Helena H. Laroche, Robert B. Wallace, Linda Snetselaar, Stephen L. Hillis, Xueya Cai, Lyn M. Steffen

Parenthood is associated with decreased physical activity and dietary changes. Previously, mothers have been the focus of studies examining the influence of children on parents' body mass index (BMI), largely ignoring whether parenting affects fathers. This study assessed weight gain in mothers and fathers (by birth or other), using longitudinal repeated-measures models to assess BMI changes over time; parents were compared with nonparents. Data were from the Coronary Artery Risk Development in Young Adults cohort study and included 2,881 black and white adults, ages 18 to 30 years, without children at baseline (1985-1986), and from four urban locations. At each time point (years 2, 5, and 7), changes in BMI from baseline were analyzed, comparing those who had their children in their household at that time point (parents) and those without children (nonparents). The "child effect" is the mean difference in BMI change in parents compared with nonparents. In fathers, overall, the child effect was not significant (black males: 0.30; P=0.09; white males: 0.03; P=0.77). Among black men, however, interactions between age and parental status were significant (P=0.02). Black men who were aged 18 to 24 years at baseline and became fathers during the next 7 years demonstrated a significant child effect, gaining an average of 0.68 more in BMI than nonfathers (P=0.003). Mothers of both races demonstrated the child effect; for blacks it was 0.65 (P=0.003) and for whites it was 1.12 (P≤0.001). These data reveal that becoming a parent can affect the BMI of some adults and suggest that obesity-prevention interventions for children and adult-focused healthy-lifestyle interventions could have additional impact through a family focus targeting both parent and child outcomes.