Socioeconomic inequality of obesity in the United States: do gender, age, and ethnicity matter?

This study introduces the concentration index (CI) to assess socioeconomic inequality in the distribution of obesity among American adults aged 18–60 years old. The CI provides a summary measure of socioeconomic inequality, and enabled comparisons across gender, age, and ethnicity. Data from the National Health and Nutrition Examination Survey III, 1988–1994 (NHANES III) were used. The degree of socioeconomic inequality in obesity varied considerably across gender, age, and ethnic groups. Among women, we found a stronger, inverse association between socioeconomic status (SES) and obesity compared with men, as well as greater socioeconomic inequality among middle-aged adults (41–49) compared to other age groups. Consistent with previous studies, we found remarkable ethnic differences in the relationship between SES and obesity. Although the extant literature documented a higher prevalence of obesity among minorities than in whites, our results presented a lower socioeconomic inequality in obesity within minority groups. Our analyses suggested that gender, age, and ethnicity could be important factors on socioeconomic inequality in obesity.