Once I really locked in on a baseline of 16/8 it became completely automatic. My fasting window was originally 8pm through 12pm the next day. At this point I can't even imagine eating before noon. So that frees me up to really play with my window and extend my fasts. Most days I'm not hungry at noon, so I don't eat. It's easy from there to push the window to 4pm and be at 20 hours fasted. Then on some days I'll just go 23-24 hours. Once or twice a month, I'm still not hungry, so I will completely skip that day and break my fast at noon on the next day - 40 hours fasted.

The longer fasts have completely retrained me to separate physical from mental hunger. Mental "hunger" comes in waves - for example if you typically eat every day at 8am, you will be mentally "hungry" at 8am every day because that's when the brain is used to eating. But if you push past that time, by around 9 or 9:30 you aren't "hungry" anymore, because you were never actually physically hungry. Your body can go much longer than that. I will say that the physical hunger can be difficult to predict, especially when you are active and working out on a regular basis. There are some days that I feel REALLY hungry at noon, and others where I go the entire day without feeling that physical hunger.