Diet really depends on how ill you are. Three years ago I was in the mild to moderate range, and was still a bit active. I was able to do the HCG protocol with 500 calories a day, and I felt AMAZING! I lost 60 pounds in one year, and as I started adding foods back into my diet I was able to find some triggers that I wasn't aware of, like walnuts and bakery yeast.
Now that I'm in the moderate to severe range, I know I could never survive a diet plan like that, so I'm really glad I did it when I was more functional. (I did try doing the HCG injections without restricting calories, just to see if it would help control my ME symptoms, but I never felt any effects from it. I'm not sure where that initial high came from, unless it was just my body detoxing from everything.)
Whatever meal plan you choose, make sure you do it with the advice of your doctor or naturapath, and be sure to take lots of both pre- and pro-biotics!
BTW, still holding steady at 130lbs, with no regaining problems. I eat a pretty "normal" way now, just with fewer carbs than before.