The stomach is the size of two palms-if you cup your palms that would be the size of your stomach. If the quantum of food you are eating does not / will not fit within the cupped palms of your hand, then you have crossed the food threshold level. As you pick the food with your fork/knife or spoon , look at it – know what you are eating, savor every bit of food. And soon you will know when to stop eating.