Just like an alcoholic has the problem, that he can't just stop after a beer or two.
It's the same mechanism.

Everything you use to cope with emotions can produce that.
Like nicotine itself isn't hard to quit - not much of a physical addiction. But as one used cigarettes as little self rewards and uncomfortable situations, you can't just give up your tool to manage your emotions.

The only way out is to face those emotions and solve the original issue. Else you'll just be hopping through different "helpers"

Edit: maybe to give an even more extreme example:
Cocaine doesn't produce any physical addiction, but because it gives you the feeling of being awake and you suddenly can handle the stress, you'll fell completely lost and alone without it in those situations.
That's why trigger situations are a thing.

With food, just like cigarettes, it's even worse, because you use them for good and bad times.
So the association with feeling good is much harder to break.
As we need food, this addiction is probably even worse, because you can't just stop eating all together and face your emotions. So you're daily tempted with it.
I personally can't relate with overeating/"food addiction", but having spent a month tapering opiate teas (which I used to still be able to work during my burnout), I understand the feeling of constantly looking for an excuse to still do a bit more - just today...
Because this day was especially bad and I desperately need the crutch, or especially nice and I feel like I wanna celebrate it somehow.