Exposure to air pollution raises the obesity risk, a new study found. The researchers discovered that the laboratory rats experienced weight gain and heart, lung, and metabolic problems just three to eight weeks after exposure to Beijing’s polluted air.

The study, to be published in the Journal of the Federation of American Societies for Experimental Biology (FASEB) in March 2016, involved leaving the pregnant rats and their offsprings in different chambers wherein one was exposed to Beijing’s air and the other was exposed to filtered air.

The researchers observed that the lungs and livers of those that were exposed to polluted air became heavier and experienced tissue inflammation after 19 days. They said that these rats had 97 percent higher total cholesterol, 50 percent higher LDL (low-density lipoprotein) cholesterol and 46 percent higher triglycerides. The researchers also noted that their insulin resistance level was higher than those that breathed the cleaner air, increasing their chances of developing type 2 diabetes.

Wikimedia/Jorge Royan

Wikimedia/Jorge Royan

These rats were given the same diet. The research team says that this study proves that air pollution causes metabolic dysfunction. This also reinforces previous studies that showed air pollution results in higher oxidative stress levels and inflammation as well as altered tissue and increased insulin resistance.

The researchers said that long-term exposure worsens the effects of air pollution. The changes observed after eight weeks were more noticeable than the changes noted at the third week of exposure. Moreover, when the offsprings reached the age of eight weeks, the females became 10 percent heavier and the males became 18 percent heavier than the offsprings that breathed filtered 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,” adds senior author Junfeng “Jim” Zhang, a professor of global and environmental health at Duke University. “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,” Zhang said.