Trends in adults body mass index related to changes in socioeconomic status of 201 large Latin American cities

BACKGROUND: The prevalence of obesity has increased worldwide. The association between socioeconomic urban development in the nutritional status of the population in large cities from low and middle-income countries is unclear. AIM: Analyze how time trends in adult BMI vary across large cities and examine whether city socioeconomic status (SES) is related to adult BMI trends and whether individual level SES modifies this relationship. METHODS: We analyzed different cross-sectional health surveys done between 2000 and 2019, in Argentina, Brazil, Chile, Colombia, and Mexico, compiled as part of the SALURBAL study. Hybrid models adjusted for individual age and education were used to estimate associations of city-level education with differences in BMI, and associations of changes in city-level SES with changes in city BMI (change vs. change). Effect modification by individual-level education was assessed. Models were stratified by sex and country. RESULTS: We included 285,670 individuals from 201 cities. BMI increased over time in all countries except Brazil (women) and Chile (men), where it was not statistically significant. We did not find consistent evidence that average city education consistently modified trends in BMI. However, within city increases in city education were related to decreases in BMI in women (Chile and Colombia) and in men (Brazil, Chile, and Colombia). These effects were stronger in women with lower education. CONCLUSION: In low- and middle-income countries changes over time in city SES impact BMI trends in complex ways. A better understanding of the mechanisms involved may help develop better strategies to prevent increases in obesity.