H Cherylj, you wont, you can never get a sick cat to eat, its up to him when he wonts to eat, you will just have to weight for him to nudge you, dont put any fresh food down for now just dry food, and keep a eye on it to see if any goes, but when he does get him on fresh tinned food not dry, at 16 I would just keep him on fresh food.
Good Luck
If he's drinking water he should be alright. He will eat when he is ready..he most certainly won't starve himself. Although, I would advise you to take him back to the vet to have a doctor look at him and to make sure there isn't something more going on with him. Best of luck!
They like humans, when you not feeling well, you don't eat much...If he is drinking loads of water - I am sure he will be fine until he gets his appetite back... however if he hasn't eaten for 4 days - maybe he needs to go back to the vet.... good luck