It doesn't matter WHAT diet you're using.
As for CKD, of course you're going to lose weight very fast the first week you're on it. However, MOST of the weight you lose during the first week is going to be from glycogen and water, since you're not eating (much) carbohydrates (and 1g of glycogen holds 3g of water in your body), and not that much from fat loss. After the first week on CKD weight loss will slow down, because you will start losing fat (and muscle).
As soon as you stop CKD you're automatically going to gain a good few pounds, and most of that will be food and water weight.
I suggest that you do some research on nutrition, biochemistry, and physiology, so that you better understand the process your body goes through when you go on a diet.
Like I said, don't EVER be concerned with the SCALE WEIGHT; go by BODY COMPOSITION!!!