WIC Food Package Changes: Trends in Childhood Obesity Prevalence.

OBJECTIVES: To evaluate the association of the 2009 changes to the US Special Supplemental Nutrition Program for Women, Infants, and Children (WIC) food package and childhood obesity trends. We hypothesized that the food package change reduced obesity among children participating in WIC, a population that has been especially vulnerable to the childhood obesity epidemic. METHODS: We used an interrupted time-series design with repeated cross-sectional measurements of state-specific obesity prevalence among WIC-participating 2- to 4-year-old children from 2000 to 2014. We used multilevel linear regression models to estimate the trend in obesity prevalence for states before the WIC package revision and to test whether the trend in obesity prevalence changed after the 2009 WIC package revision, adjusting for changes in demographics. In a secondary analysis, we adjusted for changes in macrosomia and high prepregnancy BMI. RESULTS: Before the 2009 WIC food package change, the prevalence of obesity across states among 2- to 4-year-old WIC participants was increasing by 0.23 percentage points annually (95% confidence interval: 0.17 to 0.29; P < .001). After 2009, the trend was reversed (-0.34 percentage points per year; 95% confidence interval: -0.42 to -0.25; P < .001). Changes in sociodemographic and other obesity risk factors did not account for this change in the trend in obesity prevalence. CONCLUSIONS: The 2009 WIC food package change may have helped to reverse the rapid increase in obesity prevalence among WIC participants observed before the food package change.