Nesteia: A fasting timer that tells you the truth about your body.
Eleven body stages, each with its sources. A hard 120-hour ceiling.
- No account
- No tracking
- Sources on every stage
Try a plan
Nothing in the phone can pass 120 hours, and the 96 and 120-hour plans run only with a clinician's supervision.
Started Tue 03:11 · ends Thu 03:11 · you choose when to end
Tap the timer to change how it looks.
Stillness is not idleness. A great deal is being sorted out.
Most of the liver's stored sugar has been used. The body now makes almost all its glucose fresh, mainly from fat-derived glycerol and amino acids.
What to do: Two to three litres of fluid a day to thirst, with sodium. Sleep early.
Next: Ketosis established at 36h, in 5 hr, 30 min
A day in. The body is making its own glucose, and it is practised at it.
Fast ended. Undo puts it back as it was, for two minutes.
Puts the fast back as it was, still runningRefeed
Ease back in over the next two days. Start small and light, something like broth, yoghurt or cooked vegetables, then a modest meal a few hours later. Keep drinking water and go gently. Follow the graded refeed and electrolyte checks your clinician planned.
Logged at 09:41
Logs a refeed meal nowBetween fasts
Start when your last meal ends. Every stage shows what research measured in healthy adults, not a reading of your body.
48-hour fast
48h, 2-day refeed
Ends Fri 09:41 · you choose when to end
Timer
Style
The Live Activity and widgets keep the ring.
Count
Elapsed counts up from the start; Remaining counts down to the planned end.
End this fast
Stillness is not idleness. A great deal is being sorted out.You kept the plan. Log it as it was, then go and eat.
Ending early on purpose still counts as a kept plan when you say why.
How do you feel? · optional
Stop and seek help if
- Fainting, near-fainting, or persistent dizziness on standing
- Palpitations or an irregular heartbeat
- Confusion, severe headache, muscle cramps or weakness
- Persistent vomiting or diarrhoea
- Blood glucose below 4 mmol/L if you take insulin or sulfonylureas
- Severe joint pain or swelling
- Chest pain, breathlessness, or symptoms of ketoacidosis if you have diabetes
In an emergency call 999.
In the app, a button here calls 999. This page cannot place a call: dial it yourself.
Reading this card is not logged or assessed; it is the same for everyone. Ending from here records the fast as ended because you felt unwell.
Now
Glycogen largely spent
Most of the liver's stored sugar has been used.
What to do: Two to three litres of fluid a day to thirst, with sodium. Sleep early.
Next: Ketosis established at 36h, in 5 hr, 30 min
Rothman 1991, Nilsson and Hultman 1973, Owen 1998
When did you last eat?
A 96-hour fast, only with your clinician
Published safety data for fasts over 72 hours come only from supervised settings, with electrolyte monitoring and a slow, graded refeed. Nesteia asks you to confirm these three things before each fast this long; it cannot check them, and they are recorded on this fast only.
After 96 hours, refeed over at least three days: small amounts first, building up each day, with your electrolytes checked as your clinician planned.
You reached 48 hours
The plan held. That was the whole task, and it is done.
Fast ended
30 hours 30 minutes, 48-hour fast. Logged in History.No fast running, so no Live Activity: it ends with the fast.
The Lock Screen shows the same fast: the stage, the count, a bar to your planned end and the next stage; the Dynamic Island carries a small ring. Press play and it follows.
Your timer, your way.
Ring, Dial or Minimal, with seconds on or off, chosen on the timer itself: tap it and its sheet opens. It counts up from the start or down to the planned end, and the Live Activity and the widgets keep the ring whichever style Today uses.
The planned window is the unit of everything.
Start when you last ate, end when you say so. At each stage change, in the final hour and when a plan is kept, a short reflection appears under the ring, in a calm voice that never presses you to go longer.
Daily windows
12:12 to one meal a day. The eating window is the gap at the top of the ring, and stages are tick marks on its track, never a change of hue.
Multi-day fasts
24, 36, 48 and 72‑hour plans with refeed days built in, and 96 and 120‑hour plans only under a clinician, confirmed before every such fast. Set the start to when you last ate; there is no button to extend.
Custom lengths
Twelve to seventy-two hours in one-hour steps, screened like the built-in plans and free to 36 hours. The 96 and 120‑hour plans exist only as the supervised built-ins.
Lock Screen and widgets
The Live Activity shows the stage, the count, a bar to your planned end and the next stage, with a ring in the Dynamic Island and "Not feeling right?" one tap away. Widgets: the fast ring, round or rectangular on the Lock Screen and small or medium on the Home Screen, and your last seven windows in a Rhythm widget, medium on the Home Screen or a rectangle on the Lock Screen.
Notifications you choose
Stage changes, the final hour and refeed mornings, each a switch; all scheduled on the phone, none asking you to go longer.
History and your log
Every fast on one segment of History, your log of weight, refeed meals and rest weeks on the other; Pro draws the weight trend. Fasts export as CSV, and a full JSON archive imports on another phone.
Undo and Resume
Undo restores a fast ended by mistake for two minutes; Resume, from History, picks up the most recent fast for ten minutes. There is no pause.
When a fast ends
A full-screen "Fast ended" moment says "Kept to plan" or "Logged in History" and waits for you to tap Continue. A new badge has its own unlock with one button, Done; neither appears in Quiet Mode.