First, check with the vet for underlying health issues. Is your cat going hungry for a long time before coming inside to eat? If so, try feeding him in shorter intervals. I would change over to feeding wet food at regular times, personally. It took my cat 6-9 months to accept wet food and she's still a dry food junkie when she can get it. We only give her one portion per meal to reduce the likelihood of vomiting, but she gets 3-4 small meals a day.