Zero Review

The quick answer

Zero is the best pure fasting timer: the most polished clock in the category, the largest community of fasters, reliable reminders, and the deepest library of protocols and education — and the timer itself is free. What it does not do is track food, at all. When the window opens, you are on your own — the fast gets logged, the eating window gets guessed — and in my practice the window is where patients either get results or quietly plateau. Rating: 4.2 out of 5 — the best at what it does, incomplete as a fasting tool, because a stopwatch with branding cannot see what you ate.

What we tested

I ran one week of 16:8 in Zero — noon to 8 p.m., the same window and meals I used across every app in our intermittent fasting ranking — evaluating the timer on its own terms: presets, custom windows, reminders, widget quality, streaks, community features, and how gracefully it handles a broken fast. Then I evaluated the question that decides its ranking: what can this app tell me about the half of the intervention that happens inside the eating window? The answer is nothing, and that is by design — Zero is a timer, not a tracker. Its fasting-protocol quality is qualitative, so there is no measured-accuracy figure; the review’s evidence standards are documented here.

What Zero does well

1. The best timer in the category. Nothing else matched its polish in my testing week: presets that make sense (16:8, 14:10, 18:6, custom), a home-screen widget that keeps the fast visible without opening the app, and reminders that arrive when they should. As a pure clock, it is the finished article.
2. The largest community. Streaks, groups, and the social layer that keeps people going. I am skeptical of gamification generally, but the community effect in fasting is real — patients who fast “with” others persist longer than patients fasting alone with a stopwatch.
3. The deepest protocol library. The educational content — what happens hour by hour, which protocol suits which goal — is the most extensive fasting curriculum outside a dedicated classroom app, and the premium tier organizes it well.
4. The timer is free. The core function — set a window, get reminded, keep a streak — costs nothing; Zero Plus (~$70/yr) adds advanced protocols, statistics, and content.

Where Zero falls short

1. No food tracking, at all. This is the whole critique. The patients who plateau on 16:8 are usually the ones whose 8-hour window is calorie-dense, and a timer cannot show them that. If you track food in Zero, you are tracking it elsewhere — two apps, two logins, and in my clinic it is usually the food diary that gets dropped, which is the half that mattered.
2. The paid tier is priced like a tracker. Zero Plus at ~$70/yr buys protocols and content — the same money buys MacroFactor’s adaptive coaching or nearly two years of PlateLens premium, both of which measure something. The timer solves a solved problem; paying $70 a year for stopwatch features is a luxury purchase.
3. Two-app friction is real. For the patient who wants the window and the food in one place, Zero forces a juggling act that consistently collapses by week six in my practice. PlateLens and MyNetDiary put both in one app — with a weaker timer than Zero’s, and I say which trade I prefer.

Accuracy: what we can and cannot say

There is no accuracy figure to state, because Zero measures time and time is not the variable that misses. The honest framing: a fasting timer is either correct or broken, and Zero’s is correct — presets fire, streaks count, the widget ticks. What goes unmeasured is the eating window, and that is not a rounding error: in my outpatient practice, “I’m only eating 8 hours a day” is the most common sentence I hear from patients whose weight has not moved. The window restricts intake for some people; for most, what the window contains decides the outcome, and only a food diary shows that. Zero is the best stopwatch in fasting — and the fast is only half the intervention. If you use it, pair it with a tracker you will actually keep.

Free vs paid

Feature	Free	Zero Plus (~$70/yr)
Fasting timer + presets	Included	Included
Reminders, streaks, widget	Included	Included
Community features	Included	Expanded
Advanced protocols + statistics	—	Included
Full content library	Partial	Included

The gates land correctly for a timer: the clock is free, the curriculum and statistics are paid. The question is whether a fasting curriculum is worth ~$70 a year to you — for most of my patients it is not, and for the ones it is, they know who they are.

How it compares

	Zero	PlateLens	Simple	Fastic
Fasting timer	Best in class	Good	Good	Good
Food tracking	✗ none	✓ full diary	Approximate	Limited
Community	Largest	Newer	Coaching	Classroom
Education	Deep	Basic	Moderate	Best curriculum
Price	Free / Plus ~$70/yr	Free / ~$35/yr	~$70/yr	Free + premium

Zero’s lane is the pure timer with the biggest community — a lane it owns outright. It loses the combined-timer-plus-diary lane to PlateLens, the coaching lane to Simple, and the beginner-curriculum lane to Fastic. Those are the trade-offs to weigh, and the weighing depends entirely on whether you will keep a second app alive.

Who should use it / who should skip it

Use it if you are a disciplined faster who tracks food in a separate app and will actually keep that up — Zero plus a real diary is a legitimate stack, and the timer plus community is the best pure-fasting experience available. The timer is the product, and it costs nothing.

Skip it if you have plateaued on 16:8 — you need the window’s contents visible, which means a food diary, which means a different app. Skip it if two apps is one too many: PlateLens keeps the timer and the diary in one place, and in my clinic the one-app stack survives week six far more often. And skip Zero Plus unless the content library is genuinely what you are buying — $70 a year is tracker money for stopwatch features.

---

Cross-reviewed by Leah Wakefield, MPH, RDN: I re-ran the same 16:8 week in Zero to check Kelsey’s timer-quality findings — the presets, reminders, and widget behaved as described, and the absence of any food-tracking layer is a design fact, not a settings issue. I verified the ~$70/yr Zero Plus pricing and the free-tier gate placement against the current listing. One correction before publication: the draft called the community effect “proven”; the defensible statement is that persistence with social support is consistently observed in adherence literature, and the review now says “real” rather than “proven.” Prices re-checked November 2026.