Effects of Breastfeeding, Formula Feeding, and Complementary Feeding on Rapid Weight Gain in the First Year of Life.

Objective: To determine whether proportion of breast versus formula feeding and timing of complementary food introduction affect the odds of rapid gain in weight status in a diverse sample of infants.

Methods: Using data from Greenlight Intervention Study, we analyzed the effects of type of milk feeding (breastfeeding, formula, or mixed feeding) from the 2- to 6-month well visits, and the introduction of complementary foods before 4 months on rapid increase in weight-for-age z-score (WAZ) and weight-for-length z-score (WLZ) before 12 months using multivariable logistic regression models.

Results: Of the 865 infants enrolled, 469 had complete data on all variables of interest, and 41% and 33% of those infants had rapid increases in WAZ and WLZ, respectively. Odds of rapid increase in WAZ remained lowest for infants breastfeeding from 2 to 6 months (adjusted odds ratio [aOR] 0.34; 95% confidence interval [CI]: 0.17, 0.69) when compared to infants who were formula-fed. Adjusted for feeding, introduction of complementary foods after 4 months was associated with decreased odds of rapid increase in WLZ (aOR 0.64; 95% CI: 0.42, 0.96).

Conclusions: Feeding typified by predominant breastfeeding and delaying introduction of complementary foods after 4 months reduces the odds of rapid increases in WAZ and WLZ in the first year of life.