A new study has revealed that exposure to cigarette smoke can actually cause weight gain, secondhand smoke being the biggest reason.

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

The researchers wanted to pinpoint the mechanism behind why smokers become insulin resistant and to find out the implications of smoke on metabolic function, they exposed lab mice to side-stream (or second-hand) smoke and followed their metabolic progression.

It was found that those mice that were exposed to smoke put on weight and when the 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 scientists said that 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. 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.

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