It's less obvious, but it's also not such a stretch to imagine mechanisms for positive feedback, in which some of these bacteria reinforce chemical signals that lead to consumption of more of the food they thrive on.
In addition a similar study has been tried on genetically identical twins. The difference being the bacteria.
How someone cultivates these bacteria, still a mystery. It could be antibiotics as much as potato starches.
Which is weird, because:
> "The researchers found the strongest links with visceral fat, participants with a high diversity of bacteria in their faeces had lower levels of visceral fat."
A stool sample decreasing biodiversity sounds counter-intuitive to me
Also, diversity has "the strongest links with visceral fat", it isn't the only parameter linked with obesity (visceral or not).
If so, this would be consistent with increased biodiversity (from the stool transplant) correlating with reduced visceral fat.
At any rate, the interaction is probably more complex than our current understanding, as this is a very new area of research.
Can you provide any links for this FMT screening process?
Anything that improves the state of the colon for a person with IBD/Crohn's/UC will cause a massive weight change. A few years back I had 30 cm of small intestine removed and promptly gained 20 kg in two months (which was a very good thing for me then). That obviously won't happen to someone normal.