With the intermittent fasting I noticed that I am usually hungry upon waking up, but it quickly goes away if I am of a sufficient weight and/or overfed the day before. It is the mounting hunger that I aim to satisfy, in other words, the one that doesn't go away after 30 min-1 hour and that becomes destructing.
I understand that i did not discussed the hormones, because frankly I can't wrap my head around it though I tried, but fwiw, my ability to fast is entirely dependent on my weight and on the previous day's calories. Sometimes I just get full. Love that feeling. I IFd 5 days a week at the weight of about 123-125 lbs for months. Also, going out to train instead of sitting at the desk at work makes hunger less noticeable. At some point the body gives up on the 'feed me' signal and I can push the meal till 10 am-lunch instead of 6-8 am (I get up at 3:30-4 am).
My biggest no-no to fasting is when I start waking up at 2 am hungry. That's when fasting and caloric deficit is off the list.