I would like to add a couple more things. I also love processed/fast/fatty food and still eat some in moderation! When really flaring - lots of blood and mucous - my NP told me to do the low fiber/low residue diet for a while when starting the meds. I honestly think the one thing that helped me most was Align probiotic. Many on here take other probiotics - I found Align to work for me. In three weeks my diarrhea stopped almost entirely although I still had some other symptoms.
I am not typical - because I am a senior - 69. I believe I cannot eat some of the things like others because of my IBS. For instance salmon makes me very sick and it is so good for most people. I do not have latose intolerance so a lot of my diet is cheese, lowfat milk, ice cream and yogurt. The promethius tests showed I do not have celiac disease and have no problems with gluten but I do have problems with whole wheat anything - I eat WHITE! See, what works for one does not work for everyone.
I typically eat white bread with natural peanut butter for breakfast, 1/2 banana once in a while (bananas do not digest for me well), maybe lowfat turkey (without preservatives) for lunch on roll or white bread with natural applesauce. Dinner tonight is going to be a turkey leg (shared with hubby), canned spinach and little stuffing (I love it). I do not eat raw anything. When out to dinner I eat small steak or white fish broiled, baked potato and roll or bread - rarely eat veggies. I make a lowfat pizza and spaghetti once in a while.
Just to show you what works for me. Keep a journal and you will see what you can or can't eat and how it affects you. When I wake up in the morning with nausea I have probably eaten something really full of fat or preservatives. (and maybe too much sugar) I only eat Stevia for sweeneter and sugar.