Agreed it's probably too early. I'm looking at a startup that claims it can induce weight loss by altering the microbiome for example.
I don't think there is any doubt that you could potentially induce weight loss by altering the microbiota--the reverse has clearly been demonstrated: fecal microbial transplants from overweight people into thin people have induced an overweight phenotype, I see no reason why the opposite couldn't be true.
However, the problem is that they would need to build a "defined composition" microbial transplant and we have nowhere near enough data to do so today.
[I am working on C difficile right now so all of this is very fresh in my mind]