The objective of this study was to investigate the impact of grandparental and parental education and parental educational trajectory on their adult offspring's overweight/obesity. We used register data from the Uppsala Birth Cohort Multigenerational Study, based on a representative cohort born in Sweden 1915–1929 (G1). Our sample included 5122 women and 11,204 men who were grandchildren of G1 (G3), their parents (G2), and grandparents. G3's overweight/obesity (BMI ≥25 kg/m2) was based on pre-pregnancy weight/height for women before their first birth (average age = 26 years), and measured weight/height at conscription for men (average age = 18 years). G1's, G2's, and G3's highest educational attainment was obtained from routine registers and classified as low, intermediate, or high based on respective sample distributions. Parental (G2) educational trajectory was defined as change in education between their own and their highest educated parent (G1), classified into 5 categories: always advantaged (AA), upward trajectory (UT), stable–intermediate (SI), downward trajectory (DT), and always disadvantaged (AD). We used hierarchical gender-stratified logistic regression models adjusted for G3's age, education, year of BMI collection, lineage and G2's year of birth and income. Grandparental and parental education were negatively associated with men's odds of overweight/obesity and parental education affected women's overweight/obesity risk. Furthermore, men and women whose parents belonged to the UT, SI, DT, and AD groups had greater odds of overweight/obesity compared to men and women whose parents belonged to the AA group (adjusted for G3's age, year of BMI collection, lineage, and G2's year of birth). These associations were attenuated when further adjusting for parental income and G3's own education. Socioeconomic inequalities can have long-term consequences and impact the health of future generations. For overweight/obesity in concurrent young cohorts, this inequality is not fully offset by upward educational trajectory in their parent's generation.
