Craving Chocolate? Blame It On Your Brain

ANN ARBOR, Mich.Scientists have discovered an opium-like chemicalenkaphalinproduced naturally in the brain is a mechanism that generates intense motivation to overeat tasty foods, such as chocolate, according to a new study published in the journal Current Biology.

The neostriatum, located near the middle and front of the brain, has traditionally been thought to control only motor movements; however, for several years, it has been known that the neostriatum is active in brains of obese people when viewing or tasting foods, and in brains of drug addicts when viewing photos of drug-taking.

Researchers at the University of Michigan found when they gave extra morphine-like drug stimulation to the top of the neostriatum in rats, it caused the animals to eat twice the normal amount of sweet fatty food. For this study, that food was M&M milk chocolate candies.

"The same brain area we tested here is active when obese people see foods and when drug addicts see drug scenes," said Alexandra DiFeliceantonio, a doctoral student in psychology and the study's lead author. "So it seems likely that our enkephalin findings in rats mean that this neurotransmitter may drive some forms of overconsumption and addiction in people."

For the study, researchers measured levels of enkephalin using a painless microdialysis probe while rats were allowed to eat as much chocolate as they wanted. They found that enkephalin levels surged dramatically as soon as the rats started to eat, and remained high as long as they ate. When researchers gave a painless microinjection of an opioid-stimulating drug in the rats' neostriatum, the rats ate double the amount of chocolate. The researchers mapped where extra drug stimulation of opioid receptors affected eating habits. They found overeating was only caused in one region at the front and center part of the neostriatum .

Finding the brain mechanisms for overconsumption is a step toward designing better biological-based treatments for obesity and binge eating disorders," they said.