Secondhand cigarette smoke causes weight gain

Secondhand cigarette smoke not only increases the risk of cardiovascular and metabolic problems, it may also lead to gain weight, a new study has warned.

The study challenges the decades-old belief that smoking cigarettes helps keep you slim, researchers said.

Study author Benjamin Bikman, professor of physiology and developmental biology at Brigham Young University and colleagues wanted to pinpoint the mechanism behind why smokers become insulin resistant.

To carry out their study, they exposed lab mice to side-stream (or secondhand) smoke and followed their metabolic progression.

Mice exposed to smoke put on weight. When researchers 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," said BYU researcher Paul Reynolds.

"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," Reynolds said.

The key to reversing the effects of cigarette smoke, they discovered, is to inhibit ceramide. The researchers found the mice treated with myriocin (a known ceramide blocker) didn't gain weight or experience metabolic problems, regardless of their exposure to the smoke.

However, when the smoke-exposed mice were also fed a high-sugar diet, the metabolic disruption could not be fixed.

Bikman and his team are now looking for a ceramide inhibitor that is safe for humans.
"The idea that there might be some therapy we could give to innocent bystanders to help protect them from the consequences of being raised in a home with a smoker is quite gratifying," Bikman said.

The study is published in the American Journal of Physiology: Endocrinology and Metabolism.