The short answer
For the adaptive machinery to keep working: most days of food logged and at least one weigh-in per week. Concretely, the expenditure engine wants around 4 logged days out of every 7, and a weigh-in no older than a week — the same bar your weekly check-in uses before proposing target changes.
What happens below that
Nothing dramatic: the estimate pauses instead of guessing, your targets stay where they were, and everything resumes when the data does. Missing a few days doesn't undo your history.
What more buys you
Consistency converts directly into confidence: fully logged weeks and regular weigh-ins move you to a Refined estimate and keep it there, which makes check-in suggestions as personal as they can be. Daily weigh-ins aren't required — but they make your trend more responsive.
Perfection isn't the bar
A forgotten dinner or an unlogged weekend is normal life. Mark what you know (fasting or incomplete), pick the logging back up, and the system meets you there.