In my opinion you should draft your letter prior to your visit and ask your pcp to place it on their letterhead. Of course tell them you are doing this for bariatric clearance/surgery..I had no problems. This is what I did and it benefitted me greatly. Here is a link to a sample...I included diets such as atkins, sugar free, low caloric intake, raw foods, etc and was approved no problem
http://www.drwizman.com/PDFs/med_letter.pdf