Body mass correlates inversely with inhibitory control in response to food among adolescent girls: an fMRI study

Abstract

Self-report and behavioral data suggest that impulsivity may contribute to the development and maintenance of obesity. Neuroimaging studies implicate a widespread neural network in inhibitory control and suggest that impulsive individuals show hypoactivity in these regions during tasks requiring response inhibition. Yet, research has not directly tested whether body mass correlates inversely with activation of these regions during response inhibition tasks. The present study used functional magnetic resonance imaging (fMRI) to investigate neural activations during a food-specific go/no-go task in adolescent girls ranging from lean to obese. When required to inhibit prepotent responses to appetizing food, body mass index (BMI) correlated with response inhibition at both the behavioral and neural levels, with more overweight adolescents showing greater behavioral evidence of impulsivity as well as reduced activation of frontal inhibitory regions, including superior frontal gyrus, middle frontal gyrus, ventrolateral prefrontal cortex, medial prefrontal cortex, and orbitofrontal cortex, than leaner individuals. As well, activation in food reward regions (e.g., temporal operculum/insula) in response to food images correlated positively with BMI. Results suggest that hypofunctioning of inhibitory control regions and increased response of food reward regions are related to elevated weight.

Figure 1

Scatterplot showing reaction times to go trials plotted as a function of BMI (N = 35). Subjects with higher BMIs showed significantly faster reaction times.

Figure 2

Scatterplot showing rate of commission errors (%), calculated as the number of commission errors divided by the total number of no-go trials, plotted as a function of BMI (N = 35). Subjects with higher BMIs showed a significantly higher rate of commission errors.

Figure 3

Coronal section showing less activation in the bilateral superior frontal gyrus (−21, 12, 57, Z = 3.96, pFDR = 0.003) extending into middle frontal gyrus in response to picture of dessert versus baseline fixation as a function of BMI. Although the correlation appears to be driven by 2 outliers, the effect remains significant at the p = 0.05 level when outliers are excluded.

Figure 4

Coronal section showing less activation in the right VLPFC (36, 42, 0, Z = 3.93, pFDR = 0.008) in response to picture of dessert versus baseline fixation as a function of BMI. Again, exclusion of the 2 apparent outliers still results in a significant effect at the p = 0.05 level.

Figure 5

Axial section of less activation in a region of the OFC (45, 33, −6, Z = 4.30, pFDR = 0.002) in response to picture of dessert versus baseline fixation as a function of BMI. Again, the effect remains significant at the p = 0.05 level when the two apparent outliers are excluded.

Figure 6

Activation in a region of the temporal operculum (−48, 9, −9, Z = 4.46, pFDR =0.01) in response to dessert versus baseline fixation was related to risk for future weight gain.