my preop diet was 2 shakes and one very small meal a day...I lost 10 kg in 4 weeks and my liver shrunk to the optimal size for the bypass..its all about learning a new way of living and looking at the way we eat...6 months post surgery and I have lost 50 kg. It seems like punishment at fiest but It is a journey I am glad I embarked on. I gave 40 kg to go to get to my goal. Good luck to you!