overgrooming cat

hi im new here and really would like some advice , my cat male neuterd 7 year old has always overgroomed when stressed vet reasures us that it is just a behavior thing as his mum who my partners mum owns does the same thing, he is also a very thin cat and what i really want to now is ,is ther anything i can give him to help him as in supplements or food to help build him up a bit as were comeing into winter and he dosent have much of awinter coat , all advice greatly recieved.

thanks caz

You could try feeding him kitten food. That might help him gain some weight. Also a good quality food should help with his coat. He may be over-grooming due to allergies to his food as well.

WHat is kitty eating??? Many times it is a allergy to food or enviornment...