Childhood obesity is associated with negative health consequences in childhood (1) that continue into adulthood (2), putting adults at risk for type 2 diabetes, cardiovascular disease, and certain cancers (1). Obesity disproportionately affects children from low-income families (3). Through a collaboration with the United States Department of Agriculture (USDA), CDC has begun to use data from the Special Supplemental Nutrition Program for Women, Infants, and Children (WIC) Participants and Program Characteristics (WIC PC) to replace the Pediatric Nutrition Surveillance System (PedNSS) (4,5) for obesity surveillance among young children from low-income families. CDC examined trends in obesity prevalence during 2000–2014 among WIC participants aged 2–4 years using WIC PC data. Overall obesity prevalence increased from 14.0% in 2000 to 15.5% in 2004 and 15.9% in 2010, and then decreased to 14.5% in 2014. During 2010–2014, the prevalence of obesity decreased significantly overall, among non-Hispanic whites, non-Hispanic blacks, Hispanics, American Indian/Alaska Natives and Asians/Pacific Islanders, and among 34 (61%) of the 56 WIC state agencies in states, the District of Columbia, and U.S. territories. Despite these declines, the obesity prevalence among children aged 2–4 years in WIC remains high compared with the national prevalence of 8.9% among children aged 2–5 years in 2011–2014. Continued initiatives to work with parents and other stakeholders to promote healthy pregnancies, breastfeeding, quality nutrition, and physical activity for young children in multiple settings are needed to ensure healthy child development.
To improve maternal and child health among women and children at risk for poor nutrition, WIC provides supplemental foods, nutrition education, and health care referral for low-income women who are pregnant, postpartum, or breastfeeding, and infants and children aged up to 5 years. WIC is administered in each state or territory by state health departments or Indian tribal organizations. WIC PC is a biennial census conducted by the USDA in even years that includes participants certified to receive WIC benefits in April of the reporting year. To be eligible for WIC, women, infants, and children have to meet residential, income (gross household income ≤185% of the U.S. Poverty Level or adjunctively eligible for other child nutrition programs), and nutrition risk requirements.* Children’s weight and height were measured by clinic-trained staff members according to a standard protocol†; children’s weight and height records during the most recent certification or recertification were included. Obesity was defined as sex-specific body mass index (BMI)-for-age ≥95th percentile on the 2000 CDC growth charts.
JoinPoint regression was used to identify the inflection years when changes in the overall trend occurred. Log binomial regression adjusted for age, sex, and race/ethnicity was used to estimate prevalence ratios that represent relative changes in prevalence between two inflection years. Differences in adjusted prevalence were then calculated ([prevalence at beginning of period] x [adjusted prevalence ratio] – [prevalence at beginning of period]). Changes in obesity prevalence were considered statistically significant if the 95% confidence intervals for differences in adjusted prevalence did not include zero.
Data from the WIC state agencies in 50 states, the District of Columbia, and five U.S. territories are included in the analyses. Approximately 90% of participants lived in households with gross incomes ≤185% of the U.S. Poverty Level. Approximately 75% of the anthropometric data were collected within 6 months before April of the reporting year. Data on 24,472 (0.11%) children from Hawaii in 2002 and 2004 were excluded because these prevalence estimates differed by >10 percentage points from the values predicted by a robust regression model, as were children whose weight and height were measured >1 year before the reporting year (n = 1,062 [0.005%]) or whose sex, weight, height, or BMI were missing or biologically implausible (194,526 [0.85%]) (6). The final analytic sample included 22,553,518 children aged 2–4 years from 56 WIC state agencies.
During 2000–2010, overall obesity prevalence increased significantly from 14.0% (2000) to 15.5% (2004) and 15.9% (2010); during 2010–2014, obesity prevalence decreased significantly to 14.5% (2014) (Figure) (Table). In a sensitivity analysis to assess the impact on the effect from Hawaii and the Northern Mariana Islands, which did not have consistent, reliable data during 2000–2014, the overall prevalence remained the same during 2000, 2004, and 2010 and increased slightly from 14.5% to 14.6% in 2014, when data from Hawaii and the Northern Mariana Islands were excluded. Patterns in overall obesity trends remained the same.
Obesity prevalence in all years was highest among American Indians/Alaska Natives and Hispanics. Among non-Hispanic whites, non-Hispanic blacks, Hispanics, and American Indians/Alaska Natives, prevalence increased significantly during 2000–2004, then decreased significantly during 2010–2014. Among Asians/Pacific Islanders, prevalence decreased significantly throughout the study period (Figure). Patterns in obesity trends remained the same for all racial/ethnic groups if Hawaii and the Northern Mariana Islands were excluded.
The JoinPoint analysis identified 2004 and 2010 as the inflection years for overall obesity trend. Obesity prevalences by WIC state agency are observed at four time points (2000, 2004, 2010, and 2014), with comparisons in adjusted prevalence during 2004 and 2000, 2010 and 2004, and 2014 and 2010 (Table). Among the 54 state agencies with data for 2000 and 2004, an increase in obesity prevalence was observed in 48 (89%); among these, 38 (70%) were statistically significant; the largest increase occurred in Kansas (from 11.8% to 16.7%). Obesity prevalence decreased for four (7%) WIC state agencies; Puerto Rico was the only WIC state agency with a significant decrease (from 22.1% to 21.3%) (Table).
Among the 54 WIC state agencies with data for 2004 and 2010, an increase in prevalence occurred in 26 (48%), including 17 (31%) that were statistically significant; a decrease occurred in 27 (50%) WIC state agencies, including 20 (37%) that were statistically significant. The largest increase in obesity prevalence occurred in New Mexico (from 11.0% to 15.7%) and the largest decrease occurred in Illinois (from 20.3% to 15.7%) (Table).
Among the 56 WIC state agencies with data for 2010 and 2014, only nine (16%) experienced an increase in obesity prevalence, including four (7%) in which the increase was statistically significant. The largest significant increase occurred in Nebraska (from 14.4% to 16.9%). In contrast, a decrease in obesity prevalence occurred in 45 (80%) WIC state agencies, including 34 (61%) in which the difference was statistically significant. The adjusted prevalence decreased by more than 3 percentage points in six WIC state agencies; the largest significant decrease was in Puerto Rico (from 20.3% to 13.9%).
The prevalence of obesity among young children from low-income families participating in WIC in U.S. states and territories was 14.5% in 2014. This estimate was higher than the national estimate (8.9%) among all U.S. children in a slightly different age group (2–5 years) based on data from the 2011–2014 National Health and Nutrition Examination Survey (7). Since 2010, statistically significant downward trends in obesity prevalence among WIC young children have been observed overall, in all five racial/ethnic groups, and in 34 of the 56 WIC state agencies, suggesting that prevention initiatives are making progress, potentially by impacting the estimated excess of calories eaten versus energy expended for this vulnerable group (8).
Nutrition during pregnancy and early childhood is critical for healthy child growth and development. A recent review of factors contributing to childhood obesity identified risk factors present during pregnancy and the first 2 years of life, including high maternal prepregnancy BMI, excess maternal gestational weight gain, gestational diabetes, high infant birth weight, and rapid infant weight gain that can influence the risk for obesity in later childhood (9). The USDA WIC program reaches low-income mothers and children with nutritional risk during this critical developmental period. WIC promotes healthy eating and provides nutrition education that emphasizes the nutritional needs of women who are pregnant, postpartum, or breastfeeding, and children aged up to 5 years. In 2009, the WIC food packages were revised§ to align with the Dietary Guidelines for Americans and the infant feeding practice guidelines of the American Academy of Pediatrics. The revisions promote and support breastfeeding, provide WIC participants with a wider variety of healthy food options, and improve availability of and access to healthy foods in communities (10).
Other factors also might be contributing to the modest declines in obesity among WIC young children. Local, state, and national obesity initiatives and reports such as Let’s Move,¶ the White House Childhood Obesity Task Force report,** and the Institute of Medicine recommendations†† have raised awareness and drawn the attention of stakeholders, including parents, early care and education (ECE) providers, community and business leaders, industry, health care providers, and public health officials. A number of federal initiatives have provided support to states and localities to assist ECE programs to improve nutrition, breastfeeding support, physical activity, and screen time standards. For example, CDC supports states in embedding these standards in their ECE systems through various mechanisms, including the State Public Health Actions§§ and the ECE Obesity Prevention cooperative agreements.
The findings in this report are subject to at least two limitations. First, findings might not be generalizable to all young children from low-income families, because the study includes only young children who participated in WIC and only about 50% of WIC eligible young children were enrolled in the program.¶¶ Second, findings of this study are not directly comparable to those based on the older PedNSS data, which also included WIC participants (4,5). Data collected by PedNSS in January–December calendar years included participants from some other child nutrition programs (<20%), in addition to WIC, but did not have consistent data for all WIC state agencies over time.
Despite the recent declining trends, the obesity prevalence for young, low-income children in WIC remains high at 14.5% in 2014. To reduce the high prevalence of early childhood obesity among low-income families, new and continued implementation of evidence-based measures are needed to support and educate pregnant women, ensure parents and families have the appropriate information about healthy behaviors, and encourage stakeholders across various settings and sectors to create supportive nutrition and physical activity environments.