If you fall off one you might still be on the other one. Like today for instance I was on south beach in the AM and just a low cal in the afternoon. I am sure that cancels out my south beach and makes it gone but I don’t feel like a total failure because I still stayed at my calorie budget. Just in a bad unhealthy way- I had a tough afternoon with car breaking and needing gas and getting soda and beig hungry and late that I just had a bag of potato chips at the gas station. I said it. Worse than that… I ate it. Bad. BUT I was still ok once I counted my calories today so I think I win today. On a technicality.