Second-hand smoke could make you fat

Smoking is not slimming

Challenging the decades-old belief that smoking cigarettes keeps you slim, a Brigham Young University study found that exposure to cigarette smoke can actually cause weight gain. But here's the kicker: Second-hand smoke is the biggest culprit.

"For people, particularly children, who are in a home with a smoker, the increased risk of cardiovascular or metabolic problems is massive," said author Benjamin Bikman, professor of physiology and developmental biology at Brigham Young University.

RELATED: Even light smoking doubles risk of cardiac arrest

Why second-hand smoke causes weight gain

Bikman and BYU colleague Paul Reynolds exposed lab mice to side-stream (or second-hand) smoke and followed their metabolic progression. Sure enough, those exposed to smoke put on weight.

When they drilled down to the cellular level, they found the smoke triggered a tiny lipid called ceramide to alter mitochondria in the cells, causing disruption to normal cell function and inhibiting the cells' ability to respond to insulin.

"The lungs provide a vast interface with our environment and this research shows that a response to involuntary smoking includes altering systemic sensitivity to insulin," Reynolds said. "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."

It’s a good reason to avoid spending time with smokers but what about the smokers?

"They just have to quit," Bikman said. "Perhaps our research can provide added motivation as they learn about the additional harmful effects on loved ones."

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