Dr. Atkins writes that a small percentage of people will not lose on induction. He has a lot of information for these people in Dr. Atkins' New Diet Revolution and suggests ways of diagnosing various reasons -- yeast, low thyroid, etc. I would think that much of this probably applies to people who gain weight on Atkins. I don't want to summarize it all here because I will probably get something wrong. You might want to take a look at the book.

I am sorry you are having this problem.