I feel like after a meal, especially OMADs which tend to be a little heavier, I need to wait about 30 minutes before I consider it a fast lol. Does it matter?
The minute you swallow your last calorie, you have officially started your fast. No need to wait an extra half hour. Your body has already started digestion and according to the IF world your fast has started.
I personally don’t time my fasts because I do OMAD. My one meal a day is dinner, and sometimes dinner is at 6, sometimes 7, or as late as 8:30 on busy days.
I would say that fasting starts after you had the last bite or sip of something with calories.