Have you ever noticed that people who smoke seem skinnier than those who don’t?  And that one of the top complaints for many who quit smoking is that they’ve gained weight?

Behavioral neuroscientist Marina Picciotto of Yale University decided to find out if there is an actual connection between smoking and body weight.  Her recent research reveals how nicotine works in the brain to suppress smokers’ appetites.

Researchers have found that nicotine can bind to receptors in the brain, which trigger various physical reactions such as the addiction to smoking,  increasing blood pressure or giving the smoker a feeling of relaxation.

While it’s known that nicotine causes a decrease in appetite, scientists have long suspected that this reaction worked through the receptors that were associated with reward and behavior reinforcement, since the brain looks at both cigarettes and food to be rewards. But, Picciotto’s new findings suggest that appetite has its own pathway.

The research team focused on one particular nicotine receptor, dubbed α3β4, which is said to have antidepressant effects on mice.  After giving their test mice drugs designed to specifically stimulate only the a3β4 receptors, team members noticed a unique side effect of the drug; the mice were eating less than half the amount of food as untreated mice.

The team went on to find that nicotine does, in fact, bind to the α3β4 receptors, which in turn tells the brain that the subject’s appetite was satiated and that this reaction is virtually indistinguishable from the signal the brain processes after eating a large meal.

As a result, the team found that the body fat of the test mice dropped from between 15 percent to 20 percent over 30 days.

Although the scientists primarily studied male mice for this study, past research shows that females tend to experience larger weight loss when they start smoking and gain a larger amount of weight if they quit.

This anomaly has the research team wondering if this means that the nicotine could be working through an additional, hormone-regulated pathway in the female brain that has yet to be discovered.

Picciotto says her group is repeating the experiments this time on female mice.  The study was recently published online in the journal Science.