Also wanted to add that I know everyone is different and loses in a different way. Typically larger folks like myself tend to lose at a more rapid pace in the beginning.
So to give you an idea of how it has gone for me: I lost 38lbs on a 6 month mandatory preop diet. It was in the middle of the holiday season 2011 so I lost a month and half of losing because I chose to enjoy the holidays. I did not go crazy eating and I managed to maintain. So I pretty much lost nothing mid way through November and all the way to Jan 1. I got back at it and started slowly losing and the day I was approved for Surgery 3/30/12 I was down 38lbs. I had surgery on 4/16 and as of yesterday I have lost an additional 84 pounds. I did that without hardly any exercise. I got a little more active but not like going to a gym or anything. I know the weight would drop faster if I got more active and had an actual work out routine. I guess I am just not there yet.
Sorry, I got long winded but my point is it does work. Follow Doctors guidelines and get in the zone, Get the proper band adjustments and when your appetite disappears you can lose the weight. It doesn't matter if you're 600 or 400 or less. Start the process and get motivated. Find support meetings to pump you up and boost your drive and ambition then things will start to happen.
Remember though where ever your starting point is....you didn't get there overnight and the weight will not come off overnight.
I'll get off my soapbox now!!