Examining the relationship between obesity and math performance among Canadian school children: a prospective analysis.

OBJECTIVES: To determine whether obesity during the pre-school to primary school years was related to math performance, independently of other factors, in a large representative sample of Canadian children. Our main hypothesis was that obese children would obtain lower overall math scores than their non-obese peers.
METHODS: Participants of the National Longitudinal Survey of Children and Youth comprised the sample for our analysis (n = 4 664). Obesity was based on mother-reported height and weight and IOTF age- and sex-specific body mass index cut-offs, and was assessed when the cohort was aged 2-5 years and 8-11 years. Children were classified as 'never obese', 'grew out of obesity', 'developed obesity' or 'always obese', depending on their obesity status at these two time points. The outcome was performance on a standardized math test that was administered when the cohort was aged 8-11 years. Statistical analysis was conducted using multivariate linear regression methods.
RESULTS: Children who 'grew out of obesity' scored on average 11 points higher on the math test (p<0.0001) than children who were 'never obese.' Children who were 'always obese' and those that 'developed obesity' performed no differently on the math test than children who were 'never obese'. No interactions between sex and obesity status were found.
CONCLUSIONS: Childhood obesity in this study did not lead to poor math performance. Being obese in the pre-school years and normal weight in primary school, however, was associated with improved math performance. This finding points to a potential nutritional window for early child development.