Abstract
BACKGROUND: Early rapid weight gain (RWG) increases, whereas longer durations of breastfeeding decreases, odds for later obesity. OBJECTIVES: To determine the independent and interactive effects of early weight gain and diet on infant weight status trajectories and odds for overweight at 1 year. METHODS: We conducted secondary analysis on data from two longitudinal trials with repeated anthropometric measures. One trial consisted of predominantly or exclusively breastfed (BF, n = 97) infants, whereas the other consisted of exclusively formula-fed (FF, n = 113) infants. Weight-for-length z-score (WLZ) change from 0.5 to 4.5 months was used to categorize early weight gain as slow (<-0.67; SWG), normal (-0.67 to 0.67; NWG) or rapid (>0.67; RWG). Linear-mixed effects models were fit to examine the independent effects and interaction of early diet (BF, FF) and weight gain (SWG, NWG, RWG) groups on WLZ trajectories; logistic regression was used to assess odds for overweight at 1 year. RESULTS: While similar percentages (41%) of BF and FF infants experienced RWG, we found a significant diet × early weight gain group interaction (P < .001) on weight status. At 1 year, the WLZ of FF infants with RWG (1.57 ± 0.99) was twice that of BF infants with RWG (0.83 ± 0.92). Using BF infants with NWG as the reference group, FF infants with RWG had increased odds [OR: 25.3 (95% CI: 3.21, 199.7)] for overweight at 1 year, whereas BF infants with RWG did not. CONCLUSIONS: Early diet interacts with early weight gain and influences weight status trajectories and overweight risk at 1 year.