Apparently Nicotine does more than hook smokers - it also makes them gain weight when they quit.  A new research study sheds light on one of the most talked-about side effects of quitting smoking.

It turns out that nicotine can rev up brain cells that normally signal people to stop eating when they're full, researchers report in Friday's edition of the journal Science.

The weight connection isn't huge: On average, quitters gain less than 10 pounds. Still, it's a worry that many smokers cite when asked why they don't try to quit. Now the question is whether the discovery might lead to better treatments to help them quit without worrying about weight.

Nicotine hooks onto a variety of receptors, or docking sites, on the surface of cells. That's how it triggers addiction in one part of the brain.

But when it comes to weight, the Yale research found that both nicotine and the related drug cytisine were activating a different receptor than the one involved in addiction. This one is located on a small set of neurons in the hypothalamus, a region that regulates appetite.

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