I purposely picked 1-2 days as a sweet spot educated guess. Too little time fasting might not be enough time to see symptoms improve, too much time fasting might cause ME symptoms to get worse.
I can't do a 2-day fast but intermittent fasting (8 hour feeding window) improves my brain fog and lactic acid feeling in my muscles. I can concentrate much better in the morning so i do the things i need to do before my first meal. After that i'm totally useless again.
I'm severely underweight and the intermittent fasting doesn't help that way but at least it helps my cognitive function for a part of the day.
I admit that I haven't tried fasting for quite a few years, but when I did fast for five days, it just avoided the flare-ups I'd gotten from foods. The baseline symptoms remained, and the flare-ups returned as soon as I broke my fast.
So, no benefit...and it really wasn't a lot of fun.
If you like Youtube, check out Butter Bob Briggs. He's my favorite carnivore and low-carber of all time. He does I.F. and he's just a cool dude.
With my hormones fasting was insane - and terrible - never again. BUT... my husband tried intermittent fasting and he has stuck with it and lost 40lbs last year. He did it slightly more sane then me. He fasts until noon, has a Soylent and then comes home and has supper. One meal a day.
The fasting kinda helped at first because it spikes cortisol / adrenaline, but after that wore off I Felt like crap. Fatigued AND hungry.
I have not tested this in years, but I used to get worse for about a day of fasting, then stabilise for a bit, then improve for about a day, then it takes a while for that to decline. Its not a huge improvement though, but it is noticeable.