@Purple Frog - Yeah, it was not fun. Also, the first go around, I was doing something legitimate - eating real food - low calorie. The second go round, I did something really unhealthy, which was to repeat a liquid diet designed only for short term use. My DS surgeon actually made me quit the liquid diet for a month before surgery as he was concerned it was going to have detrimental effects, specifically impact to the good bacteria in my gut.
That said, I did what I had to do to get the DS approved. Took me 18 months of fighting and two unnecessary pre-op "diets", but that was well worth it in the end...
Anyway, I only mention it as warning, so that others don't have to suffer twice plus have everything delayed. If there is a pre-op diet requirement that you are trying to meet, make sure to read the fine print and learn exactly what will qualify as "medically-supervised diet" in the view of the insurer, so those efforts aren't wasted. It was a HUGE disappointment to me to find out that I had to do it a second time. My mandatory "medically-supervised diets" were also 6 months long, which is torture.
Specifically, the questions I would ask the insurer are: How frequently must I visit the doctor? Can I phone in my weight to the doctor's office or do I need to be weighed there? Is there a mandatory weight loss amount to demonstrate compliance with the diet? Would nutrisystem/Jenny Craig/Optifast/whatever count? Does the doctor need to provide counseling and demonstrate it in his/her notes? What will I need to provide as proof of compliance.
I know others have been successful at fighting the pre-op diet requirement with help from volunteer advocates / vets who are here on this board, but at the time I was going it alone and I just accepted it as a necessary evil. Hopefully those folks will be able to assist you!