In 2030, 20 percent of Americans are predicted to be 65 years or older, almost a twofold increase since 2000. Given the current obesity epidemic, obesity among older adults is expected to rise as well, with important economic and health implications. Arterburn and colleagues used prediction models to estimate the prevalence of obesity in 2010 and compared their prediction with the Healthy People 2010 goals of a 60 percent prevalence of normal weight persons older than 60 years and a respective 15 percent prevalence of obesity in the same age group. Using National Health and Nutrition Examination Survey data, age-specific prevalence of normal weight and obesity was estimated for 1990 and 2000. Data were projected by birth cohort for 2010. Best-, middle-, and worst-case scenarios were constructed, assuming that the prevalence of obesity would change at its lowest absolute rate, at a mean rate of change, and at its highest observed rate, respectively.

In 1990, about one fourth of persons 60 years or older were obese (23.6 percent) compared with 38.2 percent normal-weight persons in that age group. By 2000, these percentages were 32.0 and 30.6 percent, respectively. In the best-case scenario, obesity would increase to 33.6 percent; in the middle-case scenario, the prevalence would rise to 37.4 percent, and in the worst case, this number would be 39.6 percent. Normal weight would decrease correspondingly to 31.0, 26.7, and 24.7 percent. None of these estimates approaches the 2010 goals of 15 and 60 percent for each category. Using the middle-case scenario absolute numbers, there would be an additional 400,000 obese Medicare-eligible patients per year up to 2010.

The worst-case scenario is based on estimates that there will be no substantial improvements in obesity prevention and treatment in the next several years, and is therefore likely to be the most accurate.

What is not known are the mortality implications of these findings. The authors conclude that studies looking at obesity-associated mortality risk in patients 75 years and older have yielded conflicting results. In addition, voluntary and involuntary weight loss in older patients has been associated with increased mortality; however, voluntary weight loss appeared to be protective in another analysis. Chronic conditions such as hypertension, diabetes, and cardiovascular disease increase at a higher rate in obese persons than in normal-weight persons, so it is likely that t hese conditions will continue to increase in older age groups. In addition, quality of life and functional ability will likely decline in older obese Americans. It also appears that older obese patients will use more health services and incur higher health care costs compared with their normal-weight peers.