Abstract
Background
Impulsivity is a risk factor for obesity. It has different underlying facets that can be assessed using questionnaires. Impulsivity can be further refined by the use of food-specific questionnaires, which measure a tendency to uncontrolled eating. We examined how these impulsivity measures relate to each other, to obesity, and to brain anatomy.
Methods
We assessed students in their first year of university - a risky period for weight gain- at the beginning (N = 2214) and at the end of the school year (N = 1145) using questionnaire measures of impulsivity, personality, stress reactivity and eating-specific traits. A subset of participants (N = 72) underwent T1-weighted MRI to investigate the brain correlates of impulsivity.
Results
Using factor analysis, we show that impulsivity can be stratified into three domains, which we label stress reactivity, reward sensitivity and self-control, while eating questionnaires resolve into a single latent factor - uncontrolled eating. A watershed model shows that uncontrolled eating mediates the effect of impulsivity traits on BMI. Self-control and stress reactivity scores are associated with a thinner lateral orbitofrontal cortex. In addition, stress reactivity correlates positively with amygdala and negatively with hippocampal volume. Longitudinally, lack of self-control, not uncontrolled eating, correlates with weight gain, while stress reactivity correlates with weight loss in male students.
Conclusions
The brain-impulsivity-obesity relationship is hierarchical. Structural brain differences relate to differences in impulsivity domains which affect BMI via uncontrolled eating. However, longitudinally, low self-control, not uncontrolled eating, is a predictor of weight gain in this sample.