The researchers will test the participants' glucose tolerance, the time it takes for digested food to transit through the intestinal tract, and the amount of calories in the patients' stool.

CNN: Can you smell obesity?

It's also possible, says Mathur, that the release of methane slows the transit of digested food through the intestinal tract, and that could increase the time for additional calories from digested food to be absorbed and added to the body's tally.

CNN: Can you smell obesity?