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    Brain Differences Seen in Obesity-Prone Rats May Be Linked to Fullness Hormone Leptin

    Feb. 5, 2008 -- Obesity isn't just about eating habits; it may also have genetic roots in the brain.

    New research on obesity shows brain differences between rats that are genetically prone to becoming obese and rats without that obesity tendency.

    The differences are in part of the hypothalamus, which is a brain region that's involved in appetite and hunger.

    In rats that are genetically prone to obesity, certain brain cells in the hypothalamus don't grow as much and are less sensitive to the fullness hormone leptin, compared with other rats.

    Those patterns may gear those rats toward obesity, note the researchers, who included Sebastien Bouret, PhD, of the University of Southern California.

    "It seems [in the case of these rats] that appetite and obesity are built into the brain," Bouret says in a news release.

    That may mean that those rats would have to work harder not to become obese, because their brains might not get the "I'm full, stop eating" signal from their bodies.

    But that doesn't mean that obesity is a done deal for those rats. Bouret's team didn't put the rats on running wheels or make them diet to see if that would counter their obesity inclination. And the findings don't mean that obesity is just about the brain or genes. Behavior counts, too.

    "It is increasingly accepted that obesity results from a combination of genetic and environmental factors," Bouret and colleagues write in February's edition of Cell Metabolism.

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