It's very necessary to avoid processed foods/beverages, junk foods, refined sugar, animal fats, caffeine...it takes time for your body to adjust to eliminating those terrible things...my GI told me to take a fibre supplement daily for the rest of my life, it's done me wonders, I'm even able to tolerate eating fibreous foods without getting all gassy and bloated or pain...the trick with fibre is starting with a small amount and increasing slowly since fibre can initially cause gas and bloating even for healthy people...once your system adjusts then you slowly increase it with a small amount until you're satisfied with the results.
It takes time to retrain your body/system from eliminating bad/junky foods and beverages to eating healthy and adding fibre, drinking plenty of water is key which should be done for IBDers because of our higher risk of dehydration.
Healthy or ill, no one should over-do it with too much fibre.
My bum is broken....there's a big crack down the middle of it! LOL :)