One thing you have to pay attention to while aiming for a 12+ hour gap is that you don't accidentally consume calories in drinks, especially from sugar... so no milk, honey, or sugar in your tea or coffee. A little sugar calories will prevent the switch flip, leaving you in a starvation state where you feel awful and eat your own muscles.
Fyi, I've heard health professionals, like Rhonda Patrick mentioned here, say that coffee and tea will still cause your digestive system to secrete enzymes that can undo IF effects, that you should only drink water during the no-eat window. I've given up my morning caffeine to do it.
I’d say that getting adapted to black coffee (I previously took it “light and sweet”) was the hardest part of starting IF for me. Took about 2 weeks, but now I’m enjoying it.
