You've already bought into cycle syncing — eating and exercising in step with your hormones instead of the same way every day of the month. So you go looking for an app that does the same for fasting, and mostly find the opposite: cycle-syncing apps built around food and workouts, with fasting either missing entirely or bolted on as an afterthought. Yes, there's an app built to close that specific gap — here's why the gap exists and what closing it actually looks like.
The short answer
Yes — FastSyncer is a cycle-syncing app built with fasting as a core feature from the start, not an add-on. It adjusts your fasting window and food guidance to the same four-week hormonal rhythm most cycle-syncing apps already track for workouts and meals. Join the waitlist for free early access when it launches.
Why most cycle-syncing apps leave fasting out
Cycle syncing as a concept — matching food, exercise intensity, and recovery to where you are in your cycle — has been around long enough that a handful of apps and programs cover it well for meals and workouts. Fasting gets left out for a structural reason, not an oversight: a fasting window is a time-based rule (when to eat, when not to), while most cycle-syncing content is built around what to eat and how hard to train, which is a different kind of guidance to design and maintain. Bolting a fasting schedule onto an app built for meal plans and workout intensity means someone has to independently model how the fasting window itself should lengthen or shorten across the same four weeks — and most cycle-syncing products never built that layer, so they either skip fasting or hand you a single fixed window that ignores the cycle they otherwise track carefully.
The result is a real gap: women who already understand and use cycle syncing for food and training are left doing fasting the old way — one flat number, every day, regardless of phase — even though the same hormonal logic that changes what and how hard you eat also changes how long a fast should reasonably run.
What a real fasting layer needs, on top of the cycle syncing you already know
If you're already cycle syncing, you know the basic shape: the days after your period tend to be steadier and more forgiving, the days around ovulation often bring the most energy and metabolic flexibility, and the one to two weeks before your period bring rising progesterone, higher resting metabolic rate, and less stable blood sugar. A fasting layer that actually respects that rhythm needs to do three things: lengthen the window when your hormones support it (the days after your period through ovulation), pull it back in the pre-period stretch instead of holding it fixed, and pair the window itself with food guidance for breaking the fast — protein and fat-forward eating matters more in the luteal phase than earlier in the month, the same logic you're already applying to full meals.
What FastSyncer does for cycle syncing plus fasting together
FastSyncer folds fasting into the same rhythm you're already syncing everything else to. Each day it gives you one card: today's fasting hours based on your actual cycle phase, exactly what to eat to break the fast well for that phase, and the do's and don'ts that go with it right now — fasted exercise, caffeine timing, how hard to push a workout. The fast auto-starts and logs itself in the background, so there's no manual timer and no day-counting on top of everything else you're already tracking, and the whole plan shifts automatically as your cycle moves and as your body changes over time.
What you'd have to do without it
Without a fasting layer built into your cycle syncing, you're left estimating your phase from memory, adjusting a fasting timer by hand based on that guess, separately researching what to break a fast with for that phase, and redoing all of it every month — on top of whatever you're already tracking for meals and training. It's the same kind of manual math that made plain cycle syncing hard before dedicated apps existed for food and workouts, just for the one piece those apps left out.
When it launches and how to get it
FastSyncer is in final testing now and launching soon on the Apple App Store, with Android support to follow. It isn't downloadable yet, so the way to get it first — and for free — is to join the waitlist. Waitlist members get early access as soon as it's live.
FAQ
Is there a cycle syncing app that includes fasting, not just food and workouts? Yes. FastSyncer treats fasting as a core cycle-synced feature — the window itself lengthens or shortens with your hormones, alongside food and do's-and-don'ts guidance for each phase.
Why don't most cycle-syncing apps cover fasting? Fasting requires modeling a time-based window across the cycle, which is a different design problem from the meal and workout guidance most cycle-syncing apps are built around — most never added that layer.
Does the fasting window actually change with my cycle, or is it fixed? It changes. It tends to be longer and more flexible in the days after your period through ovulation, and shorter and steadier in the one to two weeks before your period.
Do I need to already be cycle syncing my food and workouts to use this? No — FastSyncer works as a standalone fasting app. If you're already cycle syncing other parts of your life, it simply adds the fasting piece to the same rhythm.
For the reasoning behind syncing fasting to your cycle at all, how to sync intermittent fasting with your menstrual cycle and best fasting schedule for each phase of your cycle go deeper, and is there an app that syncs fasting to your menstrual cycle? covers the fasting-specific app question directly.