Off topic, but what causes a dog to over eat? Some dogs eat until they are full, others eat until they become like a hairy ball that has to go outside to shit every half hour, given a moment's lack of supervision with a food source nearby.
Late and gay as many others have replied already, but you did specifically ask me, so! In my opinion, the main factor is just a dog's natural personality/genetics. In my experience, you can (and usually should) free-feed a dog without issues - animals naturally stop eating when they're full and don't over eat as long as they feel their food source is secure. A dog can start over eating for multiple reasons - food scarcity being the main one, poor food quality, food being "stolen" or taken away, etc. Most of the time and without complicating factors, unless it's just because that particular dog is neurotic and dumb, the issue is solved by giving the dog free access to a high quality food. They'll scarf it all down at first, but after a few days or a week when they realize the food isn't disappearing on them, they'll calm down. If they eat too quickly, you can always get them one of those puzzle bowls meant to slow them down, but I only reccommend that if there's risk of choking otherwise. Unless the dog has a serious mental issue, it won't gorge itself to death, it just might gain a little weight that it needs to run off.
Dealt with a stray pick up not too long ago who'd been on the street his entire puppyhood into young adulthood. Real bad issues with raiding absolutely any and all food, snuffling in the garbage even when he just ate, etc. He was pretty well traumatized, emaciated and near death when he was found. His food had to be limited at first to not cause re-feeding, but once he went home after a month he was free-fed a good quality puppy food. He settled down in less than a week, even after going through all that, even stopped the garbage can raids. He'll hoover up anything you drop on the floor and he begs if you're eating, apparently, but you can leave food on a surface he can reach and he won't go for it unless you tell him he can have it, even when you're not in the room. No resource guarding either.
On the other hand, a friend of mine once had a lab who
would eat anything and everything in sight, to the point that she nearly died of it on multiple occasions. She would eat an entire bag of dog food in a single sitting, then be so full that she literally couldn't move. She ate animals alive all the time. She'd steal food from the fridge, food if you weren't looking. People food, dog food, cat food, vaguely food items that most people wouldn't even think of as food, bait/poison items. She apparently loved to steal beers in particular and would bite the caps off to drink them. She was absolutely fucking insane, and somehow lived to be almost 20 despite all this. Her worst case was when she ate
a whole pork hide that was curing in their barn. Like, she didn't even really tear it apart that much. Being country folk who didn't believe in seeing a vet when a bullet is just a couple cents, their solution was to wait until she started pooping it out, then
tie the fucking end of it to their tractor, and let her "work it out" by herself. She fucking survived this. She also had a habit of laying too close to bonfires because she loved the heat, and on multiple occasions would actually lay down on the fire itself and then run yiping away when she caught fire and had to be put out. Brain smoother than a fucking river rock, that one.
All this to say - really depends on the dog. But as someone else in the thread pointed out, retrievers tend to have pica and will over-eat more readily than most.