Secular Declines in the Association Between Obesity and Mortality in the United States

life expectancy has been increasing in the united States for well over a cen-tury. while some analysts, including the Social Security administration, have projected a continued rise over the next seven decades (Board of trustees 2009), others have argued that the substantial rise in obesity could cause life expectancy to level off or decline within the first half of this century (olshan-sky et al. 2005). Recent research on the joint effects of obesity and smoking on uS life expectancy forecasts that the negative effects of rising obesity will potentially overwhelm the positive effects gained from declining smoking rates, retarding increases in life expectancy (Stewart, Cutler, and Rosen 2009). the uS has witnessed substantial increases in the prevalence of obesity. adult obesity (body mass index [Bmi] ≥30.0 kg/m2) has more than doubled over the past three decades, and obesity among school-aged children (Bmi-for-age ≥95th percentile) has tripled (Flegal et al. 2010; ogden et al. 2002). Projec-tions of the effect of obesity on life expectancy, however, generally assume that the risk of death imposed by obesity has been and will remain stable (Stewart, Cutler, and Rosen 2009; olshansky et al. 2005). a large number of studies have shown that class i obesity (Bmi 30.0– 34.9) and class ii/iii obesity (Bmi ≥35.0) have strong associations with mor-tality (Prospective Studies Collaboration 2009; Hu et al. 2004; mokdad et al