Stages, not
streaks.
A field-grade tracker for extended water fasts — 24, 36, 48, 72+ hours. Phase-aware timing, ketone logging, and private session records. Built for self-experimenters running protocols, not counting calories.
Four stages, mapped.
Autophagy
Cells recycle damaged proteins and organelles. The cleanup process Ohsumi won the 2016 Nobel for.
Pick your duration.
Single-night fast. Lands in early ketosis. Daily cadence possible.
The free, signature protocol. Spans a full night plus a day. Reaches autophagy.
Two full nights. Sustained autophagy. Common biohacker baseline.
Stem-cell regeneration ramps. Growth hormone peaks. The peak of the protocol.
The full set of readouts.
Phase-aware tick
The timer knows where you are. Stage transitions cross into colored chrome — not a number changing on a flat dial.
Live Activity
Lock Screen and Dynamic Island become the instrument. A glance: stage, ring, time to next phase.
Apple Watch
Wrist readout, no phone required. Complications + raise-to-wake stage indicator.
Local-only history
Every fast saved on-device. No cloud, no leaderboards, no body data leaving your phone.
Health sync
Optional one-way export to Apple Health: fasting hours, ketone notes, session range.
The Science reference
In-app library citing published autophagy, GH, and metabolic-switch literature. No bro-science.
Six common questions.
No. Fast36 is educational instrumentation. Extended fasts have real risks (electrolyte disturbance, refeeding syndrome, contraindications for medication). Consult a clinician before attempting fasts beyond 24 hours.
Other apps optimize for 16:8 daily compliance. Fast36 is built for the 24-to-72+ hour arc — different physiology, different stages, different UI requirements. The product opinion is that streaks gamify the wrong thing.
On your device only. SwiftData local store. No account, no cloud, no analytics on session data. Optional one-way export to Apple Health.
The free 36h protocol works fully on iPhone. Watch, Live Activity, and Health sync are the long-tail conveniences that justify Pro for the people who actually run the longer protocols.
Yes — manual entry per session in Pro. Future: Bluetooth meter integration (Keto-Mojo, Lumen, etc) on the roadmap, no ETA.
Not planned. iOS-only by design — Live Activity, Dynamic Island, Watch are core to the instrument feel.