Living an overindulgent, couch potato existence certainly isn’t doing your waistline any favors but there may be other influences that are making you fat.Some scientists now believe that pollution may be at least partially to blame for the exploding obesity and type II diabetes epidemics.In a recent review paper published in the online version of Environmental Health Perspectives, Cornell University researchers raised the possibility that environmental pollutants may somehow affect microbes found in the gut. Although these digestive tract bacteria outnumber human cells by a factor of 10, their function largely remains a mystery.FIND OUT: Are You Obese? Measure Your Body HealthWe do know they play a key role in weight and insulin control and exposure to everyday pollutants like those found in plastics, pesticides and drinking water seems to wreak havoc on their ability to metabolize fat.According to Nikhil Dhurandhar, Ph.D., an associate professor at Pennington Biomedical Research Center in Louisiana and an obesity research pioneer, the mechanism for dysfunctional fat metabolism may differ depending on which chemical the gut microbes are exposed to. “In some cases a pollutant may cause them to increase fat storage, in other cases it may trigger overeating or affect energy regulation,” he notes.MORE: How The Environment Affects Your BeautyAnother theory is that the chemicals may interrupt critical periods of development during puberty, possibly increasing a predisposition towards weight gain and diabetes. The Cornell scientists point to research showing that exposure to a pollutant found in some paints, wallpaper, textiles and floor coverings has been linked to weight gain and higher insulin levels in male mice. Other persistent environmental baddies—such as insecticide DDT, dioxin and PCBs—have been tagged as likely culprits for upping the risk of type II diabetes.MORE: BPA: The Unfriendly, Everyday ChemicalMore than three dozen environmental chemicals have been identified as “obesogenic” or “diabetogenic” meaning they’ve been shown to impact metabolic pathways leading to obesity or diabetes. However, scientists like Dhurandhar suspect that the pollution theory is just the tip of the iceberg. “Both obesity and diabetes are probably influenced by multiple factors,” he says. “There are at least ten other candidates besides ‘the big two’, overeating and under-exercising, we believe could be involved. Pollution is just one.”Current estimates suggest that the costs associated with obesity alone exceed $160 billion annually and account for more than 16 percent of medical care costs in the United States. Nearly 10 percent of Americans have been diagnosed with diabetes. A cure or preventative vaccine for either is likely a long way off. So for now, the best defense remains eating less and moving more, and if you feel inspired to become an environmental activist, it might help the bigger picture.QUIZ: How Healthy Do You Feel?