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The bigger the healthier: are the limits of BMI risk changing over time?

Henderson RM

University of Chicago, Graduate School of Business, Center for Population Economics and Department of History, Room 367, 5807 South Woodlawn Avenue, Chicago, IL 60637, USA. r-henderson@uchicago.edu

The body mass index (BMI) is often used as a predictor of overweight and obesity. There is, however, an important debate among international specialists as to what the risk limits should be, and where the cut-off points should be located. In the United States, for instance, adults with a BMI between 25 and 30 are considered overweight, while adults with a BMI of 30 or higher are considered obese. Nevertheless some researchers, especially in developing countries, claim that the limits established for the US are too permissive, and that the threshold to define obese adults should be set lower for other nationalities and ethnicities. This paper analyzes the mortality risks for different BMI levels of two populations of American adult men. The first population lived during the last quarter of the 19th century and the early 20th century. These men were drawn from a random sample of Union Army veterans who fought during the American Civil War (1861-1865). A contemporary sample of men was drawn from the first wave of the National Health and Nutrition Examination Survey (NHANES I) conducted between 1971 and 1975. The results indicate that the frontier of overweight and obesity are expanding over time, such that the potential risk is nowadays associated with higher levels of BMI. The finding may imply that differences in BMI cut-off points are not only cross ethnic, but also occur for similar ethnicities across time.

Published 25 October 2005 in Econ Hum Biol, 3(3): 339-66.
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