Gut Bacteria Is Making You Fat But so are all those Big Macs By Kevin Spak, Newser Staff Posted Jun 26, 2010 11:10 AM CDT 26 comments Comments That belly probably has some unfortunate bacteria in it. (Shutterstock) (Newser) – Your ill-considered Cheetos-and-bacon diet isn’t the only reason you’re fat. Scientists believe that advanced networks of bacteria and other microbes in our intestines and colons have an incredible influence on obesity, the LA Times reports. These 10 to 100 trillion little guys work together almost like an organ, determining, among other things, how many calories we absorb and whether we make or burn fat. Scientists have definitely discovered a link between gut bacteria and weight in mice, but in humans the research is just fuzzy enough to prevent some companies from labeling their bacteria-rich goods as weight loss products. But the scientists are fairly sure the link is real, and that increased antibiotic use, improved hygiene, and other such advances, which can change the bacteria we carry, are contributing to the obesity epidemic.