Two cats and my cat keeps eating the others food?



My roommate just got a kitten but he buys her the cheapie whiskers cat food. I like to feed my cat the premium Natural Balance cat food because its ingredients are better but no matter what flavor I buy him, he always wants to eat the cheaper stuff and they just keep switching bowls. Even if I try to separate them, the kitten will just eat all her food and then eat all his food too! What should I do??