ISME Journal. 1. Two independent facts from the experiment: A pathogen that causes obesity (in mice) seems to be active in some obese humans. 2. Severely restricted diet seems to powerfully reduce the population of this organism. I doubt that these facts are unrelated. It's classic host-parasite behavior. The pathogen depends on high calorie intake in its host, and therefore engineers that behavior (somehow). Further…
they have done studies though to see if doing a guy bacteria transplant from a healthy person to an obese person would change their weight, I believe there wasn't any difference found for weight loss but that there was some hope in using it as a treatment for diabetes. I'd have to look it up.
This particular study though I wonder if it was the calorie restriction, the weight loss or the content of the diet that caused the changes to happen.