Fasting

Off unless you turn it on in Settings, because it only means anything if you log at your eating times.

On, Today shows a live count from your last log once four hours have passed, and a quiet "fasted 16h" line after you eat. The four hour floor stops a normal gap between meals from being called a fast.

Tap the pin to put the fast on your lock screen as a Live Activity. It ends itself the moment you log food.

It is a clock. It has no target hour and it never grades you.