Amount, Preparation and Type of Formula Consumed and Its Association with Weight Gain in Infants Participating in the WIC Program in Hawaii and Puerto Rico

The aim of this study was to assess the association between amount (below or above recommendations), preparation (liquid vs. powder), and type (regular vs. hydrolysate) of infant formula consumed and weight in infants participating in the Women, Infant and Children (WIC) Program in Hawaii (HI) and Puerto Rico (PR). This was a secondary analysis of 162 caregivers with healthy term 0–2-month-old infants. Socio-demographics, infant food frequency questionnaires, and weight and length were assessed at baseline and after four months. Infant feeding practices were associated with weight-for-length z-scores using multivariable logistic regression. In total, 37.7% were exclusively breastfed and 27.2% were exclusively formula-fed. Among formula users, regular (63.6%) and powder (87.0%) formula were the most common; 43.2% consumed formula above recommendations. Most infants had rapid weight gain (61.1%). Infants fed regular formula had higher odds of overweight after four months (adjusted OR = 8.77, 95% CI: 1.81–42.6) and higher odds of rapid weight gain (adjusted OR = 3.10, 95% CI: 1.12, 8.61). Those exclusively formula fed had higher odds of slow weight gain (adjusted OR = 4.07, 95% CI: 1.17–14.2). Formula preparation and amount of formula were not associated with weight. These results could inform the WIC program’s nutrition education messages on infant feeding. Studies with longer follow-up are needed to confirm these results.