Association of Self-regulation With Obesity in Boys vs Girls in a US National Sample

IMPORTANCE Poor self-regulation in childhood is associated with increased risk of obesity. However, studies have assumed that greater self-regulation is associated with a lower obesity risk and have rarely examined differences in the association by sex. OBJECTIVES To examine how different levels of toddler self-regulation are associated with the prevalence of obesity at kindergarten age and whether the pattern of association is different between boys and girls. DESIGN, SETTING, AND PARTICIPANTS This was a prospective cohort study using data from the Early Childhood Longitudinal Study, Birth Cohort, a nationally representative sample of 10 700 US children born in 2001 and followed up through kindergarten entry (2006-2007). The analytic sample included 6400 children with observed toddler self-regulation. Data collection occurred in children's homes and consisted of a parent interview and direct assessment of the child. Data analysis took place between May 2016 and March 2018. EXPOSURES During a standardized, in-home, developmental assessment at 24 months of age, observers scored 4 dimensions of children's self-regulation: adaptability, attention, persistence, and frustration tolerance. Self-regulation scores ranging from a low of 4 to a high of 20 were grouped into quartiles. MAIN OUTCOMES AND MEASURES With use of measured heights and weights at 5.5 years, obesity was defined as a body mass index for age in the 95th percentile or greater. RESULTS The analytic sample consisted of 6400 children (3250 boys [50.6%, weighted]), with a median age of 24.1 months (interquartile range, 23.4-24.7 months) and 64.5 months (interquartile range, 61.7-67.6 months) at the self-regulation and body mass index assessments, respectively. Self-regulation scores were lower for boys than for girls (mean, 13.7 [95% CI, 13.4-13.9] vs 14.9 [95% CI, 14.7-15.1]), and the lowest self-regulation quartile comprised more boys than girls (weighted percentages, 66.5% vs 33.5%). The prevalence of obesity at 5.5 years was 19.2% among boys and 16.5% among girls. The pattern of association between toddler self-regulation and obesity at 5.5 years was different for boys and girls (P = .008 for interaction). Among boys, the adjusted prevalence of obesity was 19.7%, 18.3%, 20.3%, and 15.9% from lowest to highest quartile of self-regulation. In contrast, among girls, there was a U-shaped association (adjusted prevalence of obesity from lowest to highest self-regulation quartile, 17.0%, 10.3%, 10.7%, and 15.0%). CONCLUSIONS AND RELEVANCE In a large national cohort of US children, there were differences between boys and girls in the pattern of the association between self-regulation at 24 months and obesity at 5.5 years of age. Obesity prevention efforts aimed at improving self-regulation may have different results for girls and boys.