The primary role of food is to fuel the body, like gas fuels a car. Just as it is not necessary to overfill a car’s gas tank, eating more food than you need is also unhelpful. Your metabolism can adjust to an occasional overeating experience. But, if the overeating occurs daily or even weekly, your metabolism cannot burn off the extra calories.

Comfortable Fullness: The Key to Avoiding Excess Calories.
In order to stop eating at the point of satisfaction or comfortable fullness, recognize the feeling of physical satisfaction and learn to stop eating at that point. It doesn't matter how much is still on your plate. Save it for another meal!

Fullness Signals. During your meals and snacks, you should pay attention to how full you are getting. Below are some common fullness signals. Be sure to add your own, too!

What does comfortable fullness feel like?
It's a feeling of satisfaction or relief, like: “Ah, I’m not hungry any more.”
A feeling peacefulness.
No more stomach pangs or twinges.
Feeling like you don’t need any more food.
Food starts to taste less good.
At the edge of pressure on the stomach.