There are a lot of threads in this forum (and, I suspect, in the Atkins-related forum) about this issue. Try doing a search to find them.
I will say, however, that it takes time to read the book, prepare your house and mind, and get ready before starting a new plan, if you really want it to work. So I wouldn't plan on starting either tomorrow. Check out the Prepare Yourself to Start South Beach
thread (stickied at the top of this page) for lots of hints on how to successful start this plan, if that's what you decide to do.