I was not required to follow a liquid diet before surgery. My surgeon's office only requires no carbs, no sugars, and 3-4 ounces of meat per day for 10 days preceding the surgery. They say it's to shrink the liver so it's not in the way for surgery and gets your body in the right "frame of mind" for recovery. I lost like 4 pounds in those 10 days. Now. Here's the thing for me (personally). I was one of the "close" ones, as in, I "just" qualified for the surgery. Had I lost much more than that, I would have become ineligible. So, I did the no carbs, no sugar and all the meat that I wanted. This was under the advice of the surgical/registered nurse. To which she explained the sugars/carbs affect the liver the fat of the meat would not (in the time-period given).
Good luck and keep us posted!