Is there a must to loose weight during the pre op liquid diet, in order to have the surgery.

This is something that you need to ask your surgical team, as there are no standards when it comes to pre-op dieting - they vary from nothing at all to several weeks of liquids and everything in between. It would really come down to what the intent of the diet is (and after all the years of reading these forums, I still haven't figured out what the liquid diets do.)

Is there a must to loose weight during the pre op liquid diet, in order to have the surgery.

It really depends on your situation and your surgeon's requirements.

My pre-op diet's sole goal was to shrink my liver. Weight loss was not a requirement (although it may have been a by-product -- I don't know since I didn't weigh during that time).