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, US researchers reported on Monday.

The finding may help in creating better treatments for obesity a growing problem in the US 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."

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.

They used a PET scan to see which parts of the brain activated when the stimulator was activated. "We thought the activated area (of the brain) must be in the satiety centre," Wang said. "We saw a lot of activity in all areas of the brain, especially in the hippocampus."

The gas stimulators also sent messages of satiety to brain circuits in the orbitofrontal cortex and striatum, which have been linked to craving and desire in cocaine addicts.

"This provides further evidence of the connection between the hippocampus, the emotions, and the desire to eat, and gives us new insight into the mechanisms by which obese people use food to soothe their emotions," said Wang.