Stomach Full? Brain May Not Know

Overweight people's brains may not know when their
stomachs are full, a brain scan study suggests.

The findings come from Gene-Jack Wang, MD, of Brookhaven National
Laboratory, Nora D. Volkow, MD, director of the National Institute on Drug
Abuse, and colleagues. These researchers have used real-time brain scans to
explore addictive behaviors. They're also looking at interactions between eating behaviors and
brain function.

In their new study, Wang and colleagues had 18 adult volunteers swallow
balloons -- sections of latex condoms tied off with unwaxed dental floss --
attached to a long tube. Once the balloons were in the patients' stomachs, the
researchers filled them with body-temperature water. The idea was to simulate
eating enough food to fill the stomach.

While the balloons were being filled, the researchers scanned the
patients' brains. At various times during the experiment -- when the
balloons were partially or fully filled -- the patients were asked how full
they felt, how uncomfortable they were, how hungry they were, and how much they
wanted food. The patients had not eaten since 7 p.m. the night before the
experiments, which were conducted between 11 a.m. and 1 p.m.

Perhaps not surprisingly -- as they had a tube going down their throat --
the patients reported only a little less hunger and a little more desire for food when the
balloons were full.

Interestingly, the thinner the subject, the more likely that person was to
report feeling full when the balloon was full. The heavier the patients, the
less likely they were to feel full with a filled water balloon in their
stomachs.

Filling the balloon triggered a response in the amygdala, the part of the brain that controls
emotional responses -- and possibly feeding behavior. Removal of a
specific part of the amygdala causes animals to eat uncontrollably.

Interestingly, the left rear amygdala became active when patients reported
feeling full.

"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 says in a news
release.

Wang went on to suggest that possible treatment options for obesity might
include brain surgery.

"Our findings indicate a potential direction for treatment strategies --
be they behavioral, medical, or surgical," he says.

Wang and colleagues report their findings in the Feb. 15 issue of the
journal NeuroImage.

By Daniel DeNoon
Reviewed by Louise Chang
©2005-2006 WebMD, Inc. All rights reserved