Daepp MIG, Gortmaker SL, Wang YC, Long MW, Kenney EL. WIC Food Package Changes: Trends in Childhood Obesity Prevalence. Pediatrics. 2019;143:e20182841. doi: 10.1542/peds.2018-2841.
The Special Supplemental Nutrition Program for Women, Infants, and Children (WIC) supports purchases of nutrient-dense foods and beverages for more than ½ of all US infants and ¼ of all low-income pregnant and postpartum women and children <5 years old, based on income eligibility criteria. In 2009, WIC voucher purchase specifications were changed to align with dietary guidelines, to promote consumption of fruits/vegetables and whole grains and reduce consumption of juice and cheese. In this study of 2- to 4-year-old children participating in WIC at different time points from 2000-2014, the authors found that obesity prevalence changed by -0.57 percentage points each year after the policy change (95% confidence interval [CI]: -0.69 to -0.44; p<.001).
Childhood obesity in the US has increased markedly since the early 1990s, affects low-income and racial/ethnic-minority children disproportionately, and is fueled by many factors including calorie-dense diets in the toddler and early childhood years. Data from other sources indicates that the 2009 WIC policy change led to increases in the intake of fruits and whole grains, and decreases in juice purchases, but prior to this study there had been no assessments of impact on childhood obesity prevalence. The authors used a quasi-experimental study design (i.e., to evaluate patterns of childhood obesity before and after a policy change), with repeated cross-sectional measurements (called an interrupted time series) of different cohorts of children who were enrolled in the WIC program. To account for social determinants of health known to be associated with childhood obesity, they adjusted for shifting proportions of children of different racial/ethnic backgrounds participating in WIC over time, and also for different exposures of WIC-participating children to poverty over the study period. In analyses adjusted for social determinants, the authors found that rates of obesity (sex-specific body mass index ≥95th percentile for age) were changing +0.23 percentage points each year from 2000-2008 (95% CI: +0.17 to +0.29; p<.001), in strong contrast to the negative annual change (i.e., improvement) reported above. This translated into a net change of -0.34 percentage points per year (0.23 - 0.57 = -0.34) as an effect of the WIC policy change.