Understanding family dynamics of obesity: Do parents and children lose and gain weight together?

Background: Obesity is prevalent among children and adults. Yet, understanding the relationship between parent and child weight trajectories is limited. Objective: (1) Examine the association between parent/child undesirable body mass index (BMI) category change. (2) Assess whether parental BMI category predicts child modified BMI z-score (mBMIz) annual change. Methods: We conducted a cross-sectional study of weight trajectories of 3821 parent-child dyads between March 2020 and December 2021 within the NYC Health + Hospitals system. Undesirability of child and parental BMI category change and the magnitude of mBMIz change by parental BMI are analysed. Results: Of 3821 children (mean [SD] baseline age, 9.84 [3.51]), 1889 were female. Of the 3220 parents (mean [SD] baseline age, 39.9 [8.51]), 2988 were female. Most children (53.52%) and parents (81.94%) presented with overweight and obesity. Undesirable BMI change in children was associated with concordant change in parents (adjusted OR: 1.7, 95% CI [1.45, 2.01], adjusted p < 0.001). Children of parents with obesity (adjusted coef: 0.076, 95% CI [0.004, 0.147], p < 0.038) and severe obesity (adjusted coef: 0.1317, 95% CI [0.024, 0.239], adjusted p < 0.016) demonstrated greater change in mBMIz than those of parents with normal weight or underweight. Conclusion: Parents and children have concordant weight trajectories, and public health interventions targeting both populations are essential.