Modified Diet

Hi, I am in the first stages of my journey, currently at 275. I had my first Dr visit and NUT visit. We are going for the 90 day plan for my insurance. My NUT has put me on a modified pre-op diet as of now. Funny thing, she did it before she realized that I was doing the 90 day as opposed to 6 months. Was she going to have me do it for that long? Is that normal? I get three low fat, low carb protein drinks, a small meal, and a snack per day. I know they want to shrink the liver, but this seems likes it's going to be really long time.