Illustrating a "consequential" Shift in the Study of Health Inequalities: A decomposition of Racial Differences in the Distribution of Body Mass

Purpose: We present a conceptual introduction to "distributional inequalities"-differences in distributions of risk factors or other outcomes between social groups-as a consequential shift for research on health inequalities. We also review a companion analytical methodology, "distributional decomposition", which can assess the population characteristics that explain distributional inequalities.

Methods: Using the 1999-2012 U.S. National Health and Nutrition Examination Survey, we apply statistical decomposition to (a) document gender-specific, black-white inequalities in the distribution of body mass index (BMI) and, (b) assess the extent to which demographic (age), socioeconomic (family income, education), and behavioral predictors (caloric intake, physical activity, smoking, alcohol consumption) are associated with broader distributional inequalities in BMI.

Results: Black people demonstrate favorable or no different caloric intake, smoking, or alcohol consumption than whites, but worse levels of physical activity. Racial inequalities extend beyond the obesity threshold to the broader BMI distribution. Demographic, socioeconomic, and behavioral characteristics jointly explain more of the distributional inequality among men than women.

Conclusions: Black-white distributional inequalities are present both among men and women, although the mechanisms may differ by gender. The notion of "distributional inequalities" offers an additional purchase for studying social inequalities in health.