A new study suggests that exposure to air pollution increases the risk for obesity and diabetes, UPI reports.

Researchers at Duke University exposed lab rats to the highly polluted air of Beijing and found that the air caused metabolic dysfunction in the exposed rats, leading to obesity and precursors of obesity. No such symptoms were observed in rats that were not exposed to the polluted air.

"If translated and verified in humans, these findings will support the urgent need to reduce air pollution, given the growing burden of obesity in today's highly polluted world," Junfeng Zhang, a professor of global and environmental health at Duke University, said in a press release.

The study was published in the FASEB Journal.

The study showed that after 19 days of exposure to unfiltered air, rats had 50 percent higher bad cholesterol levels, 46 percent higher triglycerides, and 97 percent higher total cholesterol, as well as a higher insulin resistance level.

The exposed rats also gained more weight eight weeks into the study, with female rats 10 percent heavier and male rats 18 percent heavier than their counterparts breathing clean air.

"Since chronic inflammation is recognized as a factor contributing to obesity and since metabolic diseases such as diabetes and obesity are closely related, our findings provide clear evidence that chronic exposure to air pollution increases the risk for developing obesity," Zhang said.

China called two red alerts in two weeks in 2015 because of the especially poor air conditions.