Approval problems

This is a question for a friend who saw my success and began his own journey through weight loss surgery. Has anyone else had problems being approved by the insurance company (Aetna)? He was required to have all the tests done and to attend 6 months of supervised diet with a nutritionist, he's done all but with a big problem, he gained weight during the six months. I had been telling him it might be best to begin getting his head into it, I was cutting back on fats and carbs three months before my surgery, so I was in full swing by the time I was recovering. He's morbidly obese and has co-morbidities, so an excellent candidate except getting control of his eating. His PCP has spoken to the insurance company, and they still rejected him, now he's persuing a formal complaint. Has anyone had any luck fighting them? I don't know what else to offer in advice, hope someone else can.