Obese people incur higher health care costs at a given point in time, but how rising obesity rates affect spending growth over time is unknown. We estimate obesity-attributable health care spending increases between 1987 and 2001. Increases in the proportion of and spending on obese people relative to people of normal weight account for 27 percent of the rise in inflation-adjusted per capita spending between 1987 and 2001; spending for diabetes, 38 percent; spending for hyperlipidemia, 22 percent; and spending for heart disease, 41 percent. Increases in obesity prevalence alone account for 12 percent of the growth in health spending.