Obesity could have serious consequences for older cohorts. We used a microsimulation to estimate lifetime costs, life expectancy, disease, and disability for seventy-year-olds based on body mass. Obese seventy-year-olds will live about as long as those of normal weight but will spend more than 39,000 dollars more on health care. Moreover, they will enjoy fewer disability-free life years and experience higher rates of diabetes, hypertension, and heart disease. Medicare will spend about 34 percent more on an obese person than on someone of normal weight. Obesity might cost Medicare more than other diseases, because higher costs are not offset by reduced longevity.