Galina was on prescription food (it was Science Diet something for food allergies) and I used to just just one thing of food for both cats, but after that, I had to start feeding them at scheduled times and watch them while they ate to make sure they were eating their food and not the other's.
From my experience, Science Diet does a good job. After the precription food ran out, I bought the store brand and it did just as well.
I don't know of a more natural alternative.
I was fairly strict about Galina's prescription food and about her eating it, because it was just too expensive to have to buy two bags for her AND Gerona.
But, all in all, I find the Science Diet prescription to be fairly good. I've even used A/D to help Galina gain weight when she was a baby and wouldn't gain weight with ANYTHING else we gave her.