I have IBS and have been doing Paleo for just 2 weeks. I was eating close to Paleo before this, so it wasn't a big change - I removed my oatmeal, rice milk, brown rice and choc chip cookies. And I've upped my ruminant meats and animal fat.
So far, there's a lot less bloating because I've removed sources of fermentation - I think the oats were the main problem. But I don't feel I'm actually making any progress in terms of getting my gut in any better shape in the big picture. (Although I realize it's early days still.)
But should I be doing some serious no-carb diet for a while to starve off the bad bacteria, then repopulate it with fermented foods? I've seen reference to some people (i.e. Melissa) taking this approach. I'm not sure what fermented foods I'd eat, since the ones I know of are miso (soy = no), sourdough (wheat = no), sauerkraut (gas = no), yoghurt and kefir (dairy = no).
Also, I am underweight right now, so the diet of cutting out all carbs is freaking me out. And I'm not even sure that "bad bacteria" is the problem.
I am taking VSL#3, a high-strength probiotic.