I wouldn't touch Iams, Nutro or Eukanuba.. those have junk in them and will contribute to gaining weight.
I would recommend Canidae because I used to feed that to Oreo & Ginger, but I feed them Innova now, but I think after the bag of innova i'm going to put them on Artemis Osopure.
These are pretty good/high quality foods, we do want nothing but the best right?