especially if he is overweight. He has clearly had access to good quantities of food in more recent times. Mind you, some cats never get over a period of starvation rations. But if he is scoffing food down and is already overweight and you do not know his history, then off to the vet you go, I am afraid. Mean time, figure out what he Should be eating in the course of a day and ration it out in small, frequent meals so he does not accidentally get over fed cos you lose track.