Pathways to obesity in a developing population: The Guangzhou Biobank Cohort Study.

BACKGROUND: 'Environmental mismatch' may contribute to obesity in rapidly developing societies, because poor early life conditions could increase the risk of obesity in a subsequently more socio-economically developed environment. In a recently developing population (from southern China) we examined the association of life-course socio-economic position (SEP) with obesity. METHODS: In a cross-sectional study of 9998 adults from the Guangzhou Biobank Cohort Study (phase 2) examined in 2005-06, we used multivariable linear regression to assess the association of SEP at three life stages (proxied by parental possessions, education and longest held occupation) with obesity [body mass index (BMI) and waist-hip ratio (WHR)] in men and women. RESULTS: There was no evidence that socio-economic position trajectory had supra-additive effects on BMI or WHR. Instead in women, higher SEP at any life stage usually contributed to lower BMI and WHR; e.g. women with higher early adult SEP had lower BMI [-0.45; 95% confidence interval (CI) -0.71 to -0.19) and WHR (-0.02; 95% CI -0.02 to -0.012]. In contrast, in men, higher childhood SEP was associated with higher BMI (0.53; 95% CI 0.18 to 0.88) and WHR (0.01; 95% CI 0.003 to 0.02) as was high late adulthood SEP with BMI (0.36; 95% CI 0.07 to 0.64). CONCLUSIONS: This study provides little support for environmental mismatch over the life course increasing obesity in this rapidly transitioning southern Chinese population. However, our findings highlight different effects of the epidemiologic transition in men and women, perhaps with pre-adult exposures as a critical window for sex-specific effects.