The Associations between Body Weight and Executive Function

Abstract

Executive functions are high level cognitive mechanisms that manage everyday thinking and behaviour. Miyake et al’s (2000) model separates executive function into three fundamental elements: shifting, inhibition and updating. Initially, a Systematic Review examined twenty-two papers. Most studies reported poorer executive function in obese individuals in clinical settings but there was a lack of work in community populations.

Study One examined the relationship between executive function and weight in 315 community–based individuals who completed a cognitive test battery testing shifting (Local-Global task), inhibition (Stroop task), updating (Keep-Track task), and a complex task (Random Number Generator). Body Mass Index (BMI) was calculated according to standard World Health Organisation (WHO) criteria. Self-reported depression, demographic and clinical variables were obtained. Quantile regressions, ANOVA and correlations revealed clear differences between the BMI categories across the cognitive tests with underperformance on tests of inhibition, shifting and updating in both obese class III and underweight categories.

Study Two examined the relationship between the performance-based cognitive tests employed in Study One and the self-report Behaviour Rating Inventory of Executive Function (BRIEF-A), to aid understanding of how deficits may impact individuals in their everyday life. A separate cohort of 400 community participants were recruited. Using quantile regression analysis, Study One results were not fully replicated in Study Two. Some limited differences were noted, with overweight and obese individuals underperforming in updating tasks in comparison to normal weight and underweight individuals. No associations between the BRIEF-A and cognitive tests were observed.

To conclude, there is some evidence to suggest that there is a link between weight and executive function but there were inconsistencies between the studies. The discussion highlights the need for further work to examine the reasons for these inconsistent effects.