cat needs to gain weight

my cat carrot has a sensitive stomach the only food i have found that won't make her sick  is Purina one smart blend sensitive systems. she is very thin, and is always sitting at the heat register and sleeping under my blankets at night. how do i get her to gain enough  weight to keep herself warm quickly  without making her sick?

Hi and welcome!

A little more information would be helpful to give you the best help possible How are you feeding her? Do you free-feed her or do you feed her 'meals' during the day? How much would you say she eats in a day?

Have you spoken to your vet about the problem? Does he or she agree that your cat has to gain weight?

Hopefully others will be along with suggestions soon!

Maybe she needs deworming and that is why she gets queezy when she eats. Feed her grain free canned and not dry food, see if that helps.