Wild cats teach their kittens what’s safe to eat, after all some animals they might think are food would actually harm or kill them. This built in mechanism to keep them safe is the same one that makes it hard to switch cat’s diets if they aren’t used to eating a variety of foods.
No matter what you are feeding, try offering raw food, making sure that you warm it to room temperature. If you are not successful in getting him to try it, put a little on your finger. He may take it directly from you this way. Cats that are eating canned food will often eat raw food mixed with it. If you are feeding kibble, try offering canned food first, and then when he eats it added a little raw to it.
Remember that your cat will pick up your energy, and if you think you will be unsuccessful making the switch you probably will be.
Don’t let your cat’s age deter you from switching his diet. He will benefit at any age from an improved diet. If your cat has any health problems, you will want to consult a raw feeding vet first.