Could the answer to obesity be right under our (wrinkled) noses? A September 2013 study published in the journal Science demonstrates that the ability to prevent obesity might be hiding in the intestines of skinny people. The proof is in the poopy.Researchers from the Center for Genome Sciences and Systems Biology at the Washington University School of Medicine took stool samples from four sets of 20- or 30-something twins, each comprising one lean sister and one obese sister. The scientists then implanted bits of the samples into the intestines of lab mice, in a process called fecal transplantation. Though we think of feces as pure waste, to a scientist it can be a treasure trove of bacteria and chemicals that live in the gut and play important roles in a wide range of body functions from digestion to inflammation and obesity.MORE: A Surprising Cause of ObesityThe mice were fed the same diet of low-fat chow and ate the same amount. As expected, the mice that received transplants from obese donors quickly got fat, while those harboring the gut microbiota of thin twins did not. The results don’t surprise Michael Wald, M.D., a nutrition and integrative medicine specialist who has been a proponent of fecal transplants for a decade and a half and was not involved in this research. “We use probiotics to modify gut environment to affect various inflammatory modulators and cell signaling molecules to enhance metabolic rate,” all of which are involved in obesity. This is the same principle.Next, the research team took bacterial cultures from the poop samples, grew them in petri dishes and put them into a new set of healthy mice. They housed mice with the obesity bacteria in cages with lean-bacteria-carrying mice and waited. Mice are coprophagic, which is the clinical way of saying that they eat each other’s poop. The mice did as mice do, and the researchers noticed a remarkable trend. The mice that should have gained fat didn’t. Analysis of their gut microbiota after several days showed that it looked a lot like that of their lean-cultured cage-mates. Effectively, being skinny was contagious.MORE: How Probiotics Balance Gut BacteriaBut there was a twist. The transfer of bacteria that protected against obesity only worked when the mice were fed a diet low in fat and high in fruits and vegetables. When lean and obese mice were housed together and given high-fat, low-fruit diet, there was no change in the bacterial makeup; the mice with obese cultures gained weight.“Together, these results illustrate how a diet high in saturated fats and low in fruits and vegetables can select against human gut bacteria taxa associated with leanness,” the authors write. “…The stage is set for studies designed to determine which culturable components of a given person’s gut community are responsible [for body composition and metabolism].” From here, they posit that scientists may be able to figure out how to manufacture a treatment that doesn’t require actual, physical feces.The Promise of PoopIn the meantime, the only way is the old fashioned way: fecal transplants, or transpoosions, as they’ve been called. “There is no way they’re going to reinvent poop in the lab,” Wald asserts. “They can make something that has the basic components,” but it won’t have the biochemical nuances that make fecal transplants so effective against irritable bowel disease, a deadly antibiotic-resistant infection called C. difficile and a number of autoimmune disorders.Fecal transplants are still considered experimental and most doctors are wary of performing them. That’s why when he suggests fecal transplants to patients with ulcerative colitis, multiple sclerosis or cancer, Wald gives them an instructional pamphlet on how to do your own transpoosion at home. “Generally patients have to get poop from a relative, because genes that are closer might be a better fit. Research shows that stool from any seemingly healthy person works. You can even get it from a close friend, as disgusting as that sounds.” Disgusting indeed. But Wald swears that in his experience he can’t think of a single time a patient didn’t see improvement.A quick Google search will bring up directions from Wald and other pro-poop DIY-ers. (Materials list: 50 milliliters of someone else’s doody; 100 milliliters saline; home enema kit; blender.) While there’s a growing body of research on the potential benefits of fecal transplantation, its use for the treatment or prevention of obesity has not been tested in humans. But somewhere down the road, we could see scientists turning crap into gold.MORE: What Is IBS?