The problem with this emerging theory about bacteria in the Gut modulating mood, obesity, etc. is very hard to be proved in an absolute way. The number of bacteria's in the gut is extremely high. I think we need much more research on the topic to be absolutely sure we know what we're talking about.
There is a growing awareness about probiotics, but most of the studies I read are not convincing enough, as of today.
(my description might be wrong) They start with a prediction; they modify mice and show that prediction is true; they then find human samples (staff and patients at an inpatient ED unit) and they find the staff don't have the particular gut flora while patients do. It's going to be really hard to get ethical approval to give the gut flora to healthy people - to give those people anorexia, so there is a missing step.
There is a growing awareness about probiotics, but most of the studies I read are not convincing enough, as of today.