A new study finds that air pollution could lead to increased rates of obesity. In the experiment, mice who breathed clean air were less likely to gain weight and were fitter than mice in an environment where the air was polluted.
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Laboratory mice offered some of the earliest concrete clues that the effects of air pollution may penetrate far beyond the lungs. Their breeder at the Ohio State University, Qinghua Sun, had been interested in studying why city-dwellers seem to be at a particularly high risk of heart disease compared to country folk. Lifestyle, of course, could be one reason: in most major cities a fast food chain is rarely more than a block away, for instance, which might encourage unhealthy eating. Nevertheless, he wondered if another answer may be hanging, invisibly, in the air we breathe.
To find out more, he started to raise laboratory mice in the kinds of conditions you might find across various cities. Some breathed filtered, clean, air, while others were funnelled the kinds of fumes you might find next to a motorway or busy city centre. Along the way, his team weighed the mice and performed various tests to study how their metabolism was functioning.
After just 10 weeks, the effects were already visible. The mice exposed to the air pollution showed greater volumes of body fat, both around the belly and around the internal organs; at the microscopic level, the fat cells themselves were around 20% larger in the mice inhaling a fine mist of pollutants. What’s more, they seemed to have become less sensitive to insulin, the hormone that signals to cells to convert blood sugar into energy: the first step towards diabetes.