I had a friend in college whose dog would absolutely refuse to eat dog food. It would do so while its stomach was growling right in front of us. I was told that the dog would totally ignore the food all day long and would normally polish it off right before bed on a daily basis. It wasn't temporary, this dog just really didn't like dog food. The owner wasn't heartless, he tried a lot of different brands but there was just something about the stuff that ol doge wasn't into. I don't think this ever changed either.
I have a friend here in town who has this massive American Pit that looks like he could devour an entire bag of Pedigree in 4 gulps. It is quite humorous to see how fickle he is about what he will eat. His owner put the food out at the same time each day and tried using various methods to get it to eat that he read about on the internet such as taking the food away after a certain amount of time. The dog would eventually eat but it just seemed like a rather joyless process for him. He also didn't like "Sweeties" (the name his owner has for treats) and would pop them in his mouth, and then drop them on the ground at which point one of his huskies would come by and gobble it up.
It's amazing to me that this animal maintains his massive size given how completely turned off by food it tends to be.