Safety
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 exist for people fasting under a clinician, confirmed before every such fast, and nothing passes the 120‑hour ceiling. These rails live in the timer, not in a terms page. Tap a rail for its rule.
- Adults only. Nesteia opens with an age gate, before the timer. Its App Store age rating is 18+.
Rule: the age gate sits in onboarding, and the timer does not open until you confirm you are 18 or over.
- Screening on plans over 16 hours. Three questions about eating history. A yes turns on Gentle Mode and shows Beat and NEDA resources once. It never blocks the app.
Rule: any plan longer than 16 hours asks three questions first; a yes turns on Gentle Mode and shows Beat and NEDA once.
- Acknowledgement at 48 hours. A one-time risk acknowledgement and confirmation of no contraindications; refeed days are built into the plan.
Rule: the first plan of 48 hours or more asks for one acknowledgement and a confirmation of no contraindications; a refeed card follows the fast.
- Supervision confirmed before every plan longer than 72 hours. The 96 and 120‑hour plans ask three things before each start: a clinician is supervising this fast, electrolytes are being monitored, and a graded refeed of at least three days is planned. The answers are recorded on the fast.
Rule: a plan over 72 hours starts only after all three statements are confirmed, every time, on top of screening and the 48‑hour acknowledgement; the confirmation is stored with that fast.
- The ceiling, everywhere. Timer, plan picker, custom lengths, start-time edits, CSV import, deep links, the Live Activity and widgets. A running fast ends itself at 120 h.
Rule: no timer, plan, custom length, start-time edit, import, link or widget can pass 120:00:00; a running fast ends itself there and the ring stops full. Plans longer than 72 hours cannot be started without the supervision confirmation; a fast already running is not stopped at its goal, it runs on until you end it or the ceiling does.
- Spacing between long fasts. No two fasts of 48 hours or more within 14 days, measured from the end of one to the start of the next; the app will not start the second.
Rule: after a fast of 48 hours or more, the next one of that length cannot start for 14 days.
- Longer spacing after a supervised fast. After a fast that ran over 72 hours, the next one over 72 cannot start for at least 28 days; your clinician may advise a longer gap.
Rule: the app measures from the end of a fast over 72 hours and will not start another over 72 for at least 28 days. The 14‑day rule still applies to everything of 48 hours or more.
Stop signs
On any fast over 24 hours, a "Not feeling right?" link sits under the ring and on the Lock Screen. It opens the stop card, with your region's emergency number one tap away. End the fast and seek help if you notice any of these:
- 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
Ending from the stop card is logged without judgement and never followed by an upgrade offer. The stage cards say what to do as you go: a sodium source from 18 h, two to three litres of fluid a day to thirst from 24 h, stand up slowly from 36 h; past 72 h they defer to the clinician supervising you. Nesteia does not monitor, diagnose or treat any condition and is not a substitute for your GP.
Six things the timer does quietly
Built into the app, not a settings maze. Each one is here to keep a fast calm, never to push it longer.
- Ending
- A fast ends when you say so; the plan’s end is a notification, not a stop. You give a reason and how you feel, one to five, and ending early on purpose is a kept plan. A calm “Fast ended” moment waits for your tap. Ended by mistake? Undo restores it for two minutes, Resume in History for ten. There is no pause.
- Reflections
- A short line under the ring at each stage change, in the final hour and when a plan is kept. Calm, in the app’s own words, and never a push to go longer. Off in Settings if you prefer.
- Notifications
- Stage changes, the final hour and, after a fast of a day or more, a note at 9:00 each refeed morning, each on or off in Settings; the note at your planned end always arrives. In your quiet hours they come silently and wait in Notification Centre. All are scheduled on the phone; none nudges you to fast longer.
- Lock Screen
- The Live Activity shows the stage, the count, a bar to your planned end and the next stage; the Dynamic Island carries a small ring. Widgets for the Home and Lock Screens show the ring, or the last seven daily windows of your rhythm strip. They follow whichever timer style you use, and none counts past 120 hours.
- Gentle Mode
- Hides hour counts past 16 h and shows “window kept” instead, and hides the layers of 36 h and above. Turns on after any screening yes; you can switch it in Settings.
- Quiet Mode
- The ring, the stage and two actions. Nothing else: no reflections, no “Fast ended” moment, no unlock.
Privacy
Your fasting history stays on your phone.
- On device by default. No account, no server. We never see a fast.
- iCloud sync is yours to switch on. A Pro setting, off by default. When it is on, your fasts, weight entries, refeed meals, rest weeks and badges are stored in your own private iCloud database under your Apple Account; your screening answers and settings stay on the phone, and still nothing reaches us.
- No analytics, no SDKs. The only third party is Apple, for App Store purchases and, if you turn it on, iCloud.
- Export and delete. CSV of your fasts, or a full JSON archive of everything the app holds, out at any time and importable on another phone; "Delete everything" removes it all in one step, including the iCloud copy when the app was opened with sync on. Privacy policy.
Nesteia is in testing on iPhone and not yet on the App Store.
Free: every daily window, and plans and stages to 36 h. Pro from £4.99 a month at launch.