Apr 8, 2007
Published in: Public Health, v. 121, no. 7, July 2007, p. 492-496
Posted on RAND.org on December 31, 2006
BACKGROUND: It is well known that citizens of developed countries are more likely to be overweight than they were 20 years ago. The most serious health problems are not associated with overweight or moderate obesity, however, but with clinically severe or morbid obesity (e.g. more than 100 pounds (45 kg) overweight). There is no reason to expect that morbid obesity trends parallel overweight or moderate obesity. If morbid obesity is a rare pathological condition that has biological causes, the more than 10-fold increase in bariatric surgery procedures over the past eight years in the USA could have even lowered the prevalence of morbid obesity--and may very well stem the problem in other countries. OBJECTIVE: To estimate trends for extreme weight categories (BMI>40 and >50) for the period between 1986 and 2005 in the USA, and to investigate whether trends have changed since 2000. METHODS: Data from The Behavioral Risk Factor Surveillance System (a random-digit telephone survey of the household population of the USA), for the period from 1986 to 2005, were analysed. The main outcome measure was body mass index (BMI), calculated from self-reported weight and height. RESULTS: From 2000 to 2005, the prevalence of obesity (self-reported BMI over 30) increased by 24%. However, the prevalence of a (self-reported) BMI over 40 (about 100 pounds (45 kg) overweight) increased by 50% and the prevalence of a BMI over 50 increased by 75%, two and three times faster, respectively. The heaviest BMI groups have been increasing at the fastest rates for 20 years. CONCLUSIONS: The prevalence of clinically severe obesity is increasing at a much faster rate among adults in the USA than is the prevalence of moderate obesity. This is consistent with the public health idea that the population weight distribution is shifting, which disproportionately increases extreme weight categories. Because comorbidities and resulting service use are much higher among severely obese individuals, the widely published trends for overweight/obesity underestimate the consequences for population health. The aggressive and costly expansion of bariatric surgery in recent years has had no visible effect on containing morbid obesity rates in the USA.