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Brain Scans Shed Light on Why People Overeat

Targeting left posterior amygdala could lead to new treatments, study shows

MONDAY, Jan. 14, 2008 (HealthDay News) -- A brain area linked to the desire to overeat has been identified by U.S researchers, and treatments that target this region may help control chronic overeating.

For this study, researchers at the U.S. government's Brookhaven National Laboratory used functional MRI (fMRI) to observe how the brain responds to satiety messages delivered when the stomach is in various stages of fullness.

"By stimulating feelings of fullness with an expandable balloon, we saw the activation of different areas of the brain in normal weight and overweight people," study author Gene-Jack Wang, of Brookhaven's Center for Translational Neuroimaging, said in a prepared statement.

The researchers found that overweight people had less activation than normal weight people in a brain area called the left posterior amygdala when they were full. Overweight people were also less likely to report satiety when their stomach was moderately full.

"These findings provide new evidence for why some people will continue to eat despite having eaten a moderate-size meal," Wang said.

"This study provides the first evidence of the connection of the left amygdala and feelings of hunger during stomach fullness, demonstrating that activation of this brain region suppresses hunger," Wang said. "Our findings indicate a potential direction for treatment strategies -- be they behavioral, medical or surgical -- targeting this brain region."

Wang and colleagues also made an interesting finding about a hormone called ghrelin, which is known to stimulate the appetite and cause short-term satiety. People with higher increases in levels of ghrelin after their stomachs were moderately full had greater activation of the left amygdala.

"This indicates that gherlin may control the reaction of the amygdala to satiety signals sent by the stomach," Wang said.

The study was to be published in the Feb. 15 issue of NeuroImage.

More information

The U.S. National Institute of Diabetes and Digestive and Kidney Diseases has information about food portions.

SOURCE: Brookhaven National Laboratory, news release, Jan. 9, 2008
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