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Childhood obesity drops 40 percent in the past 10 years, or perhaps not

Media reports have distorted research findings on obesity rates.
Media reports have distorted research findings on obesity rates.
Photo by Al Bello/Getty Images

Science and medicine journal PLOS published a blog entry Monday slamming extensive media coverage of research indicating that childhood obesity has dropped by 40 percent in the past decade - a number that, while technically correct for one particular age group, distorts the study's actual findings.

The study, published in the Journal of the American Medical Association (JAMA), used CDC National Health and Nutrition Examination Survey data to compare obesity rates among children and adults from 2003-2004 and 2011-2012.

In the blog article, writer and Ph.D. candidate Atif Kukaswadia quotes the portion of the study that most press accounts jumped on: “There was a significant decrease in obesity among 2- to 5-year-old children (from 13.9 percent to 8.4 percent).”

Instead of reporting the 5.5 percentage point absolute difference, says Kukaswadia, reporters ran with the relative difference, 40 percent.

Headlines trumpeted supposed dramatic drops in childhood obesity, with some going so far as to call the childhood obesity epidemic a myth perpetuated by health activists like Michelle Obama.

Meanwhile, the CDC warns that the number of obese children has more than doubled in the past 30 years, and the number of obese adolescents has quadrupled. The agency says that in 2012, more than one third of children and adolescents were overweight or obese.

While children between the ages of two and five years showed a decrease in obesity of 5.5 percentage points in the JAMA article, the research found no decrease among the group encompassing children ages 2 through 19.

The researchers conclude, "Overall, there have been no significant changes in obesity prevalence in youth or adults between 2003-2004 and 2011-2012. Obesity prevalence remains high and thus it is important to continue surveillance."

Kukaswadia writes,"This makes me wonder how many journalists read the article, how many got to the end, and how many just saw what other people had reported and ran with the same headline and narrative."