A study just released in Science shows that mice that receive intestinal bacterial from fat people get fatter than mice colonized with gut bacteria from thin people. The results demonstrate how bacteria in the digestive tract affect body weight.
This relationship may not be too surprising if you have been following any of the latest research on the interaction between our microbiome--the roughly 5 pounds of bacteria and other microbes living in and on us--and our health. Until recently, medicine has largely ignored the influence our personal microbiomes have on our health. However, that view has turned around drastically as it has become clear that our wellbeing is linked with the complex ecosystem of critters that call us home.
The large diversity of bacteria living in the intestine seem to play a particularly important role in our health. A couple studies published last month analyzing intestinal bacterial in individuals in Denmark and France linked a low diversity of gut bacteria with obesity and metabolic syndrome. Now, the recent mouse study mentioned above helps establish that, in fact, the specific bacteria present in the gut can have a direct influence weight gain. Basically, human stool from obese and thin twins was inserted into sterile mice's digestive tracts to seed bacteria from each of these individuals. You can read more about the details of this recent work on the Real Clear Science website.
Probably one of the most dramatic demonstrations of the effect intestinal bacteria can have on health is the now well established fecal transplant treatment for life threatening antibiotic resistant Clostridium difficile bacterial infections. Yes, this is what is sounds like--transferring stool from a healthy individual's stool into a patient suffering from the infection.
Approximately 14,000 people a year die of "C. diff" infection, usually acquired in hospitals. Until very recently, the only treatment for this disorder entailed a few weeks infusion with broad spectrum antibiotics. In most cases, this approach was unsuccessful or led to several recurrences of the disease. However, almost unbelievably, fecal transplants cure about 90% of the patients with these infections.
The mouse obesity study essentially consisted of a fecal transplant into the mice. This seems to suggest fecal transplants might be a viable treatment for obesity too? Eew! Sometimes it's not so easy to follow the science.
You can read more about recent research on the importance of the microbiome and fecal transplants in the recently posted The Microbiome, Our Health, and Other Poop.