I'm an overeater, here is how I quit:
Give yourself a serving size of your meal and eat slowly, when you've finished, go and brush your teeth. Not only does the toothpaste make food taste terrible, but it also lets your mouth know you're done eating for awhile! It has helped me!
You can do this anywhere, even if you are out to dinner with friends, just pack a travel toothbrush/paste in your bag. Extra tip: if you drink water right after brushing your teeth or eating a mint, the fresh breath taste lasts longer!