Causes of rising obesity in U.S. often incorrect

General notions about the causes of obesity in the United States could be wrong, according to new analysis published in CA: Cancer Journal for Clinicians.

“Many factors have been suggested as causes. Fast food, time spent viewing television or looking at computer screens, increasing portion sizes, poverty and even supermarket availability are blamed,” Ruopeng An, PhD, kinesiology and community health professor at the University of Illinois, and conductor of the study stated in a news release. “As it turns out, some widely held beliefs about societal trends are unambiguously false; others require some qualifications.”

The researchers showed that while disparities exist among various groups, most economic, educational and ethnic groups have seen their obesity levels increase at similar rates over time.

Geography and the existence of regions with limited access to affordable, healthy food appear to have little bearing on the obesity trend in general, although they may be linked to differences between groups at any given point in time, An said.

“A common misbelief is that the obesity epidemic reflects increasing social disparities and that the largest weight gains are concentrated in groups identifiable by race, ethnicity, income, education or geography,” he said. “And it is true that if you look at the national data for any one point in time, it is not hard to figure out, for example, that the people with the lowest education tend to have the highest obesity rate. Everyone buys this argument. But what is less obvious is how surprisingly similar the obesity trend is for all groups.”

A look at graphs of obesity over time offers a more universal view of what is going on, An said. Obesity is higher for blacks than for whites, but both groups are getting heavier at almost the same rate over time. The same disparity is seen in people who never finished high school vs. college graduates or people with lower vs. higher incomes, An said.

“The gap between groups is secondary to the increase that all groups experience over time,” he said. “So a reversal of the obesity epidemic would need universal intuitions rather than a focus on certain groups.”

For more information:

An R. CA Cancer J Clin. 2014:doi:10.3322/caac.21237

Disclosure: Funding provided by the National Institutes of Health and RAND internal funds. The authors report no conflicts of interest.

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