Weight gain has long been established to be affected by diet and physical activity but it looks like even the very air you breathe may be a factor in determining obesity risk.

In a study published in the Journal of the Federation of American Societies for Experimental Biology, researchers have showed that pregnant rats and their offspring exposed to highly polluted air in Beijing experienced metabolic and cardio-respiratory dysfunctions and gained weight compared to their counterparts exposed to filtered air.

Though the rats were exposed to polluted air for three to eight weeks, just 19 days were enough for increased tissue inflammations to be evident. Additionally, the group of rats exposed to polluted air had 97 percent higher total cholesterol level, 50 percent higher bad cholesterol and 46 percent higher triglyceride levels, not to mention higher levels of insulin resistance, which is a Type 2 diabetes precursor.

These results support the researchers' conclusion that exposure to air pollution leads to metabolic dysfunction, which is an obesity precursor. True enough; the rats exposed to air pollution were dramatically heavier than the clean air-breathing group, even though all the rats were on the same diet.

The results were applicable as well on rat offspring that stayed in the same chambers as their mothers.

The researchers have noted, however, that the bad effects of air pollution were less serious at three weeks than by the time the eight-week period of the study was over. This suggests that for metabolic changes to grow severe enough to increase body weight, long-term exposure to polluted air is necessary.

By the time they were eight-weeks-old, male and female rats exposed to polluted air were 18 and 10 percent heavier, respectively, compared to those breathing cleaner air.

The researchers' findings are consistent with results from earlier studies showing that air pollution promotes inflammation and oxidative stress in the body, increases insulin resistance and alters fat tissues.

"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," said Junfeng Zhang, the study's senior author.

Photo: David Barrie | Flickr

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