Gallup survey: All U.S. age groups are fatter than four years ago WASHINGTON, Oct. 27 (UPI) -- U.S. adults in all age groups have grown fatter during the past four years, a survey indicated. The Gallup-Healthways Well-Being Index -- conducted from Jan. 2 to Dec. 31, 2008, and from Jan. 2 to Sept. 30, 2012 -- included interviews with 579,210 U.S. adults age 18 and older. Gallup calculated the survey respondents' body mass indices using the standard formula based on their self-reported height and weight. The overall adult obesity rate was 26.1 percent in 2012 versus 25.5 in 2008, the survey said. Obesity increases as Americans at both genders get older before declining when they reach their early 70s. The youngest of adults ages 18-to-23 and 24-to-27 had minimal increased in obesity. However, most U.S. adults age 35 and older are more likely to be obese than those who were at the same age four years ago. The age group with the most obesity was 56-59 in 2012 at 31.7 percent, and the age group with the least obesity was age 88 and older. In 2008, those ages 64-69 were the most obese at 30.8 percent and the least obese were those age 88 and older at 9.4 percent. For the overall survey, the margin of error was 1 percentage point, but the margin of error was 1.5 percentage points for each age group.