We have 4 dogs, two are 12 years old and two are 8 months old. We have always fed free choice dog food and have never had over weight dogs.
I don't understand the struggle of over weight dogs at all.
Granny, a puppy that was partially starved will eat ravenously until he gets the proper nutrition. We fed our Cur pup an egg morning and evening until he didn't just gulp it down anymore along with free choice Victor brand puppy food. It actually got to the point that he didn't even want the egg at all. His hair is shiny, slick and as thick as hound hair can be. Last week when the temperature went up to the upper 70's to lower 80's he acted like it was too warm and lay on the dirt in the shade, that tells me he has an excellent coat.
We often feed two brands simultaneously, those being Diamond Naturals and Victor.
Edited to add: we feed breed size and age specific varieties.