Living in mass with medicare

Does any live in Mass. and have Medicare. I was wondering what the requirements were. I called the insurance company and they didn't seem to know anything. I think I have a 6 month medically supervised diet program to complete. Has anyone done that and what is it that you had to do for that. Has anyone been really close to the 40 BMI with no comorbidities since all mine are just borderline. My BMI is now a 41.5 but worried if I loose to much then I won't qualify for the surgery. If I qualify then I will be going to Burlington Mass. but doing my pre surgery appointments in the Danvers/Beverly hospital. Of anyone out there has used them for bariatric surgery or is going to use them I would love to hear from you. My niece went through them and did fine.