KETHOS
Extended Fasting, Done Right
Free · Designed for iPad. Not verified for macOS.
Now with custom fasts up to 10 days, guided refeeding, and a science-backed timeline from ketosis to stem cell activation. Powered by American Fitness.
Kethos is the extended fasting companion built for people who are serious about going beyond 16:8.
Whether you're chasing fat loss, deep autophagy, an immune reset, or longevity, Kethos guides you through every hour of your fast — from the metabolic switch at 12 hours to stem cell activation past day five — with a clean, focused timer and education grounded in the latest research.
Powered by American Fitness.
THE FASTING TIMELINE, LIVE
Watch your body move through six distinct phases as you fast:
• Fed State (0–12h) — Glycogen depletion
• Fat Burning (12–24h) — The metabolic switch
• Ketosis (24–48h) — Autophagy activates
• Deep Ketosis (48–72h) — Brain on ketones
• Autophagy (72–120h) — Peak cellular cleanup
• Stem Cells (120h+) — Deep regeneration
Each phase shows your estimated ketone levels, growth hormone response, autophagy activity, and what's happening in your body — so you always know why you feel the way you do.
BUILT FOR EXTENDED FASTS
Most fasting apps stop at 24 hours. Kethos starts there. Choose a custom fast anywhere from 24 hours to 10 days, or pick a preset for your goal:
• Fat Loss — 16–24h fasts, 2–3× per week
• Cellular Repair — 24–48h fasts every 2 weeks
• Immune Reset — 72+ hour quarterly fasts
• Metabolic Health — Daily 16:8
• Longevity — Mixed protocol with periodic extended fasts
GUIDED REFEEDING
Breaking an extended fast matters as much as the fast itself. Kethos walks you through a structured refeeding protocol so you reintroduce food safely and protect the work you put in.
LEARN AS YOU FAST
A built-in education library covers what every extended faster should know:
• What autophagy actually is
• Why electrolytes make or break a long fast
• Understanding ketosis and BHB
• Refeeding syndrome and how to avoid it
• Sleep changes during fasting
• When exogenous ketones help — and when they don't
CHECK IN WITH YOURSELF
Log how you feel during your fast with quick symptom check-ins. Track energy, hunger, mental clarity, and any side effects so you can fine-tune future fasts.
YOUR FASTING JOURNEY
• Streaks and completion tracking
• Full history of every fast you've completed
• Shareable summary cards for milestone fasts
• Phase milestone notifications so you never miss the moment your body shifts gears
Kethos is powered by American Fitness. Learn more at american.fitness.
Kethos is for educational and tracking purposes only. Extended fasting is not appropriate for everyone. Consult a qualified healthcare provider before beginning any fasting protocol, especially fasts longer than 24 hours, or if you are pregnant, breastfeeding, taking medication, or have a medical condition.
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The developer, Strategic Services Group, LLC, indicated that the app’s privacy practices may include handling of data as described below. For more information, see the developer’s privacy policy .
Data Not Collected
The developer does not collect any data from this app.
Accessibility
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Information
- Seller
- Strategic Services Group, LLC
- Size
- 3.2 MB
- Category
- Health & Fitness
- Compatibility
Requires iOS 18.0 or later.
- iPhone
Requires iOS 18.0 or later. - iPad
Requires iPadOS 18.0 or later. - Mac
Requires macOS 15.0 or later and a Mac with Apple M1 chip or later. - Apple Vision
Requires visionOS 2.0 or later.
- iPhone
- Languages
- English
- Age Rating
9+
- 9+
- Contains
Health or Wellness Topics
- Copyright
- © American Fitness, LLC