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Teen-obesity epidemic has plateaued — but not among the poor

person in gym
REUTERS/Rick Wilking
A study published earlier this week reports that there is “a significant and growing” obesity gap between teens from upper and lower socioeconomic backgrounds.

We’ve had some (mildly) good news about obesity in recent months. Studies have suggested that the obesity rate among U.S. children and teens has begun to plateau. Other research has found that young people in the U.S. are consuming fewer daily calories than they did a decade ago, especially calories from sugar and other carbohydrates. The percentages are small (7 percent fewer calories among boys and 4 percent fewer among girls) but significant nevertheless.

In addition, the consumption of fast food is on the decline, and children are, on average, more physically active that they were in the late 1990s.

And yet, all those positive advances in the public-health fight against the childhood obesity “epidemic” may be masking a very troubling trend. For a study published earlier this week reports that there is “a significant and growing” obesity gap between teens from upper and lower socioeconomic backgrounds.

Two surveys, similar results

For the study, a team of Harvard University researchers used data from two nationally represented health surveys, the 1988-2010 National Health and Nutrition Examination Surveys and the 2003-2011 National Survey of Children’s Health.

Like other researchers, they found no change in the prevalence of obesity among teens aged 12 to 17 between 2003-2004 and 2009-2010 — more evidence that the rapid obesity increases of the 1980s and 1990s are leveling off.

But when the researchers looked at the data by parental education, they found a startling difference: Obesity has been decreasing among teenagers whose parents have at least a four-year college degree — by 7 percent in one of the surveys and by 11 percent in the other. But at the same time, obesity has been increasing — by 26 and 29 percent, depending on the survey — for teenagers whose parents have at most a high school education.

The researchers found similar trends when they used family income instead of parental education to measure socioeconomic status.

Race and ethnicity did not seem to be a factor, however. In fact, “the divergence was even greater among non-Hispanic whites than it was for the entire sample,” the researchers write.

Limited food choices

To try to figure out what is behind these socioeconomic differences, the researchers looked at behaviors related to calorie intake and physical activity.

They found that the daily calorie intake of all children decreased during the 12 years of the study. That intake fell more among the children of the wealthier, college-educated parents, but there was a surprise: By 2010, the poorer teens were actually consuming fewer calories, on average, than their more affluent peers.

So why would their obesity rate be higher? Perhaps, speculated the researchers, because more of their calories were coming from processed and/or fast foods.

“Not only are fresh vegetables and fruits costlier than fast food, but healthy alternatives are sometimes hard to find in poor neighborhoods,” explain the authors of the study. “According to a recent estimate by the US Department of Agriculture, 9.7% of the US population, or 29.7 million people, live in low-income areas more than one mile from a supermarket, where the only options for grocery shopping are ‘convenience’ stores, liquor stores, gas stations, or fast food restaurants that sell foods high in fat, sugar and salt.”

“Low-income families are less likely to own a car, and may thus opt for diets that are shelf-stable,” the researchers add. “Dry packaged foods have a long shelf life, but they also contain refined grains, added sugars, and added fats.”

Less exercise opportunities

Still, differences in physical activity are a much more likely reason for the growing class disparity in the teen obesity rates, say the researchers. Their analysis of the data revealed that the children of college-educated parents are more physically active than they were a decade ago. No such increase in physical activity was found among the children of less educated parents.

“This could be because many low [socioeconomic] children live in environments that do not facilitate a physically active lifestyle,” write the researchers. “The lack of community recreational centers, playgrounds, or sidewalks and concerns for safety when outdoors can stand in the way of children being physically active. However, although neighborhood constraints may contribute to differences in physical activity, this is not the full story: Participation in high school sports and clubs has increased among high [socioeconomic] adolescents while decreasing among their low [socioeconomic] peers.”

‘More vigorous support’

The authors of the study call for additional research into the causes of health inequalities related to obesity and “more vigorous government support and targeted programs” to help fight obesity.

“Effective intervention programs to promote healthy lifestyles among young people (especially among lower [socioeconomic] youth) will not only aid in the fight against the youth obesity epidemic,” they point out, “but will help prevent other chronic diseases, reduce future health care costs, and pave the way for a healthier nation.”

The study was published this week in the Proceedings of the National Academy of Sciences.

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