I have United, they are a pain. Keep working on the insurance approval and follow exactly what they want. I started at 370, did my 6 months in which I was definitely expected to lose (modified South Beach Diet for 4 months then I ate like it was my last meal! I stayed at about 310 for last couple months.) My surgery was Dec. 10 lost about 37 since then, My goal is to be under my college weight of 227. I am at 269 this morning when I stepped on my home scale before getting dressed.
United wants you to prove to them that you are serious about losing weight and that you will keep at it. They require you to go to Diet Dr. or equivalent every month. It was a great way to get used to bariatric foods. I found I could eat plain nonfat greek yogurt with Peanut Butter powder, fresh fruit, or even diet maple syrup mixed in. I learned how to eat 60 grams Protein a day and to follow a tight diet while walking a bunch. I was worried about losing too much, but that is unlikely. My Dr. told me that if I started losing too much she'd put me on a Golden Corral diet for awhile.
I also think United wants people to re-consider if they are doing really well on their own diets and NOT get WLS.