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.
The 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.
But 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.
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