Im going to the dr. friday to get info on LapBand surgery..They told me on the phone that i have to go on?

their diet for 6 months first. im wondering if i lose weight on this diet, then they wont let me have the surgery...OR are they trying to see if i can stick to a regimen cuz after surgery there are strict eating guidelines.. i really want the surgery, so should i "fake" the diet???