1 UK Health Forum, London. United Kingdom; 2 Department of Epidemiology and Public Health, University College London (UCL), Londond, United Kingdom.
Aim: To test the nutrition transition proposition of a cross-over to higher obesity prevalence among the most disadvantaged women as Mexico develops economically. It is hypothesised that the reversal of the education gradient will be observed first among more wealthy groups followed by poorer groups. Methods: Data came from four nationally representative cross-sectional surveys (1988, 1999, 2006 and 2012). Response rate ranged from 80% to 97%. Sample sizes for non-pregnant women aged 20 to 49 ranged from 10,318 to 14,531. Weight and height were measured. Trends in educational inequalities in obesity over the period 1988-2012 were investigated in urban and rural areas. Educational inequalities were then stratified by an asset-based household wealth index. Effect modification by wealth in the association between education and obesity was formally tested. Results: There was an inverse association between education and obesity among urban Mexican women since 1988 (higher education-lower obesity prevalence). Among rural dwelling women there was no association throughout the study period 1988-2012. In both urban and rural areas the association between education and obesity varied by level of wealth in the earlier surveys (interaction p<0.001). For example, in urban areas in 1988, among the richest group, one level decline in education was associated with a 43% increase in the prevalence of obesity (PR 1.43 95% CI 1.25, 1.65); whereas among the poorest, education was not associated with obesity (PR 0.92 CI 0.71, 1.20). In the last two survey waves, there was an emerging inverse association between education and obesity among the poorest women. Education became protective of obesity across all wealth groups (interaction p>0.05). Conclusion: In Mexico there was evidence of a cross-over to higher rates of obesity among the most disadvantaged women upon reaching a threshold level of household wealth. This was consistent with the nutrition transition proposition.