The intermittent fasting app that shows you what's actually happening inside your body. Real-time phase tracking, AI coaching, and a smart fasting timer — rated the best intermittent fasting app by users 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 → Fat Burning → Ketosis → Autophagy — updated live as your fast progresses.
Your AI Coach analyzes weekly/monthly patterns, tracks Autophagy Efficiency, Fasting Tolerance, and Consistency Score, then gives you a personalized next step.
Social Event Planner, Pre-Fast Meal Advisor, and flexible schedule support 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.
Your AI Coach doesn't just show you data — it interprets it. Every week and month, it analyses your fasting patterns and gives you a concrete next step to improve your results.
✦ AI Coach
Autophagy Efficiency
Fasting Tolerance
Consistency is what makes intermittent fasting work. ONE keeps you on track with day streaks, active challenges, and a visual streak calendar — 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
Active Challenges
4 x 14h Week Starter
1 week
No paywalled features. No confusing tiers. Everything ONE does is available from the moment you download.
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 | ✓ | 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 your fasting schedule: 16:8, 18:6, OMAD, or a fully custom 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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