Obese woman outdoor
Breathing polluted air can lead to weight gain. Istock

Over the past few years there has been plentiful proof that air pollution leads to respiratory and cardiovascular diseases. Now, scientists say they have found evidence that breathing highly-polluted air could also increase risks of metabolic dysfunction and lead to weight gain.

Scientists from the University of Duke, in the US, used a rodent model to come up with these conclusions. During three weeks, they exposed pregnant rats and their offspring either to unfiltered Beijing air or to clean, filtered air.

Beijing air pollution

Beijing is one of the most polluted city in the world. In recent months, it has made the headlines multiple times after thick smog engulfed the Chinese capital.

In December, more than 22 million inhabitants of the city were warned to stay indoors and levels fine particles PM2.5, which pose the greatest health risks, reached unprecedented levels.

Scientists believe the air pollution in China is responsible for many cardiovascular and respiratory diseases, and for at least 1.5 million deaths each year.

Epidemiologic evidence suggests that air pollution is a risk factor for childhood obesity, but up to now, there had been little data to prove that a link did exist between air pollution and non-diet-induced weight increases.

At the end of this experiment though, the scientists found that both parents and baby rats exposed to polluted Beijing air were significantly heavier than their counterparts who had breathed the cleaner, filtered air.

Adult male rats breathing polluted air weighted 18% more than other rats, while female rats weighted about 10% more.

Combat obesity and pollution

To explain these weight differences, the study, published in the Journal of the Federation of American Societies for Experimental Biology, shows that the rats exposed to unfiltered air were more prone to inflammations and lipid activation in the lung, as well as increased tissue and systemic oxidative stress. According to the scientists, this then leads to metabolic dysfunction, and to the weight gain observed both in the adult and the baby rats.

More research is needed to determine how far these results are applicable to humans. However, scientists say that, because of the global obesity epidemic, their conclusions do still provide compelling evidence of the need to accelerate the fight against air pollution.

"These findings will support the urgent need to reduce air pollution, given the growing burden of obesity in today's highly polluted world", they concluded in a statement.