Taruni Gandhi|M4PNews, Chandigarh
Take a deep breath, and exhale. Yes its Air that makes you fat. Depending on where you live, that life-giving lungful of air might just be pushing you towards diabetes and obesity.
Two people can eat the same foods, and do the same exercise, but one may put on more weight thanks to the air around their home. The idea that “thin air” can make you fat sounds ludicrous, yet some extremely puzzling studies appear to be showing that it’s possible. Two people can eat the same foods, and do the same exercise, but over the course of a few years, one may put on more weight and develop a faulty metabolism – thanks to the atmosphere around their home.
Traffic fumes and cigarette smoke are the chief concerns, with their tiny, irritating particles that trigger widespread inflammation and disrupt the body’s ability to burn energy. While the short-term effects are minimal, over a lifetime it could be enough to contribute to serious disease – besides the respiratory illnesses more commonly associated with smog.
“We are starting to understand that the uptake and circulation of air pollution in the body can affect more than just the lungs,” says Hong Chen, a researcher at Public Health Ontario and the Institute of Clinical Evaluative Sciences in Canada.
How strong is the evidence from these studies, and should you be concerned?
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.
The exact mechanism is still debated, but subsequent animal experiments suggest the air pollution triggers a cascade of reactions in the body. Small particles, less than 2.5 micrometres wide, are thought to be primarily to blame – the same minuscule motes of pollutant that give city air its gauzy haze. When we breathe in, the pollutants irritate the tiny, moist air sacs that normally allow the oxygen to pass into the blood stream. As a result, the lungs’ lining mounts a stress response, sending our nervous system into overdrive. This includes the release of hormones that reduce insulin’s potency and draws blood away from the insulin-sensitive muscle tissue, preventing the body from tightly controlling its blood sugar levels.