Two recent studies have produced starkly conflicting estimates of the annual number of deaths attributable to obesity in the United States. Mokdad et al. (2004) estimated that poor diet and exercise accounted for 400,000 deaths in 2000, making this the second-leading actual cause of death. In contrast, Flegal et al. (2005) estimated that obesity was associated with 111,909 deaths in 2000. Both studies were published in The Journal of the American Medical Association, and both studies included authors affiliated with the Centers for Disease Control and Prevention (CDC).
The conflicting estimates have greatly animated the debate on obesity policy. The Mokdad et al. study has frequently been used to underscore concerns about increasing obesity in the United States; some researchers and policy makers have proposed voluntary and regulatory policies to prevent obesity. Critics of such policies quickly cited the Flegal et al. study as proof that the obesity epidemic is “overhyped” and that policies to reduce obesity are unnecessary.
In this issue brief, we explain how the studies arrived at their differing estimates. Understanding the differences between the estimates will illuminate future debate about obesity and identify areas where additional study is needed. In comparing and contrasting the studies, we focus on five areas: differences in scope, errors, differences in variables, differences in methods, and differences in data.