The Relationship of Socioeconomic Status with Body Mass Index Depends on the Socioeconomic Measure Used

OBJECTIVE: The association between socioeconomic status (SES) and body mass index (BMI) in middle-income countries is mixed. Heterogeneity in SES indicators used could explain some differences. This study aimed to identify SES indicators consistently associated with BMI in Mexican adults in 2006, 2012, and 2016. METHODS: Data were obtained from the Mexican National Health and Nutrition Surveys of 2006, 2012, and 2016, including adults 20 to 59 years old. Given expected differences by sex, sex-stratified linear regression models were fitted for each survey. Age-adjusted and multivariate models were fit by using seven noncollinear SES indicators. RESULTS: In age-adjusted models, most SES indicators were associated with a higher BMI in men; mixed associations were found for women. In multivariate models, living in urban areas was associated with a higher BMI for both men and women in 2006 and 2012. Across all surveys, education was associated with a lower BMI in women, while household assets were associated with a higher BMI in men. CONCLUSIONS: The association between SES indicators and BMI is complex. Differences by sex need to be explicitly recognized when modeling this association. Approaches that rely on a single indicator could be confounded by other SES indicators. Adjusted models show the specific SES attributes that may influence BMI.