Fasting and timing one's eating are two sides of the same coin. So even if you're on a kind of standard three meal a day with a couple of snacks in between diet or nutrition regimen, you are fasting whenever you're asleep, or you're not ingesting any calories. So unless you're hooked up to an IV of glucose you are fasting while you're sleeping. There are several different kinds of fasting that can relate to epinephrine and cortisol.