Atkins says average weight loss is 10% of what you need to lose during induction, and 5% each month after that. For instance if you had to lose 100 lbs, the avg. weight loss would be something like this:
induction: 10lbs
month 1: 4.5 lbs
month 2: 4.3 lbs
month 3: 4.0 lbs
and so on