Pollution could be disrupting your weight-loss plans: laboratory rats who breathed in Beijing’s highly polluted air gained weight and experienced cardiorespiratory and metabolic dysfunctions after only 19 days of exposure, finds a new study funded by various Chinese government agencies. Researchers placed pregnant rats and their offspring in two chambers, one exposed to outdoor Beijing air and the other containing an air filter that removed most of the air pollution particles. After only 19 days, the lungs and livers of pregnant rats exposed to the polluted air were heavier and showed increased tissue inflammation. These rats had 50 per cent higher low-density lipoprotein (LDL, or “bad”) cholesterol; 46 per cent higher triglycerides, a type of fat in the blood; and 97 per cent higher total cholesterol. Their insulin resistance level, a precursor of Type 2 diabetes, was higher than their clean air-breathing counterparts. All these changes, known as metabolic dysfunctions, may lead to obesity. “Since chronic inflammation is recognised as a factor contributing to obesity and since metabolic diseases such as diabetes and obesity are closely related, our findings provide clear evidence that chronic exposure to air pollution increases the risk for developing obesity,” says Junfeng Zhang, a professor of global and environmental health at Duke University in North Carolina, US, and a senior author of the paper. The pollution-exposed rats were significantly heavier at the end of their pregnancy even though the rats in both groups were fed the same diet. Similar results were shown in the rat offspring, which were kept in the same chambers as their mothers. The negative effects of air pollution, however, were less pronounced after three weeks than they were at eight weeks. At eight weeks old, female and male rats exposed to the pollution were 10 per cent and 18 per cent heavier, respectively, than those exposed to clean air. Long-term exposure may therefore be needed to generate the continuous inflammatory and metabolic changes that ultimately increase body weight, the researchers say. The results of this study are consistent with other studies that show air pollution induces oxidative stress and inflammation in the organs and circulatory system. The findings also echo previous studies linking air pollution with increased insulin resistance and altered fat tissue. “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 Zhang. The study appears in the March issue of the Journal of the Federation of American Societies for Experimental Biology (FASEB). It was funded by several Chinese government agencies, including the National Natural Science Foundation of China, the Open Fund of the State key Joint Laboratory of Environmental Simulation and pollution Control, and the China Postdoctoral Science Foundation.