I have heard that when eating one should allocate a third of his stomach for food, another third for his drink, and the remaining one third should remain empty. How can one know how much is one third of his stomach's capacity?
We are been advised to eat less and leave the food when you are still feel wanting to eat more. That will then leave space for drinks and breathing. It comes from your personal experience which makes you able to estimate the one third for food and the other third for drinks and the last third for breathing properly with out feeling full or heavy.
Wassalam..