Importance: In the United States, pediatric and adult obesity remains unacceptably high, and varies geographically among adults. However, little is known about regional variation in child body mass index (BMI) in the US.
Objective: To describe variation in child BMI by United States Census region, and the association of individual-level characteristics (sex, race/ethnicity, birth weight, maternal education) with child BMI within each region.
Design: Pooled data from 25 prospective cohort studies in the Environmental influences on Child Health Outcomes (ECHO) Program that enrolled children born between 2000 and 2018.
Setting: Children residing in all four United States Census Bureau regions.
Participants: Samples of children followed from birth to 15 years.
Exposure: Region of residence(Northeast, Midwest, South and West) based on children’s residential zip codes at cohort enrollment.
Main Outcome and Measures: BMI was calculated as weight (kg)/height or length (m2). To account for differences in child age and sex, age-and sex-specific BMI z-scores were used as the main outcome measure.
Results: The final sample included 14,313 children with 85,428 BMI measurements; 49% female and 51%non-Hispanic white. Compared to the Northeast, average BMI z-score was significantly higher in the Midwest (β=0.09, 95% CI 0.05, 0.14) and lower in the South (β=-0.12, 95% CI -0.16, -0.08) and West (β=-0.14, 95% CI -0.19, -0.09) after adjustment for age, sex, race/ethnicity, and birth weight. Males had a lower average BMI z-score compared to females in the Midwest (β=-0.12, 95% CI -0.19, -0.05) and West (β=-0.12, 95% CI -0.20, -0.04).Compared to non-Hispanic white children, BMI z-score was generally higher among Hispanic and Black children but not across all regions. In all regions, BMI z-score was lower among children with college-educated mothers compared to children whose mothers did not graduate high school.
Conclusions and Relevance: Region of residence was associated with child BMI z-scores, even after adjustment for sociodemographic characteristics. The associations between BMI z-scores and sex or race/ethnicity varied by geographic region. Understanding regional influences can inform targeted efforts to mitigate BMI-related health disparities among children.