I've been reading about this for a while (and I didn't do a great job of collecting my sources to link here) but from what I understand as a layman, truly changing the composition of the gut involves killing the current population, transplanting a new population in from a healthy host (person, mouse, whatever species you're working with) and then suppress the immune system while the new population takes hold. It's dangerous because of the immune suppression, but the outcomes in mouse populations (and in extreme cases where they actually do it in humans) are incredible.
There are less invasive methods being practiced that just involve putting a healthy gut population into a human's gut, and from what I've read it's still in the research phase.
Evidence of curing obesity, curing IBS in mice. I haven't seen any studies that are statistically significant in humans yet, because this is still relatively new.
There has also been some really interesting study of the brain-gut connection and the effect this microbe population has on mental health. Really interesting things where mice with aberrant gut microbiomes have "metal health conditions" (how ever you measure that in mice) and then have their vagus nerve (gut to brain, a huge nerve) cut. The outcomes were shocking, basically a curing of the condition. There is research here about humans:
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC9685564/
"metal health conditions" (how ever you measure that in mice)
I know cortisol levels are a way one can diagnose stress/anxiety in animals. (My vet said they look to that as a proxy for "is my animal in discomfort" at times)
There are less invasive methods being practiced that just involve putting a healthy gut population into a human's gut, and from what I've read it's still in the research phase.
Evidence of curing obesity, curing IBS in mice. I haven't seen any studies that are statistically significant in humans yet, because this is still relatively new.
https://my.clevelandclinic.org/health/treatments/25202-fecal...
There has also been some really interesting study of the brain-gut connection and the effect this microbe population has on mental health. Really interesting things where mice with aberrant gut microbiomes have "metal health conditions" (how ever you measure that in mice) and then have their vagus nerve (gut to brain, a huge nerve) cut. The outcomes were shocking, basically a curing of the condition. There is research here about humans: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC9685564/