The Development of Body Mass Index from Adolescence to Adulthood: A Genotype-Family Socioeconomic Status Interaction Study

Body weight in adolescence and adulthood may result from the interplay between individuals’genetic characteristics and the social context in which they grow up, such as familysocioeconomic status (SES). However, evidence on the interaction between genetic propensityfor high body mass index (BMI) and family SES remains inconclusive. This study investigateswhether genetic associations with BMI differ among individuals from high-SES versus low-SESfamilies and whether these associations vary across the life course. Drawing on thecompensatory advantage model in sociology and the diathesis-stress model in psychology, Itest the hypothesis that genetic associations with BMI are stronger among individuals fromsocioeconomically disadvantaged families. Using data from the National Longitudinal Studyof Adolescent to Adult Health (Add Health), I assess the association between a polygenic indexfor BMI (BMI PGI) and BMI at four life stages: adolescence (≃ 16), early adulthood (≃ 22),adulthood (≃ 28), and later adulthood (≃ 37). Consistent with theoretical expectations, resultsshow that the BMI PGI is more predictive of BMI among individuals from low-SES familiesthan from high-SES families. The interaction weakens over the life course but persists amongindividuals with high BMI levels. These findings suggest that high-SES families may buffergenetic propensities for overweight and obesity, whereas low-SES environments mayexacerbate them, increasing the risk of elevated BMI. The results underscore the importanceof family socioeconomic background in shaping BMI outcomes and highlight howenvironmental interventions, such as promoting healthy eating and physical activity, may helpreduce social inequalities in health.