Well, my doctor doest require it and he is against it because he says it is too long for a person to stay on a low calorie diet because after the surgery he requires 3 weeks on full liquids. He says that if his patients did a pre op and a post op diet, they would gain when they start eating, and i agree. he is the surgeon who does the most lap band surgery in canada.
However, he requires us to loose 10% of our exces weight, i ended up loosing 50 pounds. I was nervous, and i asked him before surery if i should go on liquids, he said that my weight loss would garanty a small liver.
HOWEVER! The week before the surgery, i had a bit of junk food, i didnt gain, and when he operated, he was very surprise to see that my liver was still fatty. He said it is genetics, and it is true, in my familly we tend to have fatty livers.
So if you do not loose much weight, try to diet before, like the last 2 weeks. Dont go on liquids, i am starting my second week om liquids ad it is absolutely horrible!! Id get on a strict diet just to be 100% certain he can operate on you, and im against diets:) .
Good luck