Obese children show hyperactivation to food pictures in brain networks linked to motivation, reward and cognitive control

Abstract

Objective: To investigate the neural mechanisms of food motivation in children and adolescents, and examine brain activation differences between healthy weight (HW) and obese participants.

Subjects: Ten HW children (ages 11-16; BMI < 85%ile) and 10 obese children (ages 10-17; BMI >95%ile) matched for age, gender and years of education.

Measurements: Functional magnetic resonance imaging (fMRI) scans were conducted twice: when participants were hungry (pre-meal) and immediately after a standardized meal (post-meal). During the fMRI scans, the participants passively viewed blocked images of food, non-food (animals) and blurred baseline control.

Results: Both groups of children showed brain activation to food images in the limbic and paralimbic regions (PFC/OFC). The obese group showed significantly greater activation to food pictures in the PFC (pre-meal) and OFC (post-meal) than the HW group. In addition, the obese group showed less post-meal reduction of activation (vs pre-meal) in the PFC, limbic and the reward-processing regions, including the nucleus accumbens.

Conclusion: Limbic and paralimbic activation in high food motivation states was noted in both groups of participants. However, obese children were hyper-responsive to food stimuli as compared with HW children. In addition, unlike HW children, brain activations in response to food stimuli in obese children failed to diminish significantly after eating. This study provides initial evidence that obesity, even among children, is associated with abnormalities in neural networks involved in food motivation, and that the origins of neural circuitry dysfunction associated with obesity may begin early in life.

Figure 1

(a) fMRI results from the between-group food vs non-food contrasts, co-registered with average structural MRI data from the participants. The maps are presented in the coronal perspective. The significance thresholds for display are set at P<0.001, uncorrected. The arrow highlights greater activation in the left OFC in the obese group than the HW group in the post-meal condition (x = −30, y = 35, z = −8; t = 3.92). (b) fMRI results from the direct group comparison (obese, HW) of the condition (pre-meal, post-meal) and stimulus type (food, control) co-registered with average structural MRI data from the participants. The maps are presented in the coronal perspective. The significance thresholds for display are set at P<0.001, uncorrected. The arrow highlights greater reduction of activation in the medial PFC for HW vs obese groups (x = 12, y = 47, z = 16; t = 4.64). fMRI, functional MRI; HW, healthy wright; OFC, orbitofrontal cortex; PFC, prefrontal cortex.