Nesteia

A fasting timer that tells you the truth about what is happening in your body.

Daily windows and multi-day water fasts to a 120‑hour ceiling; anything over 72 hours only with a clinician's supervision, confirmed for every such fast. Eleven measured body stages with their human evidence. A history that never leaves your phone.

Coming to theApp Store iPhone, iOS 26 or later. Free timer, plans and stages to 36 h. 18+.
09:41100%
Day 2 of 2 · 48‑hour fast
of 48 h
next stage in 5 h 30 m
Glycogen largely spent

Most of what happens now happens quietly.

Not feeling right?
End fast

Try the ring; tap the numeral to flip the count. Nothing in it can pass 120 hours, and the 96 and 120‑hour plans run only with a clinician's supervision.

Nesteia · Live Activity 30:30:00 Glycogen largely spent · of 48 h

The Lock Screen shows the same fast as the ring, and keeps the ring whichever style Today uses. Press play and it follows.

Timer styles

Your timer, your way.

Ring, Dial or Minimal, chosen in Settings ▸ Fasting, with seconds on or off. Tap the numeral to switch between time elapsed and time left; the Live Activity and the widgets keep the ring whatever you choose.

RingThe full circle, the tide arc filling it from the top, a tick at each stage boundary inside the plan.
DialA 270° gauge open at the bottom, a sixty-division tick scale, the start and the plan's length at its two ends.
MinimalThe numerals alone over a two-point progress line, the stage's name beneath.
How it works

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.

16:8

Daily windows

12:12 to one meal a day. The eating window is the gap at the top of the ring; the fast is the arc, and stages are tick marks on its track, never a change of hue.

120 h

Multi-day fasts

24, 36, 48 and 72‑hour plans with refeed days built in, and 96 and 120‑hour plans for people fasting under a clinician, confirmed before every such fast. Set the start time to when you last ate. No button to extend.

12–72

Custom lengths

A Custom row in the plan picker, twelve to seventy-two hours in one-hour steps, with the same screening and acknowledgement as the built-in plans. Free to 36 hours; the 96 and 120‑hour plans exist only as the supervised built-ins.

Lock Screen and widgets

Elapsed time and current stage in a Live Activity and the Dynamic Island, and as widgets: a circle or a rectangle on the Lock Screen, and the small and medium sizes on the Home Screen. "Not feeling right?" is one tap from the Lock Screen.

Notifications you choose

Stage changes, the final hour of a plan and, after an extended fast of a day or more, a note at 9:00 on each refeed morning, each on or off in Settings; the note at your planned end always arrives. In your quiet hours a note arrives without a sound or a lit screen and waits in Notification Centre. All of them are scheduled on the phone, and nothing ever nudges you to fast for longer.

History and your log

The History tab holds every fast on one segment and your log on the other: weight, refeed meals and rest weeks, entered there and nowhere else, free. Pro draws the weight trend. Fasts export as CSV for a spreadsheet; everything the app holds exports as a full JSON archive that imports on another phone.

2 m

Undo and Resume

Ended by mistake? Undo, for two minutes after the end, restores the fast exactly as it was. Resume, from History, picks up the most recent fast for ten minutes after it ended. There is no pause.

When a fast ends

A full-screen "Fast ended" moment: the ring sweeps to where the fast got, the count settles, and one line says "Kept to plan" or "Logged in History". It waits there until you tap Continue, or anywhere on the screen — nothing is read to a clock. A new badge has its own full-screen unlock, the disc materialising on paper tinted in its family's tone, with one button, Done. Neither appears in Quiet Mode.

Body stages

Eleven stages, measured in people, each with its confidence.

What studies measured in healthy adults, not a reading of your own body. The first five of the six free stages, to 36 hours:

  1. Your last meal is still being absorbed. Insulin is high and the liver stores glycogen.

    Free

  2. Insulin is back at baseline. The liver releases stored sugar and begins making new glucose from other sources.

    Free

  3. Fat is released from stores in larger amounts. Ketones are usually still near baseline.

    Free

  4. Blood ketones pass 0.5 mmol/L at a mean of 21 hours, SD 3 hours. Timing varies from person to person.

    Free

  5. Most of the liver's stored sugar has been used. The body now makes almost all its glucose fresh.

    Free

Explore all eleven stagesHour explorer, filters, the Pro stages to 72 h and the two supervised stages beyond.

Strata

Mineral badges for keeping a plan. Nothing is earned by going longer.

Earned by ending a planned fast within two hours of its target, and not more than fifteen minutes early. Same disc, same number; only the material changes.

Earned the first time you keep a plan at this layer.

Clay

Matte. The first kept plan.

Earned on the third kept plan at the same layer.

Stone

Satin, brushed. The third.

Earned on the tenth kept plan at the same layer.

Glass

Refraction. The tenth.

See the ten layersThe card for your next layer at the top, five families for keeping plans and taking care, and the rhythm strip that stands in for a counter.

Safety & privacy

The ceiling is a feature.

Published safety data for unsupervised fasting stop at about 72 hours, so every unsupervised plan in Nesteia does too. The 96 and 120‑hour plans run only for people fasting under a clinician, confirmed before every such fast, and nothing passes the 120‑hour ceiling. Seven rails live in the timer, and your history stays on your phone.

Read the seven railsEach with its rule, plus the stop signs and the privacy facts.

Pricing

The timer, and the plans and stages to 36 hours, are free, for good.

Free

£0
No account. No trial to remember.

Timer for every daily window, the 24 and 36‑hour plans, custom lengths to 36 hours, body stages to 36 hours, Live Activity, widgets, the History tab with its log of weight, refeed meals and rest weeks, CSV and JSON archive export and the First family of badges.

Pro

14‑day trial on the annual plan
£39.99a year
Or £4.99 a month, or £99.99 once for lifetime access.

48 and 72‑hour plans with refeed days built in, the supervised 96 and 120‑hour plans, custom lengths beyond 36 hours, body stages beyond 36 hours with their evidence and what to do, every Strata layer and family beyond the First family, weight trends and optional iCloud sync.

Compare the plansSide by side, cost per week, and plain answers to ten questions.