The effect of the 2009 WIC food package change on childhood obesity varies by gender and initial weight status in Los Angeles County

Objective: To assess whether the effect of the 2009 women, infants, and children (WIC) food package change on obesity outcomes varies by initial weight status and gender. Methods: Using 2003 to 2016 data from Los Angeles County, we compared growth trajectories and obesity at age 4 years among children exposed to WIC after the food package change (n = 53 075) vs children exposed before (n = 53 075). Analyses were stratified by gender and initial weight status: low weight-for-height z-score (WHZ <= 25th percentile), average WHZ (25th < WHZ < 75th percentile), and high WHZ (WHZ >= 75th percentile). Within strata, children exposed to the new vs old packages were matched on sociodemographic characteristics and compared using growth models and Poisson regression. Results: Mean WHZ trajectories for children exposed to the new food package, compared with the old, tended to be lower during ages 1 to 5 years. For boys, the new food package was associated with 10% to 14% lower obesity risk at age 4 years in all initial weight status strata. For girls, the new package was associated with 16% lower obesity risk at age 4 years only for those with average WHZ at baseline. Conclusions: The change in WIC food packages appears to be associated with obesity prevention benefits for boys regardless of initial weight status, with more limited benefits for girls.