Awareness of obesity has existed since the Stone Age,2 and there are numerous references to obesity in Hippocratic writings.3 Throughout history, obesity has occurred most commonly in the upper socioeconomic strata, but increased weight in the past did not usually approach the level currently categorized as extreme obesity. Until the last 45 years, population data sets that could estimate the prevalence of extreme obesity in the United States did not exist.
Two large-scale national data sets have tracked the prevalence of obesity in the United States, the National Health and Nutrition Examination Survey (NHANES) and the Behavioral Risk Factor Surveillance System (BRFSS).4 The NHANES obtains measured data on height and weight in a representative sample of the US noninstitutionalized civilian population. The BRFSS is a multistage survey that obtains self-reported data on height and weight from individuals in each state with use of random-digit dialing. Because data from the BRFSS are obtained by self-report, it likely underestimates the true prevalence of obesity. Moreover, underreporting increases with the magnitude of overweight.5 Nonetheless, the BRFSS is useful for following national trends over time.
According to the BRFSS, the prevalence of extreme obesity has been increasing twice as fast as obesity in general.6 Data from the BRFSS have been summarized for the period from 1990 to 2000.7 During this decade, the overall prevalence of extreme obesity increased almost 3-fold, from 0.8% to 2.2%, and this increase was seen in both sexes, all racial/ethnic groups, all age groups, and all education levels. The prevalence of extreme obesity was greater among blacks than among non-Hispanic whites or Hispanics, greater among persons who did not complete high school, greater among shorter than among taller persons, and approximately 2-fold greater among women than among men. The largest proportional increase among age groups was seen in 18- to 29-year-olds. The higher the BMI at baseline, the greater the increase in BMI, ie, the heaviest people gained the most weight.
The NHANES has tracked BMI data since NHANES I was conducted in 1960-1962, at which time the prevalence of obesity was 13.4%.8 From NHANES II in 1976-1980 to NHANES III in 1988-1994, the prevalence of obesity increased from 15.0% to 23.3%. The latest data from the NHANES showed that in 2003-2004, 66.3% of adult (>=20 years) Americans were overweight or obese, and 32.2% were obese.9 Compared to the period 1999-2000, the prevalence of obesity in 2003-2004 was stable among women (33.4% and 33.2%, respectively) but increased among men (from 27.5% to
The NHANES found a 2.9% prevalence of extreme obesity in 1988-1994, 4.7% in 1999-2000, and 4.8% in 2003-2004.8,9 Although the overall prevalence of extreme obesity was stable between 1999-2000 and 2003-2004 and affects almost 1 in 20 Americans overall, it appeared to be increasing in the 20- to 39-year age group (5.4% in 2003-2004 compared with 4.5% in 1999). In 2003-2004, the prevalence of extreme obesity was greater among women (6.9%) than among men (2.8%), greater among blacks (10.5%) than among non-Hispanic whites (4.3%) or Hispanics (4.5%), and highest among black women (14.7%).