Over the past thirty-five years, the U.S. adult obesity rate has more than doubled from roughly 15% to 35%, reflecting a general diffusion of obesity across all segments of the adult population (USDHHS). Obesity is a concern because it increases the risk for cardiovascular diseases, diabetes, and most forms of cancer, except for lung. Earlier studies of obesity of U.S. adults have largely focused on data in a single cross-section or one round of a panel survey. Chen and Huffman (2010) show that food and drink prices significantly affect U.S. women’s probability of being obese but not for men. However, the impact of individual food and drink prices are not always as expected.