Brain circuitry linked to obesity

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ANN ARBOR, Mich., Aug. 7 (UPI) -- The weight-loss effect of leptin, a hormone produced by fat tissue, has been linked to higher levels of the brain chemical dopamine, U.S. researchers said.

The animal studies, published in Cell Metabolism, found neurons with receptors for the hormone leptin exist in many parts of the brain -- not just the area controlling satiety.

Martin Myers Jr. of the University of Michigan in Ann Arbor says rat studies suggest that in addition to the area controlling the feeling of fullness after eating, leptin also affects other brain sites of action for drugs of abuse -- as well as for control of motivation for food or sex.

While higher dopamine release tends to be associated with wanting things -- food or something else -- he suspects in this case higher dopamine at baseline may work to dampen the response to food temptations, making food easier to resist.

"Some people may over-eat rewarding food because of a perceived 'reward deficit,'" Myers says in a statement. "When leptin is turned up, it might fix that deficit and make us feel better about a lot of things."