At least in the case of ramadan fasting, the difference is that you eat (and drink) nothing at all from waking up until night. This way the digestion system never gets started, the stomach kind of just shrivels up and you never actually feel much hunger.
Incidentally, Islamic practice is to fast two days of the week too (outside of the month of ramadan).
Incidentally, Islamic practice is to fast two days of the week too (outside of the month of ramadan).