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.
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.”
Obesity Rates Increase Across Almost All Demographic Groups
Obesity rates have increased at least slightly so far in 2013 across almost all major demographic and socioeconomic groups. One exception is 18- to 29-year-olds, among whom the percentage who are obese has remained stable. The largest upticks between 2012 and 2013 were among those aged 45 to 64 and those who earn between $30,000 and $74,999 annually. The obesity rate within both groups increased by 1.8 points, which exceeds the one-point increase in the national average.
At 35.7%, blacks continue to be the demographic group most likely to be obese, while those aged 18 to 29 and those who earn over $75,000 annually continue to be the least likely to be obese.
Percentage Obese in U.S. Among Demographic Groups
From this data, An believes it is too early to conclude that the prevalence of obesity has begun to level off or even decrease in the United States.
“We can’t be naive and underestimate the severity of the obesity epidemic in the U.S. Although there is some preliminary evidence about the decline of obesity prevalence among low income preschoolers, that population is unique; we haven’t gotten good measures for the entire child or adolescent population,” An said. “For the adult population, there are minor declines in the overweight and obesity rate if we compare data from 2012 to that in 2010, but the declines are very small and statistically insignificant. We cannot rule out the hypothesis that the prevalence of obesity follows the same trend as in the last decade.”
An suggests scientists continue their close monitoring of the obesity trend in the U.S. so they can find a solution that will decrease the rate of those suffering from this costly health epidemic.
“People are quite creative and there are many proposals being raised for the situation, but nevertheless, we haven’t seen any large-scale health policy intervention that is effective in reducing the obesity rate among the population,” An said. “We still have a long way to go in order to reduce obesity prevalence.”
Chelsey B. Coombs
University of Illinois at Urbana-Champaign