Can you sue a health insurance company for denying medical coverage?

My doctor has referred me to have the gastric by-p surgery. I've spent the last 4 months and countless money (of my own) getting all the things the done the insurance company has asked for. This includes psych evaluation, sleep study, nutrition counseling, physicals and doentation to include I have tried at least 2 non-surgical weight loss programs for over a year with no long term success. Finally after submitting everything, they denied me for "no recent active participation in a non-surgical weight reduction program". My last weight loss attempt was a year ago. I am about to lose my job because I cannot literally stand up on my feet anymore. This is something I have to get, not something I just want. It would seem if both my primary physician and the specialist both agree this is medically necessary, then the insurance companies couldn't deny someone their health.