New evidence shows increase in obesity may be slowing, but not by much

In his 2014 State of the Union address, President Barack Obama referred to an August 2013 Centers for Disease Control and Prevention study that showed a decline in the obesity rate among low-income pre-school children, saying, "Michelle's Let's Move! partnership with schools, businesses and local leaders has helped bring down childhood obesity rates for the first time in 30 years, and that's an achievement that will improve lives and reduce health care costs for decades to come."

While the CDC report's data is encouraging, a new study published by University of Illinois kinesiology and community health professor Ruopeng An shows the notion that the American obesity epidemic has begun to reverse may be premature.

The study appears in the journal ISRN Obesity.

An said that when the CDC released the report showing declines in obesity among low-income preschool children in 19 of 43 states, it "immediately received a tremendous amount of media attention."

"Because people have been fighting the obesity epidemic since the 1980s, this data really looked like a promising sign," An said. "This triggered my research because I was curious as to whether a similar trend is happening in the adult population."

An turned to the National Health and Nutrition Examination Survey (NHANES) to gather his data. The CDC conducts this nationally representative survey of 5,000 people 20 years of age and older each year, visiting residential areas in a mobile test center. Researchers and physicians examine the participants, collecting objective data such as their height and weight, as well as other health-related statistics.

When An examined the Body Mass Index measurements (or BMI, calculated by dividing a person's weight by his or her height), he found that 71.1 percent of men and 65.6 percent of women in the 2011-2012 NHANES study sample had BMIs greater than or equal to 25, meaning they were overweight or obese. When he compared these levels to those from 2000, he noticed something interesting.

"Starting from 2000, the increase in the rate of the prevalence of adult obesity is slowing, but the prevalence is still increasing, especially in those with a BMI higher than 35," An said. "If you look at those with a BMI greater than 25 - the cutoff point for being overweight - this prevalence only increases slightly over the last 12 years. But those with a BMI greater than 40 - those who are morbidly obese – had the greatest increase in rate compared to the baseline in 2000."

The adult obesity rate 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.