I actually can tolerate fatty foods, so long as I don't vary the amount of fats that I eat very much. I have found a consistent diet is very beneficial. At the very least it allows me to take the same amount of medicine every day. When I went off my diet last week while on vacation, I ended up messed up. And really I didn't get messed until the end of the week when I got away from my sandwhich lunches and started eating heavier meals at various food places. I also ate eggs every morning later in the week and while I can tolerate them on the weekends, I can't really seem to do eggs every single morning. Or maybe it was just the sausage and/or spaghetti sauce I had on them.
Starrr, you mention needing fats, especially good ones. Me, when I cut almost all the fat out of my diet, I got severely constipated, so that might not be something that IBS-C people try to do. On the other hand, if it helps you, go for it. I totally agree with you, Anna; if everything's going to make me sick, then, by Jove, I'll just go ahead and eat whatever I want.
I generally avoid fried foods, especially fast food which is about the greasiest thing known to man. Really it's the grease that does me in, not the act of frying. Because greasy meats that aren't fried will bother me (as I relearned last week from eating too many sausages and other things--I'm still recovering from it too). My grandmother's fried chicken, on the other hand, does not bother me because she uses little oil, does it in a skillet, and always pats it dry before serving it. Last time I tried it, Chick-Fil-A's fried stuff didn't bother me either because they deep fry in peanut oil, not vegetable oil, which is a different (and good) fat. I don't seem to have a problem with nuts, but then I don't eat them in large amounts or real frequently. Um, except when I get the honey roasted peanuts, then I can eat quite a few at once.