An intermittent fasting app that shows you what's actually happening inside your body. Real-time phase tracking, AI coaching, and a smart fasting timer — free on iOS & Android.
Free · No subscription required to start
Fasting Timer
Track your journey
STARTED
Today
10:00 PM
FINISH
Tomorrow
2:00 PM
Most fasting apps just run a timer. ONE shows your exact metabolic phase: Digesting → Burning glycogen → Fat burning → Deep fat burn → Extended fast — updated live as your fast progresses.
A Premium feature powered by OpenAI. Your AI Coach analyses weekly and monthly patterns, tracks Autophagy Efficiency, Fasting Tolerance, and Consistency Score, then gives you a personalised next step.
Quick Start durations, a fully custom timer, and Apple Health / Google Health Connect sync mean fasting fits around your life — not the other way around.
Know exactly where you are in your fast. The timer doesn't just count down — it shows you which metabolic phase you're entering, so you know when fat burning starts and when autophagy kicks in.
Fasting Timer
Track your journey
STARTED
Today
10:00 PM
FINISH
Tomorrow
2:00 PM
Current Phase
Digesting (Absorptive)
Body Status
What You May Feel
Smart Tips
→ Stay hydrated with water
→ Avoid heavy snacking now
→ Prepare for your fast window
Go beyond the countdown. ONE shows your real-time metabolic state — what your body is doing right now, how your insulin levels are trending, and whether autophagy has kicked in.
A Premium feature powered by OpenAI. Every week and month, ONE analyses your fasting patterns and gives you a concrete next step to improve your results — not just raw data.
✦ AI Coach
Autophagy Efficiency
Fasting Tolerance
Consistency is what makes intermittent fasting work. ONE keeps you on track with a day-streak counter — so you can see your progress building over time.
Unleash your power,
Alex!
Ready to continue your fasting journey?
0
Day Streak
Daily Goal
0.0 / 16h
16h to go
Weekly Progress
Hours fasted this week
Updated live
Core fasting features are free forever. The AI Coach and protein tracking unlock with Premium. Current subscription options are shown inside the app.
Most fasting apps are just countdown timers. ONE is built around what actually happens inside your body.
| Feature | ONE | Zero | Fastic | DoFasting |
|---|---|---|---|---|
| Fasting Timer | ✓ | ✓ | ✓ | ✗ |
| Real-Time Metabolic Phases | ✓ | Paid | Limited | ✗ |
| Live Body Status Dashboard | ✓ | Paid | ✓ | ✗ |
| Autophagy Tracking | ✓ | Paid | Limited | ✗ |
| AI Coach | Paid | Limited | Limited | ✗ |
| Free Without Subscription | ✓ | ✓ | ✓ | ✗ |
| iOS & Android | ✓ | ✓ | ✓ | ✓ |
| No Ads | ✓ | ✓ | ✗ | ✗ |
Based on free tier as of 2025. “Paid” = requires subscription. “Limited” = basic version only on free tier. DoFasting has no free tier — all features require a paid subscription. Subject to change.
Free from the App Store or Google Play. No account required to start — just open the app.
Pick a Quick Start — 16h, 19h, 24h, or 36h — or set a fully custom fasting window that fits your life.
ONE tracks your metabolic phases, surfaces AI insights, and keeps your streak alive — automatically.
Want to learn more first?
The intermittent fasting app that works — free to download, no subscription to start. Available on iOS and Android.
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