water-fasting is a much more efficient process of detoxification and healing than a juice fast, although this does have very distinct health benefits, and as long as the juices are many and varied, to provide you with as near a complete nutrition as possible.
If you are worried about the undertaking of a water-only-fast then probably best not to, but excessive weight gain post fast is usually down to the wrong type of foods. If you adhere to what is known as a Nutritarian eating plan, which is essentially one which is low-calorie but nutrient-dense, you will not regain any excess weight, whilst providing as near to an optimal nutritional status as possible, given the depleted nutrient content of many natural foods because of soil nutrient-depletion................. http://www.drfuhrman.com/library/are-you-a-nutritarian.aspx