This paper provides a theoretical and empirical examination of the long-run growth in weight over time. We argue that technological change has induced weight growth by making home-and marketproduction more sedentary and by lowering food prices through agricultural innovation. We analyze how such technological change leads to unexpected relationships among income, food prices, and weight. Using individual-level data from 1976 to 1994, we then find that such technology-based reductions in food prices and job-related exercise have had significant impacts on weight across time and populations. In particular, we find that about forty percent of the recent growth in weight seems to be due to agricultural innovation that has lowered food prices, while sixty percent may be due to demand factors such as declining physical activity from technological changes in home and market production.

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.

Recent innovations in biomedicine seem poised to revolutionize medical practice. At the same time, disease and disability are increasing among younger populations. This paper considers how these confluent trends will affect the elderly's health status and health care spending over the next thirty years. Because healthier people live longer, cumulative Medicare spending varies little with a beneficiary's disease and disability status upon entering Medicare. On the other hand, ten of the most promising medical technologies are forecast to increase spending greatly. It is unlikely that a "silver bullet" will emerge to both improve health and dramatically reduce medical spending.