalence dropped by 2%.. In other words, the low cost of dietary energy ($.100 kcal) may be the main predictor of population weight gain. For most of the US population, obesity is an economic issue.