It is true. My policy has always been that I will eat fairly badly, but make up for it with more exercise. And I have to admit thyat I moved out of home for 12 months and lived on the beach, during that time I ran every day and ate fairly badly, but never had one IBS incident (remarkable!).
The next year I moved back home, and I was doing the gym scene, but only about 2-3 times a week, and i was back to having IBS attacks again. And as anyone here probably knows, IBS is the worst for keeping up regular exercise, because it knocks you out for a few days, and you have to keep recovering.
Id need to test my hypothesis again, but I think the regularity and intencity of the running really helped keep everything moving, more-so than walking or static weight exercises.
In my case, im 'compromising', I know what my body doesnt like, and I stay away from it, but at this stage I am not willing to give all spicy/rich foods away, because I love them too much. Of course your body will tell you if it strongly disagrees. For instance recently (from nowhere) I started breaking out in hives, all over me. My bodies way of saying, look... youre giving me something I dont like it.. stop it, or youre gonna cop it real good. I ignored it for a while, but it got worse.... eventually the suffering reaches equilibrium with your motivation to do something about it. Now Ive make an effort to find out what on earth the problem is, whether its food/drink or even a soap or detergent. Id rather make this change, then endure the suffering.