Okay so this evidence is both anecdotal and with some evidence. My personal story is I got IBS after a sepsis and it was hard, I had back pain and medication didn't help the symptoms. I got really fed up and tried a keto diet, after I heard a theory that diet could affect auto immune disorder and conditiona after watching mikala Peterson. I tried a keto diet and to my surprise my symptoms left within a week with my first flare up 18 months later after eating a heavily carb diet on holiday.
I would give this diet a go because it's been changing for me.