US scientists have figured out exactly how nicotine acts as an appetite suppressant in the brain, a finding that could one day help in the fight against obesity, researchers say.

Smokers tend to be thinner than people who don't smoke, and the study led by Yale University and published in the journal, Science, describes how nicotine activates certain neurons in a part of the brain called the hypothalamus.

"Many people say they won't quit smoking because they'll gain weight."

Those neurons tell the body when it's had enough to eat, according to senior author Marina Picciotto, a professor of neurobiology and pharmacology at Yale.

"Many people say they won't quit smoking because they'll gain weight.