Morbid Obesity Rates Continue to Rise Rapidly in the United States

Published in: International Journal of Obesity, v. 37, no. 6, June 2013, p. 889-891

Posted on RAND.org on September 01, 2012

by Roland Sturm, Aiko Hattori

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Research Question

  1. What has been the trend in rates of clinically severe or morbid obesity since 2000 in the U.S.?

Clinically severe or morbid obesity (body mass index (BMI) >40 or 50 kg m−2) entails far more serious health consequences than moderate obesity for patients, and creates additional challenges for providers. The paper provides time trends for extreme weight categories (BMI >40 and >50 kg m−2) until 2010, using data from the Behavioral Risk Factor Surveillance System. Between 2000 and 2010, the prevalence of a BMI >40 kg m−2 (type III obesity), calculated from self-reported height and weight, increased by 70%, whereas the prevalence of BMI >50 kg m−2 increased even faster. Although the BMI rates at every point in time are higher among Hispanics and Blacks, there were no significant differences in trends between them and non-Hispanic Whites. The growth rate appears to have slowed down since 2005. Adjusting for self-report biases, we estimate that in 2010 15.5 million adult Americans or 6.6% of the population had an actual BMI >40 kg m−2. The prevalence of clinically severe obesity continues to be increasing, although less rapidly in more recent years than prior to 2005.

Key Findings

Morbid obesity rates in the United States continue to rise rapidly.

  • The relative rate of increase is similar across population subgroups, even though the prevalence at every point in time differs across groups.
  • Trajectories do not differ across groups, but the most disadvantaged group appears to be just a few years ahead of others.

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