The new child food package is associated with reduced obesity risk among formula fed infants participating in the Special Supplemental Nutrition Program for Women, Infants and Children (WIC) in Los Angeles County, California, 2003-2016

Background The Special Supplemental Nutrition Program for Women, Infants and Children (WIC) changed the food packages provided to its participants in 2009, to better align them with the Dietary Guidelines for Americans. Previous research found that the 2009 WIC food package change was associated with reduced obesity risk, particularly among breastfed infants but also among those who were never breastfed. The objective of this study was to determine if the new child food package introduced in 2009, including more produce and whole grains for 1-4-year old children, was associated with healthier growth trajectories and reduced obesity risk at age 4 years among children who were exclusively formula fed during infancy. Methods Administrative data on WIC-participating children in Los Angeles County, 2003-2016, were used (N = 74,871), including repeated measures of weight and length (or height); child's age, gender, and race/ethnicity; maternal education and language; and family poverty. Gender-stratified spline mixed models were used to examine weight-for-height z-score (WHZ) growth trajectories from 0 to 4 years and Poisson regression models were used to assess obesity (BMI-for-age > 95th percentile) at age 4. The main independent variable was duration of receipt (dose) of the new child package, categorized as 0, > 0 to < 1, 1 to < 2, 2 to < 3, 3 to < 4, and 4 years. Results WHZ growth trajectories were similar for children across new child package dose groups. Boys and girls who were fully formula fed during infancy but received the new child food package for 4 years had a 7% (RR = 0.93; 95%CI = 0.89-0.98) and a 6% (RR = 0.94; 95%CI = 0.89-0.99) lower obesity risk, respectively, compared to children who received the new child food package for 0 years. There were no differences in obesity risk for children receiving < 4 years of the new child package vs. 0 years. Conclusions Providing healthy foods during childhood to children who were exclusively formula fed as infants was associated with modest improvements in obesity outcomes. While breastfeeding promotion should still be prioritized among WIC participants, providing healthy foods during childhood may provide health benefits to formula fed children, who comprise a sizeable proportion of children served by WIC.