April 16, 2014

Study: Oft-assumed reasons for racial obesity disparities may not be only cause

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racial disparities obesityRacial disparities in obesity rates among the third of U.S. adults considered obese are often blamed on socioeconomic status because of its influence on diet and physical activity, but new findings from the University of Alabama at Birmingham published in Obesity suggest otherwise — particularly for women.

Non-Hispanic blacks in the United States have the highest age-adjusted rates of obesity at 47.8 percent, while the rate for non-Hispanic whites is at 32.6 percent, according to the Centers for Disease Control and Prevention.

Bisakha Sen, Ph.D., associate professor of health care policy at UAB, used health behavior data for whites and blacks from Alabama and Mississippi taken from the national Behavioral Risk Factor Surveillance System and took a method used in economics to analyze gender wage disparities. Her team applied the Oaxaca-Blinder decomposition to health disparities to determine how much they could be explained by differences in factors like socioeconomic status, diet and physical activity levels.

“Data show that African-Americans have higher body mass indexes than do whites, and as a group, they have lower income and education levels, consume less fruits and vegetables, and work out less,” Sen said. “The method we used allowed us to create a hypothetical world where these measured things are, on average, exactly the same for blacks as they are for whites, letting us analyze these factors’ effect on obesity disparities.”

Sen says their method shows that, when the variable disparities are taken away, the BMI for black men would actually be similar to that of white men, so these variables do explain disparities in obesity levels among men.

Sen was surprised, though, that more similar findings were not present in women. Without the variable disparities in women, only 10 percent of the differences in white and black females could be explained.

“It’s pretty well-known that disparities in obesity are more in women than in men, but I thought surely we would get rid of 50 percent of the disparity, not just 10,” Sen said. “So while we think we know what matters — socioeconomic status, fruit and vegetable intake, physical activity level — these actually matter very little in explaining racial disparities among women.”

Without the typically assumed variables as the cause of obesity disparities in women, Sen says other factors like culture or genetics could be to blame, but more scientific studies are needed.

Because the findings are based on data only from people living in Mississippi and Alabama, Sen says it cannot yet be generalized for all people in the United States. However, she does suggest that policymakers should take note.

“Right now, many are focusing energy making sure minorities get enough fruits and vegetables,” Sen said. “Our findings suggest you can get African-Americans to consume the same level that whites do, and — while it appears to work for men — it won’t do very much in women. Let’s start thinking of what we’re not thinking of when collecting big data sets like BRFSS: What do we need to be asking, and what else could be affecting racial disparities in obesity that we aren’t looking at already?”