awesomesprout

I don't think you should be worried unless kitty is clearly LOSING weight or isn't healthy. If he's lethargic or shrinking, yeah. Otherwise he might just be comfortable at a skinnier size. There is genetic diversity, and some members of any species are just skinnier than others. If you're worried, take him in, but really if he's been happy as a clam at that size for two years, probably nothing is wrong.