It’s an old adage—smoking cigarettes makes you lose weight. A lot of people believe it, and many smokers refuse to quit afraid they’ll gain pounds, but a new study on secondhand smoke, may give them second thoughts.

The idea that smoking cigarettes can help keep you thin has been around for decades. As early as the 1920s Lucky Strike began pushing cigarettes as appetite suppressants with a clever ad campaign aimed at capturing the women’s market. The slogan: “For a Slender Figure—Reach for a Lucky Instead of a Sweet”. Some eighty years later, researchers at Yale University found that nicotine activates a pathway in the brain that suppresses appetite. But now comes a study that seems to challenge that.

A Brigham Young University (BYU) study published in the American Journal of Physiology: Endocrinology and Metabolism has found that exposure to secondhand smoke can cause weight gain.

"For people who are in a home with a smoker, particularly children, the increased risk of cardiovascular or metabolic problems is massive," said Benjamin Bikman, BYU professor of physiology and developmental biology, one of the study’s authors.

For their study, researchers exposed laboratory mice to second-hand smoke and followed their metabolic progression. Those exposed to smoke put on weight.

According to the researchers, the smoke triggered a tiny lipid called ceramide that leads to disruption of normal cell function by inhibiting the cells’ ability to respond to insulin.

"Once someone becomes insulin resistant, their body needs more insulin. And any time you have insulin go up, you have fat being made in the body," said co-author Paul Reynolds, BYU associate professor of physiology and developmental biology.

However, some experts would like a second opinion (or more) on the issue of second hand smoke and weight gain. They’d like to see more studies on the matter before deciding whether there’s a definitive correlation between the two.