The tiny microbes in our gut that feast on the food we eat as it moves through the digestion process have a powerful influence on our bodies. "Microbes have the capacity to communicate to the brain and influence behavior," Khoruts explains. For example, they send the signal for hunger and thus nudge us to eat more.
However, in people with prediabetes and type 2 diabetes, these microbes may have lost some of their ability to process certain foods. This could be due to larger societal shifts, in particular our use of antibiotics, which can kill some of the "good" bacteria and leave the remaining bacteria less able to do their work. Or, it may be that the food reaching our intestines doesn't need the final digestive action of these microbes because it is highly processed. In either scenario, the microbes continue to send hunger signals to the brain. This, in turn, may lead to overeating, obesity, and, eventually, type 2 diabetes.
By restoring a normal balance of bacteria in a patient's gastrointestinal tract, a fecal transplant may help prevent these false hunger signals. For the clinical trial Khoruts is leading, physicians will use fecal matter collected from a "champion" donor who has normal blood sugar levels and an ideal mix of gut microbes. This stool is then mixed with a saline solution and placed in the patient's intestine during a colonoscopy. After the procedure, participants receive 10 weeks of healthy meals developed by a dietician. Khoruts and his team believe the transplant and closely monitored diet will jump-start healthy processes in the guts of study participants and lead to better glucose regulation.