Severe obesity in children 17 to 24 months of age: a cross-sectional study of TARGet Kids! and Better Outcomes Registry & Network (BORN) Ontario

Objectives International data suggest the prevalence of severe obesity in young children may be increasing, yet no Canadian data are available. The objectives of this study were to examine definitions of severe obesity and to evaluate associated risk factors among young children in Ontario. Methods A cross-sectional study was conducted in children 17 to 24 months of age using two Ontario data sources: TARGet Kids! (n = 3713) and BORN Ontario (n = 768). Body mass index z score (zBMI) definitions were adapted from the World Health Organization (WHO) (z score > 3) and the US Centers for Disease Control (CDC) (> 120% of the 95th percentile) and applied to define severe obesity in young children. Multinomial logistic regression was used to evaluate associations between demographic and pregnancy risk factors and zBMI categories. Results A total of 1.1% (95% CI, 0.8-1.4) of children met the adapted WHO definition of severe obesity compared to 0.3% (95% CI, 0.2-0.6) using the CDC definition. Median neighbourhood household income (OR = 0.80, 95% CI, 0.69-0.93) and maternal pre-pregnancy BMI (OR = 1.08, 95% CI, 1.01-1.15) were associated with severe obesity in unadjusted analyses. After adjustment for potential confounders, the OR for the association between maternal pre-pregnancy BMI and severe obesity was 1.04 (95% CI, 0.94-1.15). Conclusion More than 1% of Ontario children met the adapted WHO definition of severe obesity in very early childhood. Modifiable risk factors were identified. Future studies are needed to understand the terminology, prevalence, and risk factors for severe obesity in young children across Canada.