Measuring socio-economic change in a transitioning environment and its association with obesity using a case study from the urban South African Birth to Twenty cohort

Using data from the Birth to Twenty (Bt20) 1990 Johannesburg-Soweto born cohort, this paper aims to advance the understanding of links between the experiences of early life-course socio-demographic transitions and their association with body mass index (BMI) in a rapidly transitioning urban environment. A variety of regression modelling techniques are used to examine associations between early life-course socio-economic status (SES) transitions between birth and late adolescence and demographic change (move of address, or primary caregiver marital status change) with changes in BMI and/or obesity risk. Initial results show that for females, a strong positive association between residential mobility and BMI is observed for those also experiencing increased household SES between birth and 12/13 years, while no effect is observed for males. This was shown against a context of a tripling of the female overweight prevalence between late childhood and age 15 years. Further analyses will explore at what age between birth and late adolescence changes in the socio-demographic environment associate most with BMI change. Current findings suggest that targeting those on an upwardly mobile SES trajectory within changing urban environments undergoing nutrition transition with interventions to prevent obesity could have positive benefits.