The intermittent fasting timer built for results. Track metabolic zones from fat burning to autophagy. Live on your lock screen, home screen, and Dynamic Island. No calorie counting. No meal plans. Just precision.
Download for iPhoneFree to try · No account required
Most fasting apps show a countdown. LockFast shows you the metabolic phase you're in — updated in real time as you progress through your fast.
Digesting and storing energy. Insulin elevated, body using glucose as primary fuel.
Glycogen depleting. Your body begins mobilizing fat stores for energy.
Liver producing ketone bodies. Brain and muscles switching to fat-derived fuel.
Cellular cleanup activated. Damaged proteins and organelles being recycled.
Most fasting apps disappear the moment you close them. LockFast stays with you — on your home screen, lock screen, and Dynamic Island.
See your progress ring, elapsed time, metabolic zone, water intake, and streak count — without opening the app. Glanceable data, always fresh.
Your fasting timer runs live on the lock screen and in the Dynamic Island. See elapsed time, zone, and progress without unlocking your phone.
Quick-add buttons for 250mL, 500mL, and 750mL. Daily goal with progress bar. Resets automatically at midnight. Hydration data syncs to your widget.
When your fast ends, LockFast automatically counts down your eating window. Know exactly when your next fast starts. One-tap to begin early.
LockFast does one thing exceptionally well: track your fasts with precision and clarity.
Start your fast instantly. Choose from 16:8, 18:6, 20:4, or OMAD protocols. Switch anytime.
Rolling 7, 30, and 90-day trends. Metabolic zone time breakdown. 14-day compliance charts.
Current streak, longest streak, and weekly compliance at a glance. Calendar heat map shows your consistency.
Track weight alongside your fasting data. See how consistency correlates with body composition changes.
Get alerted when you hit your target, enter a new metabolic zone, or are about to break your streak.
Built for checking at 6 AM and 10 PM. Clean, minimal, no visual clutter. Looks great on OLED screens.
The basic timer is free forever. LockFast Pro unlocks metabolic zone tracking, advanced analytics, home screen widgets, Live Activities, water tracking, eating window timer, and smart notifications.
Can't find your answer? Email us at [email protected]
Long-press your iPhone home screen until apps jiggle → tap the + button in the top corner → search "LockFast" → choose Small or Medium → tap Add Widget. The widget shows your timer, metabolic zone, water intake, and streak.
The Live Activity starts automatically when you begin a fast. It appears on your lock screen and in the Dynamic Island (iPhone 14 Pro and later). No setup needed — just start a fast.
On the home screen, tap any of the quick-add buttons (250mL, 500mL, or 750mL) to log water. Your daily total resets at midnight. You can change your daily goal in Settings. Water intake also appears in the medium widget.
When you end a fast, LockFast automatically starts a countdown for your eating window based on your protocol. For example, on 16:8, you get an 8-hour eating window countdown. You can start your next fast early with one tap.
Open your iPhone Settings → tap your name at the top → Subscriptions → find LockFast → Cancel Subscription. Apple manages all billing — we cannot cancel subscriptions on your behalf.
Open LockFast → Settings → Subscription → Restore Purchases. Make sure you're signed in with the same Apple ID you used to subscribe.
The metabolic zone indicators are estimates based on published research averages. Individual timing varies based on age, body composition, activity level, diet, and metabolic health. They are not medical measurements.
Open LockFast → Settings → Apple Health → toggle it on. LockFast can read your weight data and write fasting session information to Apple Health.
Apple handles all refunds directly. Visit reportaproblem.apple.com, sign in with your Apple ID, find the LockFast charge, and request a refund.
Open LockFast → Settings → scroll to the bottom → Reset All Data. This permanently deletes all fasting sessions, streaks, and preferences from your device.
Last updated: March 2026
LockFast ("we," "our," or "us") respects your privacy. This Privacy Policy explains how we collect, use, and protect your information when you use the LockFast mobile application (the "App").
Information You Provide:
Information from Apple Health: If you grant permission, LockFast may read weight data from Apple Health and write fasting session data to Apple Health. This data transfer occurs only on your device and is not sent to our servers.
Subscription Information: If you subscribe to LockFast Pro, Apple processes your payment. We receive confirmation of your subscription status but do not receive or store your payment details.
Analytics Data: We may collect anonymized, aggregated usage analytics to improve the App. This data cannot be used to identify you personally.
All your fasting data is stored locally on your device. We do not operate servers that store your personal fasting data.
We do not sell, rent, or share your personal information with third parties. We do not display advertisements. Our revenue comes exclusively from subscriptions.
LockFast is not intended for use by children under 13. We do not knowingly collect information from children under 13.
We may update this Privacy Policy from time to time. We will notify you of material changes by updating the "Last updated" date above.
Email: [email protected]
Last updated: March 2026
By downloading, installing, or using the App, you agree to be bound by these Terms. If you do not agree, do not use the App.
LockFast is a fasting timer and tracking application that allows you to track intermittent fasting sessions, monitor estimated metabolic zones, view fasting history and statistics, set fasting reminders, and optionally sync with Apple Health.
Free Tier: LockFast offers basic fasting timer functionality at no cost.
LockFast Pro is available as an auto-renewable subscription:
Payment is charged to your Apple ID account at confirmation of purchase. Your subscription automatically renews unless canceled at least 24 hours before the end of the current period. You can manage or cancel your subscription at any time through your Apple ID account settings (Settings → Apple ID → Subscriptions).
Free trial periods automatically convert to paid subscriptions unless canceled before the trial ends.
LockFast is designed for informational and tracking purposes only. The App is NOT a medical device and does NOT provide medical advice.
The metabolic zone indicators (Fed, Fat Burning, Ketosis, Autophagy) are estimates based on published research averages and may not reflect your individual metabolic state.
Consult a qualified healthcare professional before starting any fasting regimen, especially if you have diabetes, are pregnant or nursing, have a history of eating disorders, are under 18, or take medications affected by food intake.
You agree to use the App only for its intended purpose, not attempt to reverse-engineer or modify the App, and not use the App in any way that violates applicable laws.
The App, including its design, code, content, and branding, is owned by LockFast and protected by copyright and intellectual property laws. You are granted a limited, non-exclusive, non-transferable license to use the App for personal, non-commercial purposes.
To the maximum extent permitted by law, LockFast shall not be liable for any indirect, incidental, special, consequential, or punitive damages arising from your use of the App. Our total liability shall not exceed the amount you paid for the App in the twelve months preceding the claim.
The App is provided "as is" and "as available" without warranties of any kind, either express or implied.
These Terms shall be governed by the laws of the State of Colorado, United States.
Email: [email protected]
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