Has any stress happened in his life could he be anxious about anything, how is work going? Does he eat at work, how is his drinking does he get plenty of Fluids, I wonder if you let him go his own way if he will realise he has to eat, and that like a kid he is getting attention.from not eating! I know it sounds simplistic but I have found sometimes answers are under our noses, Please let us know how it goes it is intrigueing.