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.