Background Despite comparatively lower socioeconomic status (SES), immigrants tend to have lower body weight and weaker SES gradients relative to US-born individuals. Yet, it is unknown how changes in SES over the life-course relate to body weight in immigrants versus US-born individuals.

Methods We used longitudinal data from a nationally representative, diverse sample of 13 701 adolescents followed into adulthood to investigate whether associations between SES mobility categories (educational attainment reported by individuals as adults and by their parents during adolescence) and body mass index (BMI) measured in adulthood varied by immigrant generation. Weighted multivariable linear regression models were adjusted for age, sex, race/ethnicity and immigrant generation.

Results Among first-generation immigrants, although parental education was not associated with adult BMI, an immigrant's own education attainment was inversely associated with BMI (β=−2.6 kg/m²; SE=0.9, p<0.01). In addition, upward educational mobility was associated with lower adult mean BMI than remaining low SES (β=−2.5 kg/m²; SE=1.2, p<0.05). In contrast, among US-born respondents, college education in adulthood did not attenuate the negative association between parental education and adult BMI. Although an SES gradient emerged in adulthood for immigrants, remaining low SES from adolescence to adulthood was not associated with loss of health advantage relative to US-born respondents of US-born parents of similar SES.

Conclusions Immigrants were able to translate higher SES in adulthood into a lower adult mean BMI regardless of childhood SES, whereas the consequences of lower childhood SES had a longer reach even among the upwardly mobile US born.