The same brain circuits are involved when obese people fill their stomachs as when drug addicts think about drugs, a finding that suggests overeating and addiction may be linked, United States researchers reported on Monday.
The finding may help in creating better treatments for obesity - a growing problem in the United States and elsewhere.
"We wanted to know why, when people are already full, why people are still eating a lot," said Dr Gene-Jack Wang of Brookhaven National Laboratory in Upton, New York.
"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," reports Independent Online.
According to Reuters, Wang and colleagues tested seven obese volunteers who had been fitted with a gastric stimulator -- a device that tricks the body into thinking the stomach is full, a state known as satiety.
They used a positron emission tomography or PET scan to see which parts of the brain activated when the stimulator was activated. They also carefully questioned their volunteers, all of whom were very obese, about why and when they overate.
"We thought the activated area (of the brain) must be in the satiety center, which we learned in medical school is supposed to be in the hypothalamus," Wang said in a telephone interview.
"We saw a lot of activity in all areas of the brain, especially in the hippocampus. That region is related to learning, memory and is also related to a lot of things such as sensory and motor impulse and emotional behavior," Wang said.
Writing in the Proceedings of the National Academy of Sciences, Wang and colleagues said the hippocampus was 18 percent more active when the gastric stimulator was on.
How can the information be used to help people avoid excess weight? "That is the million-dollar question," Wang said. "We must study to learn more about how the signal is transmitted and how to treat obesity. As with drug addiction, we might also have to treat the emotions."
We should be able to identify sites within the stomach that are most likely to reduce hunger and appetite or induce a sense of fullness, either of which would be a novel alternative."
But "eating behavior is so complicated," Wang added. "Even if you are under stringent circumstances, you must eat," reports HealthDay News.