Background: Whether self-control at school entry and changes in self-control in the early school years are predictive of BMI change and obesity onset over the next 8 years using longitudinal data on a nationally representative sample of US children.
Methods: Data from the Early Childhood Longitudinal Study-Kindergarten Class 1998 were analyzed. The analysis sample included 7060 children with data from kindergarten (mean age = 6 years) until eighth grade (mean age = 14 years). Self-control was assessed using teacher-reported scales. Child BMI and obese status (BMI ≥95th percentile for age and gender) were computed from height and weight measurements. Weighted linear and logistic regression models were estimated, adjusting for child's cognitive ability and a rich set of child and family covariates.
Results: High self-control in kindergarten was associated with lesser BMI increase (p < 0.05) and 43% lower odds (adjusted OR [AOR] = 0.57, 95% confidence interval [CI]: 0.38-0.86) of new onset obesity over the subsequent 8 years. The beneficial effect of high self-control in kindergarten emerged between fifth and eighth grade. Among children with low self-control in kindergarten, increase in self-control between kindergarten and fifth grade was associated with a 1.42 kg/m2 (95% CI: -2.82 to -0.02) lesser increase in BMI and 66% lower odds of new obesity onset (AOR = 0.34; 95% CI: 0.14-0.83), between kindergarten and eighth grade.
Conclusions: Low self-control at school entry is an important risk factor for unhealthy BMI increase during the transition to adolescence. Increase in self-control in the early school years may prevent unhealthy BMI increase and obesity in adolescence.
Keywords: BMI; BMI change; childhood obesity; obesity onset; self-control.