First of all, why were you water fasting in the first place? There really is no place doing this in a healthy way of life, except for short periods before surgery etc. etc. Most research says water fasting is dangerous, and at the least not good because it causes muscle loss, and even brain damamge in some people.

Coming off of water fasting in any fashion, including atkins will almost certainly result in gaining weight. If you add foods to quickly it can even result in a person needing immediate medical attention.