Gallup: US obesity rate climbing in 2013 for almost all demographic groups

The adult obesity rate in the United States so far in 2013 is 27.2%, up from 26.2% in 2012, and is on pace to surpass all annual average obesity rates since Gallup-Healthways began tracking in 2008.

The one-percentage-point uptick in the obesity rate so far in 2013 is statistically significant and is the largest year-over-year increase since 2009. The higher rate thus far in 2013 reverses the lower levels recorded in 2011 and 2012, and is much higher than the 25.5% who were obese in 2008.

The increase in obesity rate is accompanied by a slight decline in the percentage of Americans classified as normal weight or as overweight but not obese. The percentage of normal weight adults fell to 35.3% from 35.9% in 2012, while the percentage of adults who are overweight declined to 35.5% from 36.1% in 2012. An additional 1.9% of Americans are classified as underweight in 2013 so far.

Since 2011, U.S. adults have been about as likely to be classified as overweight as normal weight. Prior to that, Americans were most commonly classified as overweight.

Gallup and Healthways began tracking Americans' weight in 2008. The 2013 data are based on more than 141,000 interviews conducted from Jan. 1 through Oct. 28 as part of the Gallup-Healthways Well-Being Index. Gallup uses respondents' self-reported height and weight to calculate body mass index (BMI) scores. Individual BMI values of 30 or above are classified as "obese,"25 to 29.9 are "overweight,"18.5 to 24.9 are "normal weight,"and 18.4 or less are "underweight."