Comment by hinkley
There’s some documentation out there suggesting the original Labrador retrievers had food obsession as a trait in common with bidability, which is why more than half of them end up chonky. Not all have the gene but odds are high.
There’s a guy who trawls dog rescues looking for retrievers who are toy obsessed and then trains them to hunt truffles. He reasons you can’t reward them with food for finding even tastier food, so you have to train them with ball time as a reward/distraction when they find a trove.
Labs in general are notorious for having insane food drive to the point where when you run into one that does not, they're certainly an exception. All dogs in general have food drive, as it is a necessity to live, but they're given basically unlimited access to it which diminishes it's value in their psyche.
Once you pull that prey drive out of a working dog and associate it with something such as a ball, there's no greater satisfaction this planet than doing the thing for that animal. It usually works better as a reward for what we're doing, is more instant, but also it can be deadly for a dog to eat food when they're at working-level activity.