Does medicare require 6 months diet history

I did some research on this and what I found online  is that when medicare changed the rules for gastric bypass approval in 2006 - requiring a center of excellence etc., - that they stated a 6 months diet history was not necessary because most people seeking this surgery have had years of unsuccessful attempts.  Is this correct?  I sort of have this history anyway, xenical and diabetes carb counting thru my primary doctor, but my history doesn't seem as structured as the bariatric surgeon has requested it should be.

I am being told that it is NOT needed anymore.  But it seems like alot of doctors think it still is.

It is supposedly not required as long as you show a past failed diet history