For more than 50 years, Americans believed cigarettes kept you thin, but a new study has challenged the misconception and has actually found it does the exact opposite — cause weight gain. Research out of Brigham Young University has crushed the common misconception that cigarette smoking suppresses appetite and leads to weight loss. The findings of fattening secondhand smoke were published in the American Journal of Physiology: Endocrinology and Metabolism, with enough evidence to keep children from exposure.

“For people who are in a home with a smoker, particularly children, the increased risk of cardiovascular or metabolic problems is massive,” the study’s coauthor Benjamin Bikman, professor of physiology and developmental biology at Brigham Young University, said in a press release. “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 and his team exposed mice to secondhand smoke and watched how their little bodies reacted. They were about to analyze the metabolic functions that changed when exposed to the smoke, and as predicted, the mice gained weight. They suspected the smoke made the body insulin-resistant, which makes it difficult for the body to balance sugar levels in the blood, causing type 2 diabetes.

Secondhand smoking was the biggest offender. When researchers looked closer, they saw the smoke triggered ceramide, a small lipid that disrupts normal cell function. By turning off the ceramide, they were able to reverse the effects of secondhand smoke and were able to give the cells a healthy response to insulin. The scary part is when the mice were fed a high-sugar diet, the damage couldn’t be reversed, and the mice gained weight.

Could years of secondhand smoking have played a part in the current childhood obesity crisis in this country? More than one-third of children between 6 to 19 years old are overweight or obese, according to the Centers for Disease Control and Prevention. Young lungs living with smokers are inflicted with greater health risks, yet 20 percent are regularly exposed to secondhand smoke day in and day out.

It’s an oddity, considering the weight-loss angle has been a decades-old reliable marketing strategy for Big Tobacco. There was a myriad of outrageous advertising health claims, and some of them were even backed by physicians. One claim was cigarettes kept you thin and quitting them would cause you to replace the hand to mouth movement of placing a cigarette between your pursed lips with food.

Silva Thins, Stanford School of Medicine
Cigarette smoking medical misconceptions Silva Thins, Stanford School of Medicine

“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,” the study’s coauthor Paul Reynolds, professor of physiology and developmental biology at Brigham Young University, said in a press release. “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.”

They’re now searching for a way to block ceramide safely in humans, along with several other competing research teams. The team that can successfully and safely turn off ceramide is the team that has the power to reverse secondhand smoke effects. Smoking is a public health crisis — and has been for decades. Half of the U.S. population is exposed to secondhand cigarette smoke at least once a day, and 3,400 of them die every year because of it, according to the American Cancer Society.

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

Source: Bikman BT, Reynolds PR, Thatcher MO, Tippetts TS, Nelson MB, and Swensen AC, et al. Ceramides mediate cigarette smoke-induced metabolic disruption in mice. American Journal of Physiology: Endocrinology and Metabolism. 2014.