There are lifestyle factors as well.
My Great Grandfather lived on salt pork,eggs, bacon, and all that stuff, he was skinny as a rail.
But he did physical work and burned it off.
I do the same type of work today, and am fairly careful what I eat and am still getting a gut,
Because nowadays the things he did with lifting and wrenches I do by pushing a button or 2.
Even ditch digging , it used to be done with shovels, now it is done by some guy sitting on a piece of equipment.
Our technology means we can't eat the way people used since we don't need the fuel.