Nicola Jones, reporting for Nature News on another medical finding involving gut bacteria:
People who have had bypasses are known to experience changes in the selection of microbes in their guts. Fat people have been shown to host a different selection of gut bacteria from people who are obese, and transferring the gut bacteria of fat mice into thin ones can cause the thin mice to pack on extra weight. But no one knew whether the microbes in bypass patients changed because they got thin, or if the patients got thin because the microbes changed.
Now, the study in question only looked at mice, and the results of mouse studies don’t always carry over into humans. Still, it’s promising.