Why do fasting timers break when the app is closed?

Because they count with a JavaScript interval, which stops when the app is suspended. Store the start timestamp and derive elapsed time from the current clock on every render. Ask the AI for exactly that — it is the difference between an app that works and one that resets overnight.

Do I need medical disclaimers?

Yes. Fasting apps sit in the health category, so include a clear "not medical advice" notice and avoid claims about disease, weight loss amounts, or outcomes. Apple reviews health claims carefully and vague marketing copy is a common rejection reason.

How to Build a Fasting Tracker App with AI (2026)

What a intermittent fasting tracker app needs

Live fast timer with a progress ring and stage labels
Presets: 16:8, 18:6, 20:4, OMAD, custom
Streak counting and weekly completion rate
Fast history with duration and how it felt
Optional weight log with a trend line

The screens

Screen	What it does
Timer	Start/end a fast, elapsed ring, current stage, target time
Presets	Pick or edit a fasting schedule
History	Past fasts, durations, and streak calendar
Progress	Weekly completion rate and weight trend
Settings	Reminders for fast start and end, units, subscription

The data model

Fast: startAt, endAt, targetHours, presetName, mood
Preset: name, fastHours, eatHours
WeightEntry: date, weightKg
User: email, subscriptionTier

The build prompt (copy this)

Paste this into ShipNative and it becomes a working React Native app with these screens, navigable in a live preview, in about two minutes:

“An intermittent fasting tracker. Users start a fast, see a live progress ring with elapsed and remaining time, and end it when done. Presets for 16:8, 18:6, 20:4, and OMAD plus a custom option. Track streaks and weekly completion. Optional weight log with a trend chart. Screens: Timer, Presets, History with a streak calendar, Progress, Settings. The timer must compute elapsed time from a stored start timestamp so it stays correct after the app is closed or the phone restarts. Notifications when a fast is due to end. Works offline.”

Then iterate with small, screen-specific prompts (“make the primary button bigger”, “add an empty state”), preview on your own phone, and export the full Expo project whenever you want. The full method: how to build an app with AI.

How it makes money

Freemium: the timer and current streak free, full history, weight trends, and custom schedules behind a $4–8/mo subscription. Health-habit apps see the strongest conversion at the moment a user completes their first week — put the upgrade prompt there, not on install.

Implementation and the revenue math for every model: how to make money from an app. When you’re ready to ship: App Store and Google Play publishing guides.

Build it now

The prompt above is free to run at shipnative.dev — working intermittent fasting tracker app on your phone today, full code export, no credit card.

How to Build a Fasting Tracker App with AI