Additive influences of maternal and paternal body mass index on weight status trajectories from childhood to mid-adulthood in the 1970 British Cohort Study

This study aimed to (i) describe the weight status trajectories from childhood to mid-adulthood and (ii) investigate the influence of maternal and paternal body mass index (BMI) on offspring's trajectories in a nationally representative study in Great Britain. The sample comprised 4,174 (43% male) participants from the 1970 British Cohort Study with complete BMI data at ages 10, 26, 30, 34, and 42 years. Individuals' weight status was categorised as overweight/obese or non-overweight/obese at each age, and trajectories of weight status from 10 to 42 years of age were assessed. Sex-stratified multinomial logistic regression models were used to assess associations of maternal and paternal BMI with trajectory group membership, adjusting for potential confounders (e.g. socioeconomic position and puberty). Thirty per cent of individuals were never overweight/obese (reference trajectory), 6%, 44% and 8% had childhood, early- and mid-adulthood onset of overweight/obesity (respectively), and 12% other trajectories. In fully adjusted models, higher maternal and paternal BMI significantly increased the risk of childhood (relative risk ratio: 1.2-1.3) and early adulthood onset (1.2) of overweight/obesity in both sexes. Relative risk ratios were generally higher for maternal than paternal BMI in females but similar in males. Early puberty also increased the risk of childhood (1.8-9.2) and early-adulthood onset (3.7-4.7) of overweight/obesity. Results highlight the importance of primary prevention, as most individuals remained overweight/obese after onset. Maternal and paternal BMI had additive effects on offspring weight status trajectories across 32 years of the life course, suggesting that prevention/intervention programmes should focus on the whole family.