I would call the vet to ask him about changing your cats food to a light formula. Some cats just have slower metabolisms than others. My cat Pepper is about 17lbs and he's about 3lbs overweight but he's a lazier cat than my other two. If you have not been to the vet in a while then maybe you should make an appointment for a physical and then you can discuss his weight. Good luck. I also look forward to seeing his pics.