Well Debbie, that is kind of a two answers question.
With my IBS, I noticed a difference almost immediately. Although I have to be totally honest > few people on this forum probably eat half as bad as I did, before I started this whole thing !
That said, going from a 3000-4000 cal nightly food binge (on top of the other 3000-4000 cals a garbage food I had eaten throughout the day) of fast food, pizza, processed crap, etc, >>>>> to a bowl of bran flakes with 1% milk and strawberries, REALLY helped to straighten out... er, at least, empty out my stomach, in maybe as little as a week.
I still had bouts of constipation, followed by diarrhea, but in between all of that, my stomach felt much better.
So anyway, it took probably 12 months to get my stomach completely straightened out, even though I was way better, in only a few months.
Nowadays, even as much as I eat (4000 cals a day, with a lot of low cal bulky stuff included) I still only go once a day, and usually feel completely emptied, and ready to rock ! :)
Now with my Fibro, it was definitely a more gradual thing. I'd say it took 12-18 months, to get to the 90-95% remission level I am now. Also, working out like I do, I develop plenty of aches and pains "naturally". So sometimes I would have to stop and consider, that maybe some of these aches and pains had an actual explanation, other than Fibro.
But that's okay, as I have said before, for whatever weird reason, it seems as though the more soreness, and / or natural aches and pains I can give my body to deal with, the more side tracked my Fibro becomes. It's like my body seems to be too busy dealing with "actual" issues, to be making up any issues on its own....
Of course the side effect is, I'm looking better, and feeling better about myself all the time :)
Kinda' sorta' starting to feel like I can call myself a beginning body builder now :) LOL Long ways to go, but I don't plan on quiting anytime soon.
Peace,
Fish