Changes in Obesity Among US Children Aged 2 Through 4 Years Enrolled in WIC During 2010-2016

Prevalence of childhood obesity is high in the United States, especially among children from lower-income families.¹ Among children aged 2 through 4 years enrolled in the Special Supplemental Nutrition Program for Women, Infants, and Children (WIC), obesity prevalence increased between 2000 and 2010 but declined through 2014.² The decline was statistically significant among all racial/ethnic groups and in 34 of 56 state WIC agencies. The present study examines trends in overweight and obesity by age, sex, and race/ethnicity using WIC data from 2010 to 2016.

The WIC Participant and Program Characteristics survey includes all participants certified to receive WIC benefits. Data are extracted from state WIC agencies in April of even reporting years. WIC applicants must have nutritional risk and gross household income less than or equal to 185% of the US poverty level or participate in the Supplemental Nutrition Assistance Program, Medicaid, or Temporary Assistance for Needy Families. Children’s weight and height were measured by trained WIC professionals during certification or recertification visits. Children aged 2 through 4 years from 50 states, the District of Columbia, and 5 US territories enrolled in WIC in 2010, 2012, 2014, and 2016 were included in this study. The Centers for Disease Control and Prevention (CDC) determined that this study was not subject to review because deidentified secondary data were used.

Obesity was defined as a body mass index (BMI) at or above the 95th percentile for age and sex on the CDC growth charts.³ Overweight was defined as a BMI between the 85th and 95th percentiles. We examined trends for overweight and obesity combined and obesity alone by including data from all years in log-binomial models (SAS version 9.4, SAS Institute) adjusted for age, sex, and race/ethnicity. Trends were considered statistically significant with a 2-sided P < .01. To show relative and absolute prevalence differences between 2010 and 2016, we obtained adjusted prevalence ratios (APRs) from log-binomial regression and calculated adjusted prevalence differences (APDs) ([prevalence in 2010 × APR between 2010 and 2016] − prevalence in 2010). Interactions of survey cycle with age, sex, and race/ethnicity were tested to determine whether trends differed within demographic subgroups.

There were 12 403 629 children aged 2 through 4 years enrolled in WIC included (range, 3 307 442 in 2010 to 2 818 594 in 2016), excluding 171 272 children (1.4%) with missing age, sex, weight, height, or BMI information and 44 578 (0.4%) with biologically implausible anthropometric data. Compared with 2010, the 2016 study population had slightly lower proportions of non-Hispanic white and Hispanic children and higher proportions of non-Hispanic black and Asian/Pacific Islander children (Table 1).

The overall crude prevalence of obesity decreased from 15.9% in 2010 to 13.9% in 2016 (APD, −1.9% [95% CI, −1.9% to −1.8%]; APR, 0.88 [95% CI, 0.88-0.89]; P < .001) and the overall crude prevalence of overweight or obesity decreased from 32.5% in 2010 to 29.1% in 2016 (APD, −3.2% [95% CI, −3.3% to −3.2%]; APR, 0.90 [95% CI, 0.90-0.90]; P < .001). For overweight and obesity combined and obesity alone, multivariable trend analyses indicated statistically significant decreases in prevalence overall and in all age, sex, and racial/ethnic subgroups. Tests of interaction were significant (P < .001) for sex and racial/ethnic subgroups, with the greatest relative decreases among boys and Asian/Pacific Islander children (Table 2).

Obesity in low-income children aged 2 through 4 years declined between 2010 and 2016, although 13.9% had obesity in 2016. Results from the National Health and Nutrition Examination surveys indicated a quadratic obesity trend among children aged 2 to 5 years, decreasing from the 2007-2008 to 2011-2012 surveys and then increasing to the 2015-2016 survey.⁴ Differences may be due to a smaller sample of children from families of all income levels being used.

A study limitation is that fewer children were enrolled in WIC in recent years and characteristics of eligible children who were not enrolled might be different from those enrolled. However, demographic characteristics were accounted for in trend analyses.

Reasons for the declines in obesity among young children in WIC remain undetermined but may include WIC food package revisions⁵ and local, state, and national initiatives.⁶

Accepted for Publication: April 3, 2019.

Corresponding Author: Liping Pan, MD, MPH, Division of Nutrition, Physical Activity, and Obesity, Centers for Disease Control and Prevention, 4770 Buford Hwy, Mail Stop F-77, Atlanta, GA 30341 (Lpan@cdc.gov).

Author Contributions: Dr Pan had full access to all of the data in the study and takes responsibility for the integrity of the data and the accuracy of the data analysis.

Concept and design: Pan, Blanck.

Acquisition, analysis, or interpretation of data: All authors.

Drafting of the manuscript: Pan, Blanck.

Critical revision of the manuscript for important intellectual content: All authors.

Statistical analysis: Pan, Freedman, Blanck.

Administrative, technical, or material support: Pan, Potter, Blanck.

Supervision: Park, Blanck.

Conflict of Interest Disclosures: None reported.

Disclaimer: The findings and conclusions in this article are those of the authors and do not necessarily represent the official positions of the Centers for Disease Control and Prevention or the US Department of Agriculture.

Additional Contributions: Kelley S. Scanlon, PhD (US Department of Agriculture), reviewed the manuscript and provided critical comments. She did not receive compensation.