The Atkins Diet actually consists of four diets instead of one. The first two weeks you are asking about is called
"The Induction Phase"
The Induction Phase lasts for a minimum of two weeks and a maximum of one year.
Your answer...
You can generally expect to lose 10% of your excess weight during the first 14 days of induction.
That would be about 8.2 kilos
The goal of the induction of the atkins diet is to adjust your unbalanced metabolism by restricting the daily intake of carbohydrate to 20 grams or less.
When you take into account that one slice of bread contains around 15 grams of carbohydrate, the induction phase is pretty dificult to do.
I read on the web that you should follow Induction until you loose about half of the weight you need to lose.
After that you can jump to phase two:
Phase 2 --> Atkins Ongoing Weight Loss