I'm exceptionally skeptical of any shake or product that says that it does ANYTHING. If 100 doctors that I KNOW are doctors recommend it, then maybe, but I have to see degrees. Even then, I would wonder.
Nature gave us everything we need to keep our bodies balanced and healthy. If you're not going about it with good nutrition and exercise, you'll likely only succeed for a very short time, if at all.
I think you should ask your OWN doctor about it. Not just go off of what you've heard on their website. They pay people to write that stuff. The only things from Beach Body I would/have purchased are their exercise programs. Many of them are pretty hard core.
Do you happen to post about IBS on IBS forums? Because there are hundreds of forums out there for your condition with people who are much more knowledgeable (Even real doctors post on them). You don't get points for posting there, but you might get sound advice.