A recent research that studied the brain scan of some obese people reported that obese people might get addicted to food in the similar fashion as a drug addict to drugs.
Gene-Jack Wang and colleagues at Brookhaven National Laboratory in New York conducted this study. It was published in the October 17, 2006 issue of the Proceedings of the National Academy of Sciences and online in PNAS Early Edition the week of October 2.
"This study opens new territory in understanding how the body and brain connect to each other, and how this connection is tied to obesity," said lead author Gene-Jack Wang.
"We were able to simulate the process that takes place when the stomach is full, and for the first time we could see the pathway from the stomach to the brain that turns 'off' the brain's desire to continue eating."
The study was conducted on 7 obese people who had gastric stimulators implanted for 1-2 years. This device gives a low-level electrical stimulation to the vagus nerve. The device in 'on' position stimulates the vagus nerve making the stomach expand and generate peptides that sends a message of "fullness" to the brain.
"We know that if we eat, our stomach sends a signal to the brain via the vagus nerve. The ingredients of food touch the wall of the stomach and the signal goes through to the brain to say 'eat more' or 'eat less'," explained Wang. "But we wanted to know which area of the brain the signal goes to," he said.
In order to monitor the brain metabolism, the participants were injected with radioactive glucose. They were subjected to 2 separate positron emission tomography (PET) brain scans two weeks apart: one with the gastric stimulator on, the other with the stimulator off.
"We found that implantable gastric stimulators induced significant changes in metabolism in brain regions associated with controlling emotions, effectively shutting down these obese subjects' desire to eat," said Wang.
Hippocampus region of the brain showed significant changes. There was an 18% increase in metabolism during gastric stimulation. The activation of this area is similar to that seen in drug addicts when they crave for cocaine.
"It (The hippocampus) is the area related to memory and the reward system. The areas lighting up were areas activated in drug addicts. It's very similar to what triggers the craving for cocaine," said Wang.
"So despite receiving the "full" signal, they still have the craving for more. The findings help explain why it is so difficult to retreat from obesity. We now know the decision to eat involves emotions and the cognitive system too. This study shows how the brain tries to manipulate the body and not the other way around," Wang noted.
"It is difficult for obese people to diet because they can't suppress the craving to get their next "fix" even when physiologically, they're getting a "full" signal from the stomach," the researcher added.
"Such people may continue to feel hungry, even when they have eaten an amount that would satisfy the hunger of a healthy person."