Objective To monitor trends in state-specific data and to examine changes in the prevalence of obesity among adults.

Design Cross-sectional random-digit telephone survey (Behavioral Risk Factor Surveillance System) of noninstitutionalized adults aged 18 years or older conducted by the Centers for Disease Control and Prevention and state health departments from 1991 to 1998.

Setting States that participated in the Behavioral Risk Factor Surveillance System.

Main Outcome Measures Body mass index calculated from self-reported weight and height.

Results The prevalence of obesity (defined as a body mass index greater than or equal to 30 kg/m(2)) increased from 12.0% in 1991 to 17.9% in 1998. A steady increase was observed in all states; in both sexes; across age groups, races, educational levels; and occurred regardless of smoking status. The greatest magnitude of increase was found in the following groups: 18- to 29-year-olds (7.1% to 12.1%), those with some college education (10.6% to 17.8%), and those of Hispanic ethnicity (11.6% to 20.8%), The magnitude of the increased prevalence varied by region (ranging from 31.9% for mid Atlantic to 67.2% for South Atlantic, the area with the greatest increases) and by state (ranging from 11.3% for Delaware to 101.8% for Georgia, the state with the greatest increases).

Conclusions Obesity continues to increase rapidly in the United States. To alter this trend, strategies and programs for weight maintenance as well as weight reduction must become a higher public health priority.