Modeling BMI z score lability during childhood as a function of child temperament and genetic risk for obesity

Objective: This study aimed to examine whether child genetic risk for obesity and temperament (i.e., negative affectivity, effortful control) accounted for stability versus lability in children's weight status (BMI z score) over time. Methods: A total of 561 adopted children (42% female; 56% Caucasian, 13% African American, 11% Latino, and 20% other) and their birth and adoptive parents were followed from birth to age 9 years. The multilevel location-scale model was used to examine whether child genetic risk for obesity and temperament were related to differences in level and lability in child BMI z scores over time. Results: For the full sample, higher levels of child negative affectivity were associated with greater BMI z score lability, whereas higher levels of effortful control and children's mean-level BMI z scores were related to less lability across childhood. Additional analyses examined associations within groups of children with healthy versus overweight/obesity weight statuses. Within the healthy weight status group only, better effortful control was associated with more stable BMI z scores, whereas genetic risk for higher BMI was associated with more labile BMI z scores. Conclusions: These findings provide insights into factors that can be harnessed to redirect unhealthy trajectories as well as factors that may challenge redirection or maintain a healthy trajectory.