Trends in Severe Obesity Among 23 Million U.S. Children Aged 2–4 Years Who Enrolled in WIC — United States, 2000–2014

To examine trends in prevalence of severe obesity by age, sex, and race/ethnicity (non-Hispanic [NH] white, NH black, Hispanic, American Indian/Alaska Native [AIAN], and Asian/Pacific Islander [PI]) among U.S. children aged 2–4 years who enrolled in WIC during 2000–2014.

A cross-sectional study used data of 22.6 million young children enrolled in WIC from 50 states, DC, and 5 U.S. territories. Children’s weights and heights were measured. Severe obesity was defined as sex-specific BMI-for-age≥120% of the 95th percentile. Children whose sex, weight, height, or BMI were missing or biologically implausible were excluded. Joinpoint regression was used to identify best fitting points where statistically significant changes in overall trend occurred. Log binomial regression adjusted for age, sex, and race/ethnicity was used to estimate prevalence ratios between two inflection years. Adjusted prevalence differences (APD) were calculated based on prevalence at beginning of period and prevalence ratios.

During 2000–2004, prevalence of severe obesity increased significantly overall (from 1.80% to 2.11%, APD=0.26%) and among all the age, sex, and racial/ethnic groups except for Asian/PI (APD ranged from 0.05% to 0.54% across groups with increases). The largest increases occurred in AIANs and 4-year-olds. During 2004–2010, prevalence decreased significantly overall (APD= -0.05%), among boys, 2- and 3-year olds, NH blacks, and Asians/PIs (APD ranged from -0.05% to -0.18%). During 2010–2014, prevalence decreased significantly overall (from 2.12% to 1.96%, APD= -0.14) and among all demographic groups (APD ranged from -0.04% to -0.30%). The largest average relative annual decreases occurred in AIANs and Asians/PIs.

This study provides updated prevalence and trends of severe obesity among young children enrolled in WIC and reports recent modest declines in severe obesity in all subgroups. Ongoing surveillance is needed to assess whether declines continue into the future among low-income children.