Increases in clinically severe obesity in the United States, 1986-2000.

We know that Americans are increasingly becoming overweight, but we do not know whether this trend applies to clinically severe obesity (>100 lbs [45 kg] overweight), which is believed to have different causes than typical weight gain. Severe obesity is more serious for an individual's health and creates different challenges for the health care system. This study estimates trends for extreme weight categories between the years 1986 and 2000. The data come from the Behavioral Risk Factor Surveillance System. The dependent variable is weight category according to the body mass index (BMI; calculated as weight in kilograms divided by the square of height in meters) based on self-reported weight and height. Regression models adjust for changes in population characteristics and state participation. Between 1986 and 2000, the prevalence of a BMI (self-reported) of 40 or greater (about 100 lbs [45 kg] overweight) quadrupled from about 1 in 200 adult Americans to 1 in 50; the prevalence of a BMI of 50 or greater increased by a factor of 5, from about 1 in 2000 to 1 in 400. In contrast, obesity based on a BMI of 30 or greater roughly doubled during the same period, from about 1 in 10 to 1 in 5. The prevalence of clinically severe obesity is increasing much faster than obesity. The widely published trends for overweight/obesity underestimate the consequences for physician practices, hospitals, and health plans because comorbidities and resulting service use are much higher among severely obese individuals. Accommodating severely obese patients will no longer be a rare event, and providers have to prepare to treat such patients on a regular basis.