The fasting app that adapts to your recovery
This workout means fast differently tomorrow.
Every other app is a fasting timer or a recovery tracker. Kairo connects them — so the fast you start today actually fits the body you bring to it.
Fast·Move·Recover
The Kairo loop
Three pillars. One loop. Only Kairo closes it.
FAST
A live timer through 10 metabolic stages — and a daily window that eases when your recovery says so, instead of demanding the same hours every day.
MOVE
Log a workout and Kai answers on the spot with what it means for tomorrow's fast. Training fasted or fed? Your own history holds the answer.
RECOVER
Sleep and heart-rate variability become a readiness score that always shows its why — from Apple Health, with or without a wearable.
Timers tell you how long. Wearables tell you how rested. Kairo owns the sentence in the middle: a workout changes the fast, the fast changes recovery, and recovery changes the next workout.
Fast · Move · Recover
Three pillars — and all three is what makes us different.
Every other app picks one. Kairo runs the whole loop, and each pillar feeds the next. Here's what lives in each.
Fast
The burn, made smart
A fast that fits the body you bring to it — not a stopwatch that demands the same hours every day.
- Adaptive window — eases when your recovery is low, holds when you're primed
- 10 metabolic stages live, each explained with cited science
- Smart data — a proprietary Kairo Score that always shows its why
- Hydration, streaks, Live Activity & Dynamic Island
Move
Your training, understood
Log a workout and Kai answers on the spot with what it means for tomorrow's fast.
- See your workouts — every session read automatically from Apple Health
- Fasted or fed? Your own history tells you which suits you
- Training-aware guidance — hard days cost less recovery as you adapt
- Works with any wearable that writes to Apple Health
Recover
Recovery that's actually smarter
Sleep and heart-rate variability become a daily readiness read — with or without a wearable.
- Smarter recovery — readiness that shapes the right fast for today
- No wearable? Kairo still knows how you slept, because you told it
- Your story — your month, told back in your own numbers
- Recovery Mode: pause the fast, keep the streak, no judgment
The intelligence
Smart where it counts — and private the whole way.
All of it runs on your iPhone. Nothing leaves the device.
Smart notifications
Nudges timed to your fast and your rhythm — never spam, never guilt.
Smart data
One Kairo Score from real signals, explained in plain language — no black box.
Smarter recovery
Sleep & HRV become readiness that adapts today's fast to how you actually feel.
Your workouts
Every session read automatically — and turned into what it means for tomorrow.
Ten metabolic stages
Your body keeps going. Kairo shows you where.
Stage timing varies person to person — Kairo teaches each stage as you reach it, with the research one tap away.
Real screens
No invented UI. No fabricated numbers.
Everything below is the shipping app. Swipe through.
shaped by sleep & HRV — with its why
what your body is doing, hour by hour
your month, told in your own numbers
one tap from the research on PubMed
multi-day journeys that ease off when you need it
the Trust Center — right in the app
the same calm, in warm cream
How Kairo is different
The only one that does all three.
Some apps count your hours. Some read your sleep. Nobody makes the two talk to each other — so the new kid built the one that does.
| The timers count the hours |
The trackers read your body |
Kairo does all three |
|
|---|---|---|---|
| Live fasting timer & stages | ✓ | — | ✓ |
| Readiness from sleep & HRV | — | ✓ | ✓ |
| Reads your workouts | — | ✓ | ✓ |
| Adapts the fast to your recovery | — | — | ✓ |
| Private AI coach, on-device | — | — | ✓ |
| No account, nothing leaves the phone | — | — | ✓ |
| No hardware to buy | ✓ | — | ✓ |
Compatible with what you already own
Native to Apple. Friendly to your wearable.
Already wear something? Keep it. Kairo reads the signals you already collect through Apple Health — no second app, no extra login.
Through Apple Health
Built natively for iPhone, Apple Watch, Live Activities, Siri and widgets — the way an Apple app should feel. Health data is read with your permission and never leaves your device.
Coach Kai
Not another tracker. A coach who remembers.
Kai is a private, on-device AI — built on Apple's own on-device intelligence. He answers from cited research and your own data, hedges when he isn't sure, and says "I don't have enough data yet" instead of making something up. Nothing you tell him ever leaves your phone.
The Kairo standard
Honest by design. Private by default.
No account. Ever.
Nothing to sign up for. Kairo works with the Apple ID already on your phone.
On your device
Your fasts, workouts, journal, and every AI conversation stay on the phone. Optional iCloud sync goes only to your private iCloud.
Real data only
No invented trends, no fake social proof. The Kairo Score never shows a number without showing why.
Cited science
Every scientific claim links to peer-reviewed research — one tap to PubMed.
No ads. No data sales. No tracking. Read the two-minute privacy policy — the short version is: we don't collect your data. Really.
Free to start · Kairo Labs for depth
Premium buys depth, never the timer.
Kairo
Free
forever
- Live fasting timer with all 10 metabolic stages
- Streaks, history & milestone awards
- Hydration, reminders & Live Activity
- Sleep logging in five seconds
- The "Health for Everyone" learning track
A genuinely great fasting app — not a demo.
Kairo Labs
$59.99 / year
about $5 a month · or $9.99 monthly · 7-day free trial on yearly
- Adaptive fasting — the window eases when recovery is low
- Daily readiness from your sleep & HRV
- Coach Kai — private, on-device AI coaching
- Training-aware guidance & explainable trends
- Advanced protocols, multi-day Programs & the full cited library
- Watch & widget extras, milestone cards, Kai's colors
One membership. Every feature included — no add-ons. Cancel anytime; Apple sends the trial reminder.
Questions, answered plainly
The things people actually ask
Do I need an Apple Watch, WHOOP, or Oura?
No. If you wear one, keep its app syncing to Apple Health and Kairo reads those signals automatically — no extra login. If you don't, Kairo still knows how you slept, because you told it — a five-second log tunes today's fast.
What happens to my data?
It stays on your phone. There's no account, no server of ours, no analytics trackers. Optional iCloud sync uses your private iCloud. You can export or erase everything from inside the app. Details in the privacy policy.
Is the AI coach sending my conversations somewhere?
No. Coach Kai runs on Apple's on-device model — the conversation happens on your iPhone's own chip and never leaves it. That's also why he's unlimited rather than metered.
What's actually free?
The whole core loop: the live timer with all ten stages, streaks, history, awards, hydration, reminders, sleep logging, and the learning track. Kairo Labs adds the intelligence — readiness, adaptive windows, Coach Kai, programs, and the full cited library.
Is fasting right for me?
Not always — and Kairo won't pretend otherwise. If you're pregnant, have a history of disordered eating, or manage a medical condition, talk to a professional first. Kairo provides general wellness education, not medical advice.
How do I get it — and when?
A private TestFlight beta is opening soon. Get on the beta list to be first in, or get a ping at launch. The full release is coming to the App Store — iPhone only, and proudly so: Kairo is built natively for iOS, not ported from anywhere.
FAST·MOVE·RECOVER
We work hard because you work hard.
Private. Native. A new player in health, built to earn your trust — and to turn everything you already do into results you can see.
Time to see the results.