Socioeconomic status may explain racial disparities in diet, exercise, and weight

Large disparities exist in obesity and other chronic diseases across racial/ethnic groups in the United States. Are racial differences in diet, exercise, and weight status related to better knowledge about healthy eating and awareness of food-related health risks? Or are they more closely related to differences in socioeconomic status (SES)? A new study published in the December issue of the Journal of the American Dietetic Association finds that people with a lower socioeconomic status are more likely to be overweight, regardless of racial/ethnic background, and that the level of nutritional knowledge and health awareness did not lead to significant racial differences in weight and diet.

"Our findings suggest that disparities in obesity in the United States may be more affected by the broader social environment," said authors Youfa Wang, MD, PhD, MS, director of the Johns Hopkins Global Center for Childhood Obesity and associate professor of International Health and Epidemiology, and Xialoi Chen, MD, PhD, MPH, assistant scientist in the Department of International Health at Johns Hopkins Bloomberg School of Public Health, Baltimore, MD. "Poor quality retail food environments in disadvantaged neighborhoods, in conjunction with limited individual economic resources, contribute to increased risk of obesity within ethnic minorities and socioeconomically disadvantaged populations."

The authors hypothesized that between-group differences in nutrition- and health-related psychosocial factors, including nutrition knowledge and beliefs, are important contributors to the large racial/ethnic and socioeconomic differences observed in U.S. adults' dietary intakes, exercise, and obesity. They analyzed nationally representative data collected from 4,356 individuals who had participated in the U.S. Department of Agriculture's Continuing Survey of Individual Food Intakes, and who had completed the Diet and Health Knowledge Survey, which asks about self-perceptions of nutritional intake, awareness of the relationship between diet and health, perceived importance of following nutritional guidelines, and other questions related to health and diet.

Each participant was asked 24 questions to evaluate nutrition and health-related psychosocial factors (NHRPF). SES was assessed using education and household income. The authors analyzed the relationship between NHRPF and SES with self-reported dietary intake, diet quality (measured by the U.S. Department of Agriculture's Healthy Eating Index [HEI]), exercise participation, body mass index (BMI), and overweight or obesity. Changes in racial/ethnic differences in weight status were compared with diet and exercise participation.

In general, compared to non-Hispanic whites, non-Hispanic blacks had higher BMI and scored lower on the HEI, and were less likely to participate in exercise. Hispanics scored higher on the HEI. The racial and ethnic differences in diet and BMI changed little after controlling for NHRPF. But when SES was controlled for, the black–white differences in HEI became smaller and the white–Hispanic differences became greater.

"Our study shows several important findings that could help enhance the understanding of the complex factors that affect disparities in diet, exercise, and obesity across ethnic and SES groups," commented Dr. Wang. "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."

"The underlying causes of ethnic disparities in eating, exercise, and obesity in the United States are complicated. More well-designed studies with vigorous and comprehensive assessment of related factors are needed to help advance understanding."