My vet told me (and you may remember Filou is a kidney patient too) that of course they need diet food, but it is important that they don't loose weight.

Filou did not eat the Hill's k/d (although I know some kitties love it) but he eats the Royal Canin Renal food. He even liked it better than his brother's normal food and I'm glad about that because I still can feed them together.