Air pollution may contribute to obesity.

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Obesity is on the rise globally, and has been for years. There have been a lot of studies to try and figure out why that is. A new study may have some answers.

Researchers from Duke University and Duke Kunshan University found that diet and exercise might only be a part of the problem. According to an experiment carried out in Beijing, air pollution might be a significant contributor to obesity.

The researchers placed pregnant rats and their offspring in two chambers. One chamber was ventilated with outdoor Beijing air, and the other was ventilated with filtered air.

The rats exposed to pollution were much heavier at the end of their pregnancy than those exposed to filtered air, even though both groups ate the same diet. Their lungs and livers were also heavier. Similar results were shown in the rats’ pups, who stayed in the same chambers as their mothers.

The rats living in cages with outdoor Beijing air began to develop tissue inflammation, had 50 percent higher LDL cholesterol, 46 percent higher triglycerides, and 97 percent higher overall cholesterol than the rats breathing filtered air. They also had a higher insulin resistance level, a precursor to Type 2 diabetes.

The negative effects of air pollution increased with longer exposure, which suggests that the more polluted air the rats breathed, the more likely they were to have the metabolic and inflammatory changes needed to increase their weight.

In short, the rats living in the polluted air had many of the markers of obesity, and subsequently developed heavier weights than their peers.

Previous studies have also found this to be true.

“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,” says Junfeng “Jim” Zhang, senior author of the paper.