Pollyanne,
Everyone is different... I am actually very surprised that you lost 7 pounds in your first week of induction, because you have so little to lose. Usually, the rule of thumb is about 10% in the first two weeks, and you lost 35% in one week.
Have you read the book? Are you using Atkins to lose your 20lbs or are you planning to eat this way forever? If you are planning to make this your woe forever, make sure that you read the book, because you will need to move into premaintenance shortly, since you are so close to goal.
Best of luck to you!

Jenn