We had two cats. Fed them the exact same way. One got fat and had diabetes, and eventually died because she swallowed something that was not food that got stuck in her intestines. The other cat, he has always maintained a healthy weight. I think it all came down to some kind of feline anxiety though, where she was always seeming anxious, right down to being overprotective of food, and he's incredibly chill and always has been, except when neighborhood cats wander on our property.

We always opted for Fancy Feast pate, had looked them up when the diabetes first showed up, and they're apparently high protein, low carb, and they served us well enough. We mix in some other stuff from time to time for variety, but that's the bulk of it. I'm interested in this Primal though, definitely going to have a look. He is now somewhere in the 13ish range, dunno for certain since he was a street urchin when my wife found him, but we're trying to let him live a long, healthy life, in spite of his urge to die on the streets somewhere.