The Gallup-Healthways Well-Being Index 2012 was comprised of more than 350,000 surveys of U.S. adults who self-reported their height and weight to calculate body mass index scores.
Individual BMI values of 30 or above were classified as obese; 25 to 29.9 were overweight; 18.5 to 24.9 were normal weight and 18.4 or less were underweight. Those with BMI of 40 or higher were considered morbidly obese.
Based on the self-reports, 3.6 percent of U.S. adults were morbidly obese last year, on par with 3.4 percent in 2011 and 3.5 percent in 2009 and 2010, Gallup said.
he percentage of Americans who were obese in all major demographic and socioeconomic groups stayed about the same in 2012 compared with 2011.
Blacks, people ages 45-64 and low-income Americans were the most likely to be classified as obese, as has been the case since 2008. Those ages 18-29 and higher-income Americans were the least likely to be obese, Gallup said.
The telephone interviews were conducted Jan. 1-Dec. 31, 2012. The margin of error overall was 0.2 percentage points, while subgroups had a margin of error of 1 percentage point.