The Relationship Of Fitness And Body Mass With Intelligence In Preadolescent Children

PURPOSE: Obesity rates and physical inactivity have increased over recent decades. Prior research has found that greater levels of fitness are associated with aspects of intelligence quotient (IQ). IQ has been inversely correlated with body mass index (BMI). However, the influence of BMI and fitness (as measured by VO2max) on the different components of IQ (crystallized and fluid) in childhood has yet to be quantified. These analyses aimed to quantify the relationship of BMI and fitness with IQ in 8-10-year-old children. METHODS: Data were collected from 1,214 children (46.5% female; 9.47 ± 0.02 years) from the Greater Champaign-Urbana, IL and Boston, MA areas. Participant’s crystalized and fluid IQ scores were collected using standardized IQ tests (KBIT, KBIT-2, & Woodcock-Johson III Test). Participants also completed a VO2max test using a modified Balke protocol to assess aerobic fitness. The data were analyzed in SPSS using correlations and stepwise linear regressions. Three-step hierarchical regression analyses were conducted on IQ (Fluid, Crystallized, & Composite). Demographic variables of significance were included in Step 1. Step 2 included BMI and VO2max, and Step 3 included an interaction term of BMI x VO2max. RESULTS: Step 1 showed a significant effect for Crystallized, Fluid, and Composite IQ, ∆R2 ≥ 0.029, F(2, 1210) ≥ 13.050, p < .001; with an effect found for Mother’s Education; pr’s ≥ .159, t(1210) ≥ 5.590, p < .001, β's ≥ .160. Step 2 was also significant, ∆R2 ≥ 0.043, F(2, 1208) ≥ 11.847, p < .001. There was a significant effect of BMI in Step 2 for Fluid and Composite IQ, pr’s ≥ -.078, t(1208), ≥ -2.717, p ≤ .023, β's ≥ -.097. There was also a significant effect of VO2max in the second step for Crystallized and Composite IQ, pr’s ≥ .064, t(1208), ≥ 2.235, p ≤ .026, β's ≥ .079. Step 3 was not significant in any analysis. CONCLUSIONS: These data suggest that BMI and fitness are differential significant predictors of IQ in children. The results add to prior literature of the benefits of physiological health on brain health by providing insight into the relationship of body mass and fitness with IQ. The findings further support current public health incentives to decrease childhood obesity and increase physical activity to improve various aspects of health.