IQ and obesity in adolescence: a population-based, cross-sectional study

Background Previous studies have shown an association between low intelligence quotient (IQ), high body mass index and low socioeconomic status (SES). Objectives This study examined the cross-sectional association between IQ and obesity, exploring the roles of gender, SES and physical activity in this association. Methods Subjects were 235663 male and 169259 female adolescents assessed by the Israeli military draft board. Results Low IQ was significantly associated with increased odds of obesity among male (odds ratio [OR]=1.44, 95% confidence interval [CI]=1.36-1.52) and female adolescents (OR=1.61, 95% CI=1.51-1.73); this association was significantly stronger among female adolescents. Sobel tests indicated that physical activity had a significant mediating effect on this association for male and female adolescents, although more strongly for male adolescents. Dividing the sample according to SES, the association between low IQ and obesity was strongest in the high SES group (male adolescents: OR=1.26, 95% CI=1.10-1.43, female adolescents: OR=1.61, 95% CI=1.38-1.89), even when controlling for physical activity. Conclusions The findings suggest that low IQ is associated with increased odds of obesity, particularly in female adolescents and in adolescents with high SES. Physical activity has a mediating effect on this association, although more strongly for male than for female adolescents. Public health measures on decreasing obesity might focus on these groups.