I don't know why but I was given only a 10 day pre-op diet with 1000 calorie limit as long as there was really low or zero carbs. I have surgery on Monday and at my pre-op surgery appointment with the surgeon the nurse said I could have a salad and half a sandwich the day before. It seems many people are required to do the 10-day pre-op diet but I've been hearing a lot that the pre-op can be different for varying BMIs. My BMI is 40. I just hope I'm not doing anything wrong.