It’s 11am and you genuinely cannot remember whether you stopped eating at 8pm or 9pm last night. You’re doing 16:8 — or you think you are — but the whole thing lives as a vague guess in the back of your mind, one more tab open in a brain that already has forty. So you either break early “just in case,” or you grind through an extra hour of low-grade willpower tax, never quite sure the discipline is even buying you anything.
The short version: Zero is a free, freemium app that tracks your intermittent-fasting windows for you. You tap to start a fast and tap when you eat; it logs the duration, your streak, and your patterns over time, and syncs with Apple Health and Google Fit so your fasting data sits next to your sleep, steps and heart rate. The paid tier, Zero Plus, runs $8.99 a month or $69.99 a year and adds deeper analytics and an ad-free experience — but the free version is genuinely enough for most people. It’s best if you already fast and want honest feedback without the mental overhead of remembering, guessing and doing the maths in your head.
What does Zero do? It takes fasting tracking off your mind
Intermittent fasting asks for discipline. Tracking it shouldn’t ask for any. Yet most people run their fast on a kitchen timer or pure memory — and both quietly drain the same focus they were trying to protect. Zero’s entire job is to carry that load for you.
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You tell the app when your fast starts; it ends when you log your first food. In between, it tracks:
- Fasting duration, down to the minute.
- Your streak — consecutive days you’ve hit a fast.
- Estimated calorie burn during the fasted window.
- Whether your fast lines up with your sleep and circadian rhythm.
- Your history, rolled up into trends across weeks and months.
The appeal is almost embarrassingly simple: you stop thinking about when you’re fasting and just live, while the app keeps the record. The real product here isn’t data — it’s the willpower you get back when you no longer have to remember anything.
Zero’s core features: what actually earns its place
A tracking app is only worth installing if the details are right. A few of Zero’s are.
Automatic time-zone adjustment
Travel scrambles fasting windows in a way most people don’t notice until their gut is confused in a new city. Zero recalibrates your schedule when you cross time zones, so a 16-hour fast stays 16 hours instead of silently becoming 14 or 18 depending on where you landed. Minor until it isn’t.
Apple Health and Google Fit integration
Zero feeds straight into your phone’s native health layer, so your fasting data syncs alongside sleep, steps, workouts and heart rate. If you also run Oura, Whoop, Strava or Apple Fitness+, Zero’s numbers flow into the same picture — which is what makes it genuinely useful for anyone trying to see whether their fasting tracks with sleep quality or training.
Statistical breakdowns
The app shows you patterns you’d never spot by feel: your average window, your longest streak, your most common protocol (16:8, 18:6, 20:4, OMAD), and how consistent you actually are versus how consistent you think you are. It also flags when your fasts align best with your circadian rhythm.
Educational content
Zero bundles articles and expert material on fasting protocols and the science underneath them. For a newcomer unsure whether 16:8 or 20:4 fits their life, this is the difference between copying a trend and understanding a lever. The tone stays grounded in published fasting research rather than hype — which, in this category, is rarer than it should be.
The turn: the app isn’t the intervention — your consistency is
Here’s what’s easy to get backwards. People download a fasting tracker expecting the app to deliver the result, the way you’d expect a pill to. It won’t, and no honest review should pretend otherwise. Zero doesn’t burn a single calorie for you. It doesn’t decide what you eat when the window opens.
What it actually changes is the thing that quietly decides whether fasting works at all: your consistency. The reason most fasting attempts fail isn’t a flawed protocol — it’s the slow erosion of remembering, the early breaks “just this once,” the weeks where you genuinely can’t tell if you stuck to it. Seeing a six-day streak on a screen does more to keep you fasting than any amount of motivation, because it turns an invisible habit into a visible one you don’t want to break. That’s the lever. The app is just the thing that makes the lever pullable.
What’s behind the Zero Plus paywall? The freemium model, honestly
Zero’s free tier is functional, not a crippled demo. You get full tracking, the core statistics and the health integrations without paying.
The Plus subscription — $8.99 a month or $69.99 a year — adds:
- Advanced trend analysis, with deeper pattern recognition across months.
- Customisable fasting goals and protocols.
- Priority support.
- An ad-free experience.
The paywall is there, but it isn’t aggressive. You can fast seriously for as long as you like on the free plan. Plus earns its money only if you want to squeeze every last insight out of your history or you’re simply tired of the occasional ad. For most people, the honest answer is to run the free version first and only upgrade if you catch yourself wanting analytics you don’t currently have.
The friction point: the notifications are loud by default
Zero ships with notifications on, and they’re persistent — reminders when your window ends, when you’re approaching your goal, when you break your fast. If you’re sensitive to app pings (and on a sovereignty-minded site, you should be), this is the one thing to fix on day one. Open the settings, trim the alerts to the one or two that actually serve you, and the app fades quietly into the background where it belongs.
How does Zero compare to manual tracking and rivals?
If you currently log fasts in Apple Notes or a spreadsheet, Zero removes the repetitive entry — worth it if consistency is your weak point. If you run a kitchen timer, Zero adds the historical layer you’ve been missing entirely.
Competing apps like Fastic and various “intermittent fasting” trackers exist, but they tend to lean heavier on coaching upsells and ads. Zero is cleaner and more data-focused. If Apple Health or Google Fit is already your main health dashboard, Zero’s tight integration makes it the obvious pick rather than a close call.
Who is Zero actually for?
- Biobad actors who want to correlate fasting with sleep, HRV and metabolic markers — the integrations make that picture possible.
- People fasting for weight loss, where accountability is the whole game and a visible streak provides real feedback that you’re on track.
- Longevity and autophagy-minded users, who can use the circadian-alignment view and trend stats to time their windows more deliberately.
- Frequent travellers, for whom the automatic time-zone handling is a genuine quality-of-life win.
What Zero deliberately doesn’t do
Zero tracks fasting duration. It does not track calories, macros, food quality or nutrient timing — and that’s a design choice, not an oversight. It’s a fasting tool, not a meal planner. If you need calorie counting, you pair it with something like MyFitnessPal. That modularity is honestly cleaner than the bloated all-in-one apps that do ten things adequately and nothing well.
Zero also offers no medical advice, and this is the part to take seriously. It won’t tell you whether fasting is safe for your situation. If you’re on medication, have any history of disordered eating, are pregnant, or manage a chronic condition, talk to a doctor before using fasting as a protocol — a tracking app is not a clinician, and it isn’t trying to be.
The first week with Zero: what to actually expect
The first few days are mostly about un-learning the guesswork. You’ll catch yourself reaching for the phone to check a number you used to estimate, and that’s the point — the estimating was the leak. Start a fast when you finish dinner, log your first food the next day, and let the app do the arithmetic you’ve been doing badly in your head.
By the end of week one you’ll have something you’ve probably never had before: an honest record of how consistent you really are. For a lot of people that’s a quiet shock — the 16:8 they were sure they ran turns out to be closer to 14:10 most days. That’s not failure; it’s the first useful data point. Now you can close the gap deliberately instead of guessing at it.
A practical caution worth stating plainly: a visible streak is motivating, but don’t let the number itself become the goal. Fasting is a tool, not a score to defend. If a longer fast leaves you light-headed, irritable or obsessive, the right move is to break it and shorten the window — not to protect a streak at the cost of how you actually feel. The app should serve your body, never the other way around.
Frequently asked questions
Is Zero free, or do I have to pay?
Zero is free with an optional Plus subscription at $8.99 a month or $69.99 a year. The free version includes full fasting tracking, statistics and health integrations. Plus adds advanced analytics and removes ads. Most people never need to upgrade.
Does Zero work with both iPhone and Android?
Yes. Zero integrates with Apple Health on iPhone and Google Fit on Android, so it works across both ecosystems and syncs your fasting data to whichever health platform your phone already uses.
Can I use Zero for different protocols on different days?
Yes. Because you start and end each fast manually, Zero adapts to whatever you’re doing that day — 16:8 one day, 20:4 the next. It tracks your actual behaviour rather than locking you to a fixed schedule.
Does Zero help you lose weight?
Zero tracks fasting compliance; it does not guarantee weight loss. Weight change depends on your overall calorie balance, food quality, sleep and stress — not the tracking app. What Zero does is help you stay consistent with your fasting window, which is one lever inside that bigger system.
What if I forget to log when I break my fast?
You can edit fast start and end times after the fact. Zero lets you go back and correct previous entries, so a missed tap doesn’t lose your data.
Related reading
You opened this review because the not-knowing had quietly become its own tax — the 11am guesswork, the early breaks, the nagging sense that all that discipline might not even be landing. That tax is the thing worth removing first. Let an app hold the record, fix the noisy notifications on day one, and what’s left is the actual practice: you, fasting, with a visible streak you don’t want to break and your sleep and training sitting right beside it.
You were never bad at fasting. You were just doing it blind. The shift here is small but it changes who you are in the habit — you stop being the person hoping the discipline is working and become the person who can simply see that it is, the owner of your own data rather than a guesser inside your own routine. Install it, tame the notifications, and you’ve already taken the first step: a habit you can see is a habit you can keep, and a habit you can keep is sovereignty you don’t have to fight for.
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