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Drop or No Drop? What Those Confusing Obesity Stats Really Mean


When the U.S. Centers for Disease Control and Prevention (CDC) released a study in February showing a stunning 43 percent drop in the obesity rates among preschoolers, it was an exciting moment for advocates in the fight to reverse childhood obesity. But a follow-up study conducted by other researchers seemed to come to different conclusions, leading to some confusion.

The Inside Track’s Donna Brutkoski spoke with Sally Wong PhD RD CDN, Associate Science and Medicine Advisor at the American Heart Association, to get a better idea of what all these numbers really mean. Although there’s still some cause for optimism, Wong notes that the focus needs to remain on a troubling trend in the fight against childhood obesity.

Where are the data to analyze childhood obesity rates drawn from?

The data for both studies were drawn from the National Health and Nutrition Examination Survey (NHANES), an ongoing long-term program that assesses the health and nutrition status of both adults and children in the U.S. Although both studies used the NHANES dataset, Skinner and Skelton looked at a 14 year period from 1999 to 2012 and found that while childhood obesity rate may have leveled off with no significant increases for children 2- to 19-years-old since 2009-2010, the rate of severe obesity increased especially in Hispanic girls and Black boys.

The media originally zeroed in on one particular number in the CDC study on childhood obesity published in February. What was the significance there?

A dramatic 43 percent drop in obesity rates in children ages 2- to 5-years-old between the years 2003 to 2012 was reported in February in a separate analysis of data taken from NHANES. It should be noted that this age group is a small sample in the overall study. While some states and communities are showing signs of progress to help these national numbers stabilize, until we see major shifts towards downward trends, we look to community leaders to set aggressive goals to support a culture of health.

A follow-up study published in the JAMA Pediatrics journal in April looked at the data in a different way and didn’t find the same decrease. How would you explain the differences?

The idea that obesity rates were plunging among preschoolers, as heralded in the study and press release from the CDC, did not stand up when researchers scrutinized a few extra years of data. This later study did find that the overall childhood obesity rate, in children ages 2 to 19, has leveled off, with no significant increases since 2010. But it should also be noted that the leveling off could partially be attributed to the increased numbers of children who are severely obese and no longer included in the overweight or less severely obese categories.

Another trend researchers found in the data is of much larger concern to you and the American Heart Association, right?

Yes. Skinner and Skelton found in their study that while obesity rates are leveling off for whites and for our nation’s youngest children, rates remain high for blacks, Hispanics and older children, especially rates of severe obesity.

  • Hispanic females’ rates of overweight increased from 31.7% to 38.3%, obesity climbed from 15.7 percent to 20.4 percent and class 2 (severe) obesity more than doubled from 3.2 percent to 7.3 percent over the 14-year period.
  • Black males’ rates of overweight rose from 30.7 percent to 34.3 percent, obesity increased from 17 percent to 19.8 percent and class 2 (severe) obesity grew from 6.1 percent to 10.1 percent over the 14-year period.

What does “severe obesity” mean?

Severe obesity is a relatively new term that the American Heart association has published in its Scientific Statement in 2013. Severe obesity for children is defined as a Body Mass Index greater than 120 percent of the 95th percentile for age and sex or a Body Mass Index of 35 or greater, whichever is lower.

The studies agreed that the overall rate of childhood obesity has continued to level off. Is that good news?

While declines are in sight among young children, the rate of severe obesity is still on the rise among teenagers. Addressing severe obesity is critical to the long-term health of children in the U.S., especially because obesity and severe obesity in adults is expected to increase significantly until 2030.

In the bigger picture, what do all these numbers mean for advocates battling childhood obesity?

This study underscores the need to focus our efforts with Voices for Healthy Kids®, an initiative of the American Heart Association and Robert Wood Johnson Foundation working to reverse the childhood obesity epidemic by 2015, to increase access to healthy foods and safe places to play in minority communities and priority populations. The American Heart Association is actively supporting communities across the country as they strive to gain better access to fruits and vegetables, build more parks and pedestrian-friendly streets and support schools and families as the core of a healthy community.