Obesity's Chicken or Egg

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Science  01 Apr 2011:
Vol. 332, Issue 6025, pp. 15
DOI: 10.1126/science.332.6025.15-a
CREDIT: STICE ET AL., J. NEUROSCI. 31, 4360 (2011)

Altered reward circuitry in the brain may play a role in obesity. One change that has been observed is that overweight people have fewer dopamine D2 receptors in the brain striatum; however, it is unclear whether this is a cause or consequence of overeating. Stice et al. used functional magnetic resonance imaging to look at vulnerability to obesity by examining neural responses to food and related cues in high-risk though still-lean adolescents. They found that a corticostriatal network responded to food receipt, but not to anticipation of food-related cues, more strongly in these high-risk people. A related network in high-risk individuals also responded more to the receipt of money. These people also showed greater activation of the oral regions of the somatosensory cortex in response to palatable food intake, a result specific for food rather than money. Thus, youths at risk for obesity initially had a generally elevated reward region responsivity. When coupled with an increased responsivity of oral somatosensory regions, this may result in overeating that subsequently produces dopamine receptor down-regulation and elevated incentive salience of food cues.

J. Neurosci. 31, 4360 (2011).

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