The only way you will have a chance of getting it approved at this point is to do another six month diet where your bmi remains above 35 and send them the new diet along with a weight from 2006 and 2007 showing your bmi above 35 and also your records showing your diabetes and treatment.
It is best to send the appeal letter to the appeals department on the cigna letter and send it with a statement saying what they denied you for and how you are proving they are incorrect... such as ... I am writing to appeal the decision for lap band surgery... in your denial you stated that I did not meet the following guidelines..... I am enclosing records showing my bmi of ... for the past 24 months along with my medically supervised diet and any thing else they said you needed.
Just remember that with Cigna your nutritional, psychological, recommendation letter, and surgeon evaluation are only good for 12 months so if any of these are older than that when you get ready to resubmit you will need to do them over again.
Good Luck