Hi Skipper...
Having never been to OA, I can't say for sure, but I know they are NOT about any "diet" in particular. You will have to come up with something that works for you, preferably in a healthy manner. Instead of looking at it as a diet, which is something that you go on and then off, presumably when you are done, why not find an eating plan that you can follow for the rest of your life? Weight Watchers is a good example, but certainly not the only one.
Try checking out the website,
www.overeatersanonymous.com for more info about that.
Good luck to you!