Fasting is hard.
Failing isn't your fault.
Most people don't quit fasting because they lack willpower. They quit because nobody told them hunger passes in 20 minutes, that the headache at hour 16 is salt, or that starting at 16 hours was never realistic. KeepFasting replaces willpower with a system.
Free · No account · Your data never leaves your phone
Good evening
One more hour is one more hour your body isn't storing fat.
Liver glycogen is running low, so your body ramps up fat oxidation and starts making ketones. Fat stores — including visceral fat —…
You didn't lack discipline.
You lacked a system.
Almost every failed fast comes down to one of seven moments. Each one is predictable — and each one is engineered out of this app.
See what happens
inside your body
Drag through a fast and watch the stages change. This is the same timeline the app shows you live, hour by hour — so you always know why you feel the way you do.
Drag to move through the fast
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0–4 h—
Everything aimed at one thing:
finishing the fast you started.
No calorie counting. No meal plans. No leaderboard. Just the things that actually decide whether you make it to your goal.
A ladder, not a cliff
Eleven levels from 8 hours to 3 days. Complete a level twice and the next unlocks. Nothing above 24 hours is ever selected for you, and 72 hours+ is marked supervised-only.
Know what's happening
A live readout of the metabolic stage you're in — fed, early fasting, fat burning, ketosis, deep, extended — with a plain-language explanation and the time until the next one.
Craving SOS
One tap when you're about to quit. A 10-minute wave timer, a checklist that actually works — water, salt, a short walk, breathing — and your personal reason, right at the moment of temptation.
Track the fat that matters
Visceral fat around your organs is what drives disease risk, and it's the first to go. Keep your waist under half your height — the app charts the ratio and tells you where you stand.
Streaks that forgive
A 30-day consistency grid, weekly commitments you set yourself, and 17 achievements. Miss a day and the streak survives, because coming back is the skill that matters.
14 articles, zero hype
Electrolytes, exercise, sleep, how to break a fast, supplements worth taking (almost none), notes for women, plateaus. Every claim carries its citation. Where the evidence is thin, it says so.
Nudges at the right hour
Milestone alerts at 12, 16, 24, 48 and 72 hours that tell you what just changed in your body. Electrolyte reminders on long fasts. A daily start reminder if you want one.
Nothing leaves your phone
No account, no sign-up, no cloud, no analytics, no ads. Your fasts, weight and measurements are stored on your device and nowhere else.
Every claim here
has a paper behind it.
Fasting attracts a lot of nonsense. This app cites its sources, and where the research is preliminary or animal-only, it says so plainly instead of selling it to you.
Fasting shrinks visceral fat, and visceral fat is the one that matters
The fat around your liver, gut and heart is metabolically active — it drives inflammation and insulin resistance, and it's linked to type 2 diabetes and heart disease even at a normal body weight. It also responds first to an energy deficit.
The metabolic switch happens around 12–16 hours
For roughly the first 12 hours you burn liver glycogen. As it runs down, fatty acids and ketones take over as your main fuel. Ketones aren't just energy — they act as signalling molecules that reduce inflammation.
Time-restricted eating improves metabolic health without counting calories
Controlled trials of 16:8 and earlier eating windows show reductions in weight, insulin resistance and blood pressure. Total intake still matters — fasting simply makes a deficit easier to hold.
Hunger is a wave, and it passes on its own
Ghrelin rises in anticipation of your habitual meal times and subsides within about 20 minutes regardless of whether you eat. On multi-day fasts it decreases over time — most people report day 2 is easier than day 1.
Most fasting side effects are sodium, not starvation
Falling insulin increases sodium and water excretion by the kidneys. That's the mechanism behind the classic hour-16 headache, fatigue and light-headedness — and why a little salt fixes it.
Lifting weights decides whether you lose fat or muscle
Without resistance training, a meaningful share of weight lost can be lean mass. Training two to three times a week plus adequate protein preserves muscle while the fat comes off.
Systems beat willpower — this is measurable
If-then plans roughly double or triple follow-through on a goal. People who self-monitor lose about twice as much weight as those who don't. Both are built into the app rather than left to you.
Fasting isn't for everyone,
and this app says so.
An app that pushes you to fast harder has a duty to tell you where the limits are. These warnings are in the onboarding, not buried in a settings screen.
⚠️ Talk to a doctor first if you are
- Pregnant, trying to conceive, or breastfeeding
- Type 1 diabetes, or taking insulin or sulfonylureas
- History of an eating disorder
- Underweight (BMI under 18.5)
- Under 18 years old
- Taking medication that must be taken with food, or blood-pressure medication
- Kidney, liver or heart disease, or gout
🛑 Stop and eat immediately if you feel
- Dizziness, fainting or near-fainting
- Heart palpitations or chest pain
- Confusion or severe weakness
- Persistent nausea or vomiting
🛡️ Built-in limits
- Fasts over 24 hours show a warning before you can select one
- 72 hours+ is marked supervised-only and is never chosen for you
- Refeeding syndrome risk is explained before any multi-day fast
- Craving SOS separates “this will pass” from “this is a warning sign”
- No leaderboards, no longest-fast competition, no pressure to go further
In your language.
All 31 of them.
Every screen, every article, every notification — fully translated, including right-to-left layouts for Arabic and Hebrew. The app follows your iPhone's language automatically.
Your next fast is the one that counts.
Start at a level you can win tonight, and climb from there.
Get KeepFastingiPhone · iOS 17 or later · Free