October 16, 2008

Bad ‘Brain Circuitry’ May Explain Obesity

Using brain imaging and chocolate milkshakes, U.S. scientists say people with weakened brain "reward circuitry" are at increased risk of weight gain.

Researchers at the University of Oregon's Lewis Center for Neuroimaging say food intake is associated with dopamine release, while pleasure from eating correlates with the amount of dopamine release. Studies suggest the obese have fewer dopamine receptors in the brain and have to eat more than lean people to be satisfied.

One study involved 43 female college students ages 18 to 22 with a mean body mass index of 28.6. The second study looked at 33 adolescent girls, ages 14-18, with a mean BMI of 24.3. Most of the participants were tested for the presence of a genetic variation known as the Taq1A1 allele, which is linked to a lower number of dopamine D2 receptors. Researchers tracked changes in BMI over a year.

The study, published in the journal Science, found participants with decreased striatal activation in the brain in response to the chocolate milkshake, and those with the A1 allele, were more likely to gain weight over time.

"Certain biological factors may impact one's risk for weight gain, which is important in order to better understand how we can eventually intervene and prevent obesity," the researchers said in a statement.