His name is Monster (earned when a mischievous kitten) and he is now 13 years old. I'm concerned because he has become skin and bones although there is always food in front of him. It may be time to see the vet, but I'm looking for any knowledge or experience readers may have that may explain this or suggest what may help him. He throws up fairly regularly too, but with 3 cats in the house I don't always know which cat it may have been.