It depends how much you have to lose, if you stick to plan 100%, if you follow the rules and if you are determined!
The losses can be anything from half a pound to 6lb a week in my group but, as ANY diet club will tell you, the best and healthiest loss is 1-2lb a week.
SW is a fabulous plan which works for me. Go along to a group, there's no obligation - someone came to our group, listened to the talk, sat through group and then decided if she wanted to join. She did and had a fabulous 5lb loss this week!