Fast Slow vs Ayuna
Price, ratings, monetisation and update history for both apps, side by side — with what reviewers say about each.
Fast Slow
Understand your body's metabolic changes during fasting with a visual timeline. This free app guides you through different fasting zones, from digestion to deep ketosis, and offers customizable schedules and smart notifications. It provides stats, streaks, and widgets for easy progress tracking.
- Fasting timer with visual timeline
- 6 customizable fasting schedules
- 5 distinct fasting zones explained
- Smart notifications for fasting windows
- Stats, streaks, and trends tracking
- Home and Lock Screen widgets
- Siri Shortcuts integration
Read full descriptionHide full description
See what happens inside your body as you fast. Fast Slow walks you through 5 fasting zones, from digestion through fat burning to deep ketosis, so you understand what every hour of your fast is doing. 100% free. Every feature. No ads. No paywalls. No trackers. Free forever. WHAT MAKES FAST SLOW DIFFERENT Most fasting apps just count down a timer. Fast Slow shows you what's actually happening in your body at each stage: - Anabolic (0-4h): Digesting and storing nutrients - Catabolic (4-8h): Tapping into energy reserves - Fat Burning (8-12h): The metabolic switch - Ketosis (12-16h): Ketones and cellular cleanup - Deep Ketosis (16h+): Deep cellular renewal Tap any zone to learn more about the science behind it. 100% FREE. EVERY FEATURE INCLUDED. No premium tier. No trial that expires. No paywall gates. Every feature in Fast Slow is yours from day one: - All 6 fasting schedules - All stats, streaks, and trends - All widgets (Home Screen and Lock Screen) - All notifications - Siri Shortcuts - iCloud sync - Data export Everything free. No catches. FEATURES Fasting Timer One tap to start. One tap to stop. A visual timeline shows where you are, what zone you're in, and what comes next. 6 Fasting Schedules 12:12 for beginners, 14:10, 16:8 (the most popular), 18:6, 20:4, and OMAD (one meal a day) for experienced fasters. Visual Timeline Color-coded timeline of your fasting and eating windows. Plan meals, training, and recovery at a glance. Smart Notifications 7 notification types: goal reached, halfway there, one hour left, eating window alerts, and a custom last meal reminder. Nudges, not nags. Stats & Streaks Total fasts, average duration, personal records, weekly trends, and a monthly fasting calendar. Small wins add up. Widgets Home Screen and Lock Screen widgets with progress rings, timelines, and live timers. Check your fast without opening the app. Siri Shortcuts "Hey Siri, start my fast." Start, stop, and check your fasting status hands-free. AI-Powered Greetings On supported devices, Apple Intelligence creates personalized messages based on your fasting progress, streak, and time of day. iCloud Sync Your fasting data syncs automatically across all your devices. Data You Own Export your fasting history as JSON. Delete everything with one tap. Your data, your choice. DESIGNED FOR REAL LIFE Pick a schedule, adjust as needed, and let Fast Slow handle the timing. New to fasting or already have a routine, it works either way. Structure when you want it, out of the way when you don't. Built by one developer who fasts every day. No corporate agenda. No growth hacking. A well-made tool that respects your time and your data. RESPONSIBLE APPROACH Intermittent fasting can support weight management, energy, and focus, but results vary. Fast Slow provides tools and information, not medical advice. If you have health conditions, are pregnant, or have a history of eating disorders, please talk to a healthcare professional before starting. Terms of Use: https://www.apple.com/legal/internet-services/itunes/dev/stdeula/ Privacy Policy: https://cernezan.com/fast-slow/privacy/
Ayuna
Read full descriptionHide full description
Ayuname follows your intermittent fast and explains, hour by hour, what each phase is said to involve. It is educational information: the app counts time, it does not measure anything about your body. THE FASTING PHASES, EXPLAINED • Fed state (0h): digestion under way • Drawing on stores (4h): the body uses what it has stored • Fat burning (12h): a greater use of stored fat is described • Early ketosis (16h): ketone bodies appear • Full ketosis (18h): ketones matter more as fuel • Autophagy (24h): cellular recycling, studied mostly in animals • Prolonged fast (36h) • Three-day fast (72h): usually done with supervision THE PLAN THAT FITS YOU 16:8, 18:6, 20:4, OMAD and long fasts. Change it whenever you want. YOUR FULL HISTORY Every fast, your streaks and months of progress. AN ALERT AT EVERY PHASE We tell you when the timer reaches a new phase. YOUR DATA IS YOURS Works without an account. With one, your history survives a new phone. Free, no ads. Optional premium features. Ayuname is a wellness app: it is not a medical device, it does not diagnose or treat any condition, and it is not a substitute for medical advice. Talk to your doctor before fasting, especially if you are pregnant, taking medication or living with a medical condition.
Screenshots
Verdict
The clearest difference is device support: Ayuna at 3 against Fast Slow's 1. Ayuna also leads on iOS requirement (15.1 vs 18.0). On price, update cadence, ads and in-app purchases there is nothing between them.
Scored on Price · Rating · Positive reviews · Number of ratings · Update frequency · Ads · In-app purchases · Monetization · Best chart rank · Devices · Requires iOS
Both are free to download. Fast Slow sells 4 in-app purchases, starting at $1.99 per 7 days and Ayuna sells 2 in-app purchases, starting at $2.99 per month. Whichever you choose, the download price is not the number that matters.
Fast Slow ships an update every 2 weeks, Ayuna every 8 days. The most recent releases landed on October 24, 2026 and October 31, 2026 respectively.
| Parameter | Fast Slow | Ayuna |
|---|---|---|
| Price | Free | Free |
| Rating | 5.0 (39 ratings) — better | — |
| Positive reviews | 100.0% of reviews | — |
| Number of ratings | 39 — better | — |
| Update frequency | Every 2 weeks | Every 8 days — better |
| Ads | No | No |
| In-app purchases | Yes | Yes |
| Monetization | Free | — |
| Devices | iPhone | iPhone, iPad, iPod — better |
| Requires iOS | 18.0 | 15.1 — better |
| Further details — not scored | ||
| Size | 23 MB | 43 MB |
| Age rating | 4+ | 4+ |
| Developer | Zan Cerne | WEB3 SOLUTIONS LLC |
In-app purchases
Fast Slow
- Legacy$1.997 Days
- Legacy - Yearly3 Days trial$12.991 Year
- Buy Me a Coffee$2.99
- You're Amazing$9.99
Ayuna
- Premium Monthly$2.991 Month
- Premium Yearly3 Days trial$19.991 Year









