How Does Obesity in Adults Affect Spending on Health Care?

September 8, 2010

Over the past two decades, the adult population in the United States has, on average, become much heavier. From 1987 to 2007, the fraction of adults who were overweight or obese increased from 44 percent to 63 percent; almost two-thirds of the adult population now falls into one of those categories. The share of obese adults rose particularly rapidly, more than doubling from 13 percent to 28 percent. That sharp increase in the fraction of adults who are overweight or obese poses an important public health challenge. Those adults are more likely to develop serious illnesses, including coronary heart disease, diabetes, and hypertension. As a result, that trend also affects spending on health care.

A CBO issue brief released this afternoon examines changes over time in the distribution of adults among four categories of body weight: underweight, normal, overweight, and obese. Those categories are defined in federal guidelines using a measure known as the body-mass index—a measure that standardizes weight for height. CBO analyzes how past changes in the weight distribution have affected health care spending per adult and projects how future changes might affect spending going forward.

According to CBO’s analysis of survey data, health care spending per adult grew substantially in all weight categories between 1987 and 2007, but the rate of growth was much more rapid among the obese (defined as those with a body-mass index greater than or equal to 30). Spending per capita for obese adults exceeded spending for adults of normal weight by about 8 percent in 1987 and by about 38 percent in 2007. That increasing gap in spending between the two groups probably reflects a combination of factors, including changes in the average health status of the obese population and technological advances that offer new, costly treatments for conditions that are particularly common among obese individuals.

A relatively simple set of calculations using survey data indicates that if the distribution of adults by weight between 1987 and 2007 had changed only to reflect demographic changes, such as the aging of the population, then health care spending per adult in 2007 would have been roughly 3 percent below the actual 2007 amount. Similar calculations for three different scenarios show the potential effects of different trends in adults’ body weight on future health care spending. In all cases, CBO assumes per capita health care spending will continue to grow faster for adults whose weight is in the above-normal categories. CBO’s assumptions and findings for the scenarios are as follows:

  • First, CBO assumed that there will be no future changes in the distribution of adults by body weight, and the prevalence of obesity will remain at the 2007 rate of 28 percent. If so, per capita spending on health care for adults would rise by 65 percent—from $4,550 in 2007 to $7,500 in 2020—largely as a result of rapidly increasing health care spending for all adults regardless of weight. (All dollar figures are in 2009 dollars.)
  • Alternatively, CBO assumed a rising prevalence of obesity, matching recent trends. In that scenario, the prevalence of obesity would rise to 37 percent by 2020, and per capita spending would increase to $7,760—about 3 percent higher than spending in the first scenario.
  • CBO also assessed the impact of a possible reversal in recent trends. In that scenario, the prevalence of obesity among adults would drop to 20 percent by 2020. Per capita spending would increase to $7,230—about 4 percent lower than spending in the first scenario.

Because lower rates of obesity are associated with better health and lower health care spending per capita, there is considerable interest in devising policies that would reduce the fraction of the population that is obese. However, the literature to date suggests that the challenges in reducing the prevalence of obesity are significant. How reducing obesity would affect both total (rather than per capita) spending for health care and the federal budget over time is not clear, for reasons discussed in the brief.

This issue brief was prepared by Noelia Duchovny of CBO’s Health and Human Resources Division and Colin Baker (formerly of CBO).