Does it matter what type of pre op diet you are on or just that you lose weight?

In my opinion, you need to follow your doctor's instructions to the letter or close to it. Not every doctor requires one, some are much more strict than others, but hopefully you picked a doctor that you trust, so this is an area that I don't believe you have a lot of leeway.

My doc gave me a 2 week pre op of full liquids. The first couple of days were hard. It did get easier. He told me if I didn't lose weight on this pre op he would postpone the surgery. Also if I gained weight he would postpone it. Definately follow your doc's instructions.