Child Obesity Declines, but is Data Overblown?

Over the past few days the headlines have all read some variation of “childhood obesity plummets!” Unfortunately, the reality is this is not only a slight exaggeration, but the decrease in obesity was only reported for a very small segment of children.

In the February 26 issue of JAMA the Centers for Disease Control (CDC) published obesity data that showed a significant decline in obesity among children ages 2 to 5. In 2003-2004 the obesity rate among this age group was 14% and in 2011-2012 it was reported at just over 8%--a decline of 43%.

“We continue to see signs that, for some children in this country, the scales are tipping,” CDC Director Tom Frieden, MD, MPH, said in a statement. “This report comes on the heels of previous CDC data that found a significant decline in obesity prevalence among low-income children aged 2 to 4 years participating in federal nutrition programs.”

Geoffrey Kabat of Forbes was quick to judge the data and the press release from the CDC, writing:

“If one calculates the percent decline from 2003-2004 to 2009-2010 — rather than for the period 2003-2004 to 2011-2012 – one obtains a much less impressive 14 percent rather than 43 percent. In fact, researchers who use survey data like those presented in the JAMA paper are well aware that there are chance fluctuations in such data, and they are generally wary of seizing on short-term changes within subgroups.”

The study examined five times: 2003-2004, 2005-2006, 2007-2008, 2009-2010, and 2011-2012. After 2003-2004 the obesity rate declined to 10.7%, then 10.2%, before increasing to 12.2% in 2009-2010. The authors even mention in the paper that “the selection of the initial point can have an effect on the findings.”

While there is no denying that the obesity epidemic among young children has reversed—even if the exact percentage can be debated—the data isn’t as positive for adults. The report in JAMA did state that there have been “no significant changes” in obesity prevalence among 2- to 19-year-olds or adults. Nearly 18% of children between the age of 6 and 11 are still obese, as well as 20.5% of those aged 12 to 19.

Gallup released its own poll just a day later that revealed the percentage of morbidly obese rose slightly to 3.8% (a new high) and obesity overall also increased to 27.1% in 2013. The Gallup poll uses respondents’ self-reports of height and weight, while the National Health and Nutrition Examination Study (NHNES), which the CDC used, based BMI scores on the heights and weights in clinical measurements. As such, the NHNES placed the country’s obesity rate even higher at 34.9%

According to Gallup, for the last six years nearly two-thirds of Americans have had BMIs higher than recommended and roughly 35% were in the normal weight category.

The obesity rate among 45- to 64-year-olds increased the most from 30.7% in 2012 to 32.5% in 2013. Meanwhile those between the ages of 18 and 29 reported no overall change in the obesity rate (17.2%).

“Some of the groups with the highest obesity rates saw the largest increases from 2012 to 2013,” according to Gallup. “The obesity rate increased by more than one point among Americans who make less than $36,000 a year, 45- to 64-year-olds, and those living in the South.”

Gallup points out that previous polls revealed that Americans’ eating habits worsened in 2013 and they were exercising less in the first half of the year, which may have contributed to the increase in obesity.

“Though the rate of childhood obesity—which the Gallup-Healthways Well-Being Index does not track—has dropped over the last decade, it is yet to be seen whether it will lead to lower adult obesity rates in the years to come,” Gallup reported.