New York, Nov 5 (IANS): Debunking a long-held popular belief that smoking cigarettes helps keep one slim, researchers have now found that even second hand exposure to cigarette smoke can cause weight gain.

"For people who are in a home with a smoker, particularly children, the increased risk of cardio-vascular or metabolic problems is massive," said Benjamin Bikman, author and professor of Physiology and Developmental Biology at the Brigham Young University (BYU), Utah in the US.

For the study, researchers exposed laboratory mice to second-hand smoke and followed their metabolic progression.

Those exposed to smoke put on weight.

The researchers found 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 Paul Reynolds, co-researcher from BYU.

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