Canidae dog food..........................…

Ok well here's the thing.. We started on Purina Little Bites, then to Iams Proactive Health, back to Purina little Bites, and now on Overweight&seniors Canidae. I want an all Natural dog food. My mom wants to switch back because the Canidae makes them have a lot of gas. I want to stay with an all natural dog food but not Canidae. 1 out of 2 of my dogs are overweight and they are pugs. I have talked to the vet and he said because of the one dog being overweight means I should put the dogs on a low calorie/diet dog food. Can you recommand a dog food for my pugs??? It would be nice if it was natural.