Genetic Contributions to BMI Fluctuation and Its Associations With BMI and Its Trajectories Over Adolescence and Early Adulthood: A 25-Year Follow-Up Longitudinal Study of Finnish Twins.

Abstract

We examined how BMI, BMI trajectories, and BMI fluctuation around these trajectories in adolescence were correlated with BMI trajectories and BMI fluctuation in early adulthood, as well as the genetic basis of these associations. BMI data from Finnish twins (N = 1379, 48% males) were collected at ages 11.5, 14, 17.5, 24, and 37 years. BMI trajectories in adolescence (11.5-17.5 years) and early adulthood (17.5-37 years) were estimated using linear mixed-effect models. BMI fluctuation was calculated as the average squared differences between observed and expected BMI around these trajectories. Genetic twin models and a polygenic risk score for BMI (PRS_BMI) were used to assess genetic contributions to BMI fluctuation and its associations with BMI and BMI trajectories. Adolescent BMI fluctuation was positively correlated with early adulthood BMI trajectories in females, while in males, adolescent BMI trajectories were positively associated with BMI fluctuation in early adulthood. Genetic factors affected BMI fluctuation in both adolescence and early adulthood when estimated using twin modelling and PRS_BMI. Adolescent BMI was positively associated with early adulthood fluctuation in both sexes, with genetic factors playing a role (genetic correlations .08-.29). It was concluded that genetic factors play a significant role in BMI fluctuations in adolescence and early adulthood, with some overlap with the genetics of BMI.