The Effect of Child Weight on Academic Performance: Evidence using Genetic Markers

This paper examines the relationship between children’s weight and academic outcomes using genetic markers as instruments to account for the possible endogeneity of body size. We use medically assessed measures of body size which are more appropriate than the generally used BMI measures. OLS results indicate that leaner children perform better in school tests compared to their heavier counterparts, but the IV results, using genetic markers as instruments, show no evidence that fat mass affects academic outcomes. We compare these IV results to those using the instruments generally adopted in this literature. We show that the results are sensitive to the instrument set and argue that several of the commonly used instruments do not meet the exclusion restrictions required of a valid instrument.