MEDICARE-MEDICALLY SUPERVISED DIET?

Hi everyone! I have been AWOL the last few weeks. I have been very busy fighting with my insurance company Independance Blue Cross Blue Shield to get a revision from a vertical banded gsatroplasty to a duodenal switch. I was denied initally right off the bat. I filed an appeal and that was denied. It looks like the insurance policy is iron clad when it comes to revisions for any reason as an exclusion. 
So...I am going to try with medicare part A and Part B. I have everything in place except a medically supervised diet. Does anyone know how many months MEDICARE requires of a medically supervised diet? Any info would be appreciated. Thanks.
*I would like to take this time to all who helped with with kinds words, encouragement and information during the process. It has been very hard on me.

I was approved by medicare and did not have to go on any special diet at all.

I am medicare part a and b...in Texas ..it was 6 mos in my case and I just completed my 6 mos on friday...waiting for a date..  there are 10 people waiting for dr..only one dr in that office is taking medicare

I am so sorry, I am not revised.  I am waiting for lap band or RNY...NOT REVISED