In Search Of A Healthy Gut, One Man Turned To An Extreme DIY Fecal Transplant (theverge.com)
Josiah Zayner writes: Arielle Duhaime-Ross at The Verge followed Dr. Josiah Zayner, a former Scientist at NASA turned BioHacker, as he attempted the first ever full-body microbiome transplant. She writes "Over the course of the next four days, Zayner would attempt to eradicate the trillions of microbes that lived on and inside his body -- organisms that helped him digest food, produce vitamins and enzymes, and protected his body from other, more dangerous bacteria. Ruthlessly and methodically, he would try to render himself into a biological blank slate. Then, he would inoculate himself with a friend's microbes -- a procedure he refers to as a 'microbiome transplant.'".
There are other ways to adjust the bacteria present, such as through diet.
That worked for me. A few years ago I bought a $39 yogurt maker from Amazon, and started eating a bowl fresh from the incubator every morning. As my gut bacteria changed, so did my appetite. I no longer craved sugar or other carbs, and started eating more fiber and veggies. I guess the little critters were using some sort of chemical feedback to make me eat a diet more to their liking. I am about 5 pounds lighter, have more energy, and have had no gut problems (diarrhea, constipation, or pain) in years.