Uncovering the real drivers of obesity in young people

A comparison of obesity rates among 12- to 17-year-olds by parental education. Panel A is data from National Health and Nutrition Examination Surveys and B is from National Survey of Children’s Health. BA = bachelor’s degree, HS = high school. Source: Increasing socioeconomic disparities in adolescent obesity, PNAS (2014).

It’s great that the rapid rise in youth obesity since the 1980s has started to level off. But there’s an unsettling trend hidden in the data: Progress has largely been limited to kids from more educated and higher income families, according to a recent analysis that got less news coverage than it should have.

Robert Putnam and colleagues at the Harvard Kennedy School compared outcomes by education and income using data from two nationally representative health surveys (the 1988–2010 National Health and Nutrition Examination Surveys and the 2003–2011 National Survey of Children’s Health).

Among teenage children of parents with a college degree, they found that the prevalence of obesity began to drop about 10 years ago, while it continued to climb among the teenagers of parents who have at most a high school degree. They found the same trend when they used estimates of family income, rather than education, to measure socioeconomic status. (The growing gap is not merely a reflection of racial or ethnic differences, they say, because it persisted even when they limited the analysis to non-Hispanic whites.)

Physical activity – or the lack of it – emerged as a key factor in the worsening gap, according to the researchers. Average daily calorie intake declined across the board, but not much differently by education or income. Exercise habits diverged significantly. Children of college-educated parents became more active than they were a decade ago, while children of less educated parents showed no improvement.

Why this is so remains a mystery. Putnam and co-authors mention one intriguing fact: Participation in high school sports and clubs has decreased among kids from lower socioeconomic households, while it has increased among those higher up on the education/income ladder. I’d love to see more reporting on this.

It’s become conventional wisdom to say that low-income neighborhoods are a barrier to being physically active because they aren’t safe and lack parks, recreational centers, walking trails, etc. But the evidence for that is weak, and some findings suggest to me that yet-to-be nailed down sociocultural factors may be much more important… [Continue reading at HealthJournalism.org]

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