Youfa Wang, MD, PhD, and Xiaoli Chen, MD, PhD, both from the Johns Hopkins Bloomberg School of Public Health, Baltimore, Maryland wrote that, "Different from what we expected, few of the racial/ethnic differences in diet, exercise, and weight status were explained by health- and nutrition-related psychosocial factors. But SES explained a considerable portion of the disparities."
Specifically, SES explained 30% of the black-white difference in dietary quality, and about 40% of the difference in obesity.
Initially, the researchers hypothesized that between-group differences in nutrition and health-related psychosocial factors (NHRPF) underlie the large racial/ethnic differences in dietary intake, exercise, and obesity among adults.
To test the hypothesis, they analyzed data from 4356 healthy individuals aged 20 to 65 years who participated in the US Department of Agriculture (USDA)'s 1994 to 1996 Continuing Survey of Food Intakes by Individuals, and who had completed the Diet and Health Knowledge Survey.
That survey probed nutritional intake, awareness of the links between diet and health, and NHRPF. For example, 6 questions asked participants to identify factors that were important to them when selecting foods, including taste, safety, ease of preparation, freshness, nutrition, and price. The investigators evaluated awareness of nutrition-related health risks by asking for a "yes" or "no" answer to whether participants had heard about specific examples, such as danger of eating too much sugar or not enough fiber. Education level and household income were used to describe SES.
Overall, Hispanics scored higher on the USDA Healthy Eating Index (HEI) than did non-Hispanics. Non-Hispanic blacks had lower HEI scores and higher body mass than non-Hispanic whites and were less likely to exercise.
After controlling for NHRPF, the ethnic and racial differences in body mass index and diet were unaffected. However, with adjustment for SES, the differences between Hispanics and whites increased, whereas the black-white differences in HEI decreased.
"The underlying causes of ethnic disparities in health-related behaviors such as eating and exercise and obesity in the United States are complicated," the authors conclude. "More well-designed studies...are needed to help advance the understanding.... Such knowledge is needed to help develop evidence-based national policies and programs to eliminate health disparities."
J Am Diet Assoc. 2011;111:1904-1911