I always think about the 'will power and make an effort' when my friend with her labrador visits. I have setters. They are not food driven. Sure, they like treats. But when I feed them in the morning, they may eat food, or may leave half of it, whatever. They are effortlessly slim.
But when the labrador comes, I have to remember to lock everything edible away, because the dog will find and inhale it all. My friend has to carefully restrict and monitor the dog's food intake, otherwise the dog will quickly become overweight.
I won't tell her that she should just be more like me, see how easy it is to have slim dogs?