to me it sounds like the guy lost good gut bacteria, and yeast/candida remained, and now hes just a fermentation vat for various refined sugars and starches
i researched it more
it is because gut bacteria get messed up and fungal (yeast) overgrow because of it and ferment sugars and starches in the gut
taking high quality prebiotics, digestive enzymes and probiotics will restore gut health and balance
avoiding all refined carbs is necessary while doing this else the candida wont be reduced in population
they’ve done fecal transplants to cure someone of this, which is another way of getting good bacteria back into the gut system. but you’d still have to avoid refined carbs in order for you not to keep fueling the yeast population.