Fast36 vs FastZen

Stages, not streaks. Fast36 is the fasting app for people who care about the metabolic arc, not the calendar grid. Track the biochemical progression of a 24 to 72+ hour fast with phase-aware timing, in-the-moment science, and a private record of every session. WHAT YOU GET • Stage-aware timer. Watch your fast move through the four metabolic regimes — glycogen depletion, ketosis, autophagy, deep autophagy — with color-coded thresholds that match real human physiology. • Quick Log for ketones and glucose. Pair every fast with a finger-stick reading. Build a longitudinal record of how your biomarkers respond to each protocol. • Live Activity on the Lock Screen. Current stage, elapsed time, and next threshold — always one glance away. No need to open the app. • Apple Watch companion. Start, monitor, and end fasts from your wrist. Phone, iPad, and watch always show the same session. • History with substance. Total hours, per-stage distribution, per-fast gantt, readings, notes. No streaks. No flame emoji. No celebratory confetti. • The Science reference. Peer-reviewed citations for every stage claim. We tell you what's proven in humans and what's extrapolated from rodent studies, and when evidence is emerging rather than settled. FREE • 36-hour protocol — the namesake fast • Stage-aware timer and Stages reference • History log and HealthKit integration • On-device privacy FAST36 PRO — $14.99 / month or $99 / year • 24-hour reset fasts • 48-hour and 72-hour extended protocols • Custom fast lengths • Live Activity with stage transitions • Stage-crossing haptics • Apple Watch companion • Quick Log for ketones and glucose • Full history analytics and stage distribution chart • Notes on every fast • Apple Health bidirectional sync • The Science deep-dive with citations WHO IT'S FOR Biohackers running 24 / 36 / 48 / 72-hour protocols. People who want their fasting app to read like a lab notebook, not a game. Anyone who has ever said "autophagy" at dinner and meant it. Not for calorie counting, not for weight-loss streaks, not for "gamified wellness." PRIVACY All fasting data lives on-device. Optional Apple Health sync stays between you and Apple — it does not pass through our servers. No accounts, no newsletters, no behavioral tracking, no third-party analytics. Not medical advice. Extended fasting carries real risks for people with diabetes, eating disorder history, pregnancy, low body fat, or on medications affecting blood sugar or blood pressure. Consult a clinician before attempting any fast over 24 hours. Fast36 Pro subscriptions renew automatically unless cancelled at least 24 hours before the current period ends. Manage or cancel from your Apple ID settings. Terms of Use: https://fast36.app/terms Privacy Policy: https://fast36.app/privacy Support: hello@fast36.app

FastZen tracks your fast and lets you move one date without rewriting your weekly routine. Dinner running late? Adjust that day and keep the rest of your week. Preview the next 7 days, including start times, planned finishes and rest days. • Start a 16:8, 18:6, 20:4 or OMAD (23-hour) fast. • Set a custom duration from 1 to 48 hours. • See elapsed time, remaining time and your planned finish. • Review completed sessions and correct their times. • Repeat one start time on the weekdays you choose. Your active session stays saved when you close the app. No account, no ads and no server sync. The widget puts your fast on the Home Screen. On iPhone, a Live Activity shows your session on the Lock Screen for up to 8 hours, the iOS limit. The session stays saved in the app. FastZen is a tracking tool, not medical advice or a promise of weight loss. Custom Week is a one-time purchase with no subscription. It unlocks a separate plan and start time for each weekday, rest days, and changes to a single date without changing your recurring week. People who used FastZen before version 1.1.0 keep that access without paying.