Obesity is becoming a serious issue in many developing countries, with negative implications for economic growth and human wellbeing. While previous micro level studies on obesity have mostly used cross-section data, we analyze trends and determinants with panel data from Indonesia. Over the past 20 years, obesity has increased remarkably in Indonesia across all population groups, including rural and low income strata. The problem is particularly severe among women. Panel regressions confirm that changing food consumption patterns, coupled with decreasing physical activity, directly contribute to this trend. From a policy perspective, nutrition awareness and education campaigns, combined with programs to support leisure time exercise especially for women, seem to be most promising to contain the obesity pandemic.