Social Mobility of the Father and Relative Body Weight of Offspring: A Three-Generation Study

This study investigates the relation between intergenerational social mobility and body mass index (BMI) across three generations, focusing on age and sex differences.

The sample consisted of four child cohorts (born in 1980, 1983, 1985, 1988) measured annually from 6 to 11, 9 to 14, 11 to 16, and 14 to 18 years of age, examined between 1994 and 1999 in Poland. Body height and weight were recorded for 4196 grandfather-father-son/daughter triplets. BMI was calculated and standardized for age (Z-BMI). Social mobility was classified as upward, downward, "lower" stable, and "upper" stable. Kruskal-Wallis test was conducted to assess the relationship between social mobility and Z-BMI across different age groups and sexes.

In the parental generation, a significant effect of upward mobility was found in fathers. In the third generation, girls from "upper" group had significantly higher Z-BMI in comparison with "lower" and upwardly mobile peers, while boys from "upper" and upwardly mobile groups had significantly higher Z-BMI compared to the "lower" group. When analyzing specific age cohorts, significant effects were found in the two youngest cohorts, where children from the "upper" group had higher Z-BMI compared to their "lower" peers; moreover, the youngest children from upwardly mobile families had higher Z-BMI compared to the "lower" counterparts. Among adolescent girls born in 1983, the significant association between social mobility and BMI showed an emerging marginal trend in the opposite direction.

This study identified age- and sex-related variation in the associations between intergenerational social mobility and BMI, contributing to a broader understanding of how intergenerational processes relate to physical development.