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and mortality is stronger; (3) the increasing severity of obesity; and (4) the increasing duration of obesity.

In an effort to be responsive to the question at hand (i.e., Can obesity account for cross-national differences in life-expectancy trends at age 50?), the following review focuses on BMI in older cohorts. First, we examine international trends in obesity and life expectancy. Second, we review the association between obesity and mortality, prioritizing estimates that are generalizable to the U.S. population. Third, we provide estimates of the effect of obesity on life expectancy in the United States. Fourth, we discuss limitations in the use of BMI to predict mortality and the implications of these limitations for cross-national comparisons. Finally, we discuss implications of rising obesity rates for future trends in life expectancy and other population health indicators. Throughout the review, we rely on published results and our own analysis of the National Health and Nutrition Examination Survey (NHANES), a nationally representative repeated cross-sectional survey of U.S. adults that includes both a questionnaire and a physical exam, including height and weight measurement (National Center for Health Statistics, 2009).

INTERNATIONAL TRENDS IN OBESITY AND LIFE EXPECTANCY

The World Health Organization (WHO) defines obesity as a BMI (dividing weight in kg over squared height in meters) of 30kg/m2 or more. Figure 6-1 presents obesity prevalence estimates for adults in 10 countries over time.1 Among adult men, the United States has the highest obesity prevalence at all observed time points. In approximately 1978 (data collected 1976-1980), the prevalence of obesity among men in the United States was 13 percent. Around the same time, the prevalence varied from a low of 0.8 percent in Japan to a high of 12 percent in Canada. By 2003, the prevalence of obesity among American men had more than doubled, to 32 percent. The most recent estimates from other countries show that 23 percent of British and Canadian men are obese, followed by 19 percent of Australian men, 12 percent of Danish, French, and Spanish men, and 10 percent of Dutch men. Only men in Italy and Japan have an obesity prevalence below 10 percent.

Overall patterns are similar among adult women. Around 1978, the prevalence of obesity among women in the United States was already 17 percent, and it rose to 35 percent in 2003. The prevalence of obesity

1

Age ranges vary. The majority of data sources were designed to be nationally representative (with the exception of data before 1999 in Australia and all data from the Netherlands, which were collected in major cities only). Where surveys spanned multiple years, prevalence estimates are shown based on the midpoint of survey collection.



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