The relative contributions of different levels of overweight and obesity to the increased prevalence of diabetes in the United States: 1976-2004.

BACKGROUND: Policy makers are divided on whether to focus public health efforts to prevent type 2 diabetes on subpopulations at high risk or on the entire population. We examined the extent to which increases in the prevalence of overweight, obesity, and severe obesity have contributed to the increase in diabetes prevalence among U.S. adults between 1976-1980 and 1999-2004.
METHODS: Using assembled data of 37,606 U.S. adults aged 20 to 74 years from 3 consecutive U.S. national surveys (NHANES II, III, and NHANES 1999-2004), we compared the body mass index distributions among prevalent diabetes cases over time and divided changes in prevalence of 5 diabetes-body mass index categories by changes in the diabetes prevalence observed in the total population.
RESULTS: Prevalence of diabetes among adults aged 20 to 74 increased from 5.08% in 1976-1980 to 8.83% in 1999-2004. Of the 3.75 additional cases per hundred that existed in 1999-2004 as compared to 1976-1980, we estimated that -8% were among persons of normal or below normal weight (body mass index<25); 27% were among those who were overweight (body mass index 25 to 30); and 32%, 23%, and 26% among those with class I (body mass index 30 to 35), class II (body mass index 35 to 40), and class III obesity (body mass index>40), respectively. Thus, of the additional prevalent diabetes cases that existed in 1999-2004 as compared to 1976-1980, 81% were obese (i.e. body mass index>30) and 49% had class II or III obesity (body mass index>35), a group that increased in prevalence from 4% to 13% of the overall adult population.
CONCLUSIONS: The increases in diabetes prevalence over recent decades have been disproportionately comprised of persons with extreme levels of obesity.