I've heard of FMT used in treating illnesses. I wonder what the criteria would be for weight-loss.

I'm sure there's a lot more science to this than just scavenging the microbiome of a thin person. 

By the way, this is still an emerging science, so there remains a lot to be figured out. 

http://pandawhale.com/post/50175/when-feces-is-the-best-medicine-by-amanda-schaffer-in-the-atlantic

Still, this sounds promising:

It's not the most pleasant treatment you can imagine, but there's strong evidence that faeces is good for the microbiome environment inside our guts. Reports have shown that in some situations, poop pills are actually more effective than antibiotics, and now there's some strong demand for healthy body waste if you're interested in parting with some for a bit of cash.

The controlled, randomised trial starting this year will be run by researchers at the Massachusetts General Hospital. Based on research that suggests bacteria from donor excrement can fight infections that have become rooted in the digestive system of the recipient, they'll be testing if poop pills could be a viable treatment option for weight-loss in the future.

"Faecal microbiota transplantation (FMT) transfers intestinal bacteria by a 'stool transplant' from a healthy, lean person to a person with obesity," the researchers explain.

Poop samples from lean and healthy donors will be freeze-dried and then given to 21 obese patients during the course of the trial.

There's a growing belief that this kind of treatment could help with weight-loss and various other metabolic disorders, but so far we only have a few animal studies and some anecdotal evidence in humans to go off. This new study should give us much more information about the potential of the humble poop pill.