I have four cats all of which are healthy and active. I have three females who have been spayed, and one male who has not been neutered. One of the females is overweight, two are about average, and the male is very thin. They are treated for fleas and dewormed if I notice any signs of worms, either on their fur or in the cat box. They eat out of a pan that is filled and then emptied by them twice daily, once in the morning and once at night if the pan is empty. I would have a hard time separating them to feed because they have full run of my apartment at all times. Should I be worried that the thinner cat is not getting enough food? Is there a sneaky way that I could give him more food, or because he is active, if thin, should I just let him be?