ONE is the intermittent fasting app built to keep you on track. Set your fasting schedule, scan food in seconds, and watch real results unfold — all in one place.
Intermittent fasting is an eating pattern that alternates between defined fasting periods and eating windows. Unlike traditional diets, it focuses on when you eat — not what you eat. Your body responds to these fasting periods by lowering insulin, burning stored fat, and triggering cellular repair through a process known as autophagy.
The practice aligns naturally with your circadian rhythm. When you extend the overnight fast by a few hours, your body shifts from glucose burning to fat burning. Studies show this metabolic switch can support weight loss, improve insulin sensitivity, and reduce markers of inflammation — without requiring a complicated meal plan.
Time-restricted eating is one of the most researched forms of intermittent fasting for beginners and experienced practitioners alike. Whether you choose 16/8, 18/6, or 20/4, the core principle is the same: give your digestive system a real break, and let your body do what it was designed to do.
What happens during your fast
Fed State
Hours 0–4 · Digestion & glucose use
Fasting Begins
Hours 4–8 · Insulin drops
Fat Burning
Hours 8–16 · Ketones activated
Autophagy
Hours 16–24 · Cellular repair
From setup to first fast to long-term results — here is exactly how ONE works.
Choose your fasting schedule in under 60 seconds. Pick a protocol — 16:8, 18:6, 20:4, or custom — set your daily fasting goal in hours, and configure your weekly plan day by day. ONE auto-cycles between your fasting window and eating window so you never have to think about when to start. It just runs.
What you configure
One tap. That's all it takes to begin. A live circular progress ring counts every minute of your fast and automatically tracks which of the 5 metabolic phases your body is in — in real time.
You get a push notification every time you cross into a new phase, with tips and guidance tailored to exactly where you are in your fast.
The 5 fasting phases ONE tracks
Body using energy from last meal, insulin high
Stored carbs becoming fuel, insulin falling
Fat oxidation increasing, insulin low
Ketones becoming major fuel, insulin very low
Cellular repair activity likely elevated
After your fast, ONE keeps working. Scan food barcodes to log your meals, track water intake, log your weight, and review your fasting history. The AI Coach analyzes your weekly and monthly data and scores your consistency — surfacing real insights like your strongest days, areas to improve, and personalized tips. Build a daily streak. Join challenges with the community. Every fast makes the next one easier.
What you track
Decades of research support intermittent fasting as one of the most effective dietary strategies for sustainable weight management and overall health.
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A 2020 review in Obesity Reviews found that intermittent fasting produces weight loss comparable to continuous caloric restriction — while better preserving lean muscle mass. When you combine a fasting schedule with adequate protein during your eating window, your body preferentially burns fat rather than muscle. Most ONE users report losing 1–2 lbs per week in their first month.
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Extended fasting periods give your pancreas a rest and help reduce insulin resistance — a key driver of type 2 diabetes and weight gain. Studies show fasting can lower fasting blood sugar by 3–6% and fasting insulin by 20–31%. Better insulin sensitivity means your cells respond more efficiently to glucose, making healthy weight maintenance easier long term.
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Many people who follow an intermittent fasting schedule report improved mental clarity during their fasting hours. When your body runs on ketones — the fuel produced during fat breakdown — your brain often performs better than on a glucose-heavy diet. Research on time-restricted eating suggests it may support BDNF, a protein linked to learning and memory.
04 / 05
Chronic inflammation underlies most modern diseases. Intermittent fasting has been shown to reduce key inflammatory markers including C-reactive protein (CRP) and interleukin-6. In parallel, studies demonstrate improvements in cholesterol profiles, blood pressure, and triglyceride levels — critical cardiovascular health indicators that go well beyond simple weight loss.
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Traditional diets require counting every calorie for every meal, all day long. An intermittent fasting schedule simplifies this dramatically — you only manage what happens within your eating window. Over time, many practitioners find that intermittent fasting for beginners becomes second nature, requiring far less willpower than conventional dieting approaches.
ONE is built around how intermittent fasting actually works — giving you the tools to track, learn, and stay consistent without the complexity.
Live countdown with built-in 16/8, 18/6, and 20/4 protocols. Gentle notifications open and close your eating window automatically.
See exactly which phase your body is in — fed state, early fasting, fat burning, or autophagy — in real time throughout your fast.
Point your camera at any food label for instant calorie, macro, and micronutrient data. Logging a meal takes under 10 seconds.
Staying hydrated during your fasting window is critical. ONE tracks daily water intake and sends timely reminders so you never confuse thirst with hunger.
Track weight trends, fasting streaks, total hours fasted, and nutrition history — all in one dashboard that keeps you motivated through the early weeks.
Connect ONE with Apple Health or Google Fit. Steps, sleep, and heart rate data give you the complete picture — not just your fasting window.
Thousands of people use ONE to stay consistent and achieve real, lasting results.
"I tried every diet before this. Intermittent fasting with ONE was the first approach that actually fit my schedule. The fasting timer kept me honest, and I stopped obsessing over food. Down 18 lbs in 10 weeks."
"As a weightlifter, I worried intermittent fasting would hurt my performance. It did the opposite. The macro tracker helped me nail my protein targets, and my body composition improved significantly in six weeks."
"I'm a working mum with zero time for complicated meal plans. ONE's food scanner and fasting timer mean I spend less time thinking about food. I've lost 12 lbs and my energy levels are so much better."
Join community who track their fasting schedule with ONE. Free to download, no credit card required.
Everything you need to know before starting your intermittent fasting journey.
Intermittent fasting is an eating pattern that cycles between periods of fasting and eating. Rather than restricting what you eat, it focuses on when you eat — giving your body dedicated windows to burn stored fat, lower insulin, and support cellular repair processes.
ONE uses a live circular timer that starts the moment you tap "Begin Fast." It automatically detects which of 5 metabolic phases your body is in based on elapsed fasting hours and sends you a push notification each time you enter a new phase — so you always know what's happening inside your body.
ONE supports 16:8, 18:6, 20:4, and fully custom fasting durations. You can also set a weekly plan with different fasting windows on different days, and the auto-cycling timer handles the transitions between your fasting and eating windows automatically.
The app tracks 5 phases: Digesting (0–4h), Glycogen Burning (4–12h), Fat Burning (12–18h), Deep Fat Burn / Ketosis (18–24h), and Extended Fast (24–36h). Each phase reflects a real metabolic shift — knowing which phase you're in helps you understand why you feel a certain way and what your body needs at that exact moment.
Yes. ONE has a built-in barcode food scanner. Point your camera at any packaged food, confirm the portion size, and the nutritional data is logged instantly. You can also search foods manually, review your food log, and see nutrition stats — all without leaving the app.
Yes. On iOS, ONE syncs with Apple Health to read activity data and write nutrition logs. On Android, it integrates with Health Connect. This means your fasting data and food scans can live alongside the rest of your health data in one place.
Yes. The AI Coach analyzes your fasting sessions weekly and monthly and gives you a score from 0–100 based on consistency. It surfaces categorized insights — achievements, strengths, areas to improve, tips, and warnings — so you get a personalized action plan, not just raw numbers.
Intermittent fasting is well-studied and considered safe for most healthy adults. ONE is a tracking and habit-building tool — it does not provide medical advice. Always consult your doctor before starting any fasting protocol, especially if you have a medical condition, are pregnant, or take medication.
Every day you complete a fast, your streak grows by one. Miss a day and it resets — so streaks keep you accountable without being complicated. Challenges are multi-day fasting goals you join from the Explore tab. Your progress is tracked as a percentage and visible from the home screen.
ONE is free to download with core fasting timer and tracking features included. A premium subscription unlocks advanced analytics, the AI Coach, extended phase tracking, and more. You can start your first fast for free without signing up.
Download ONE — free to use, no credit card required. Available on iOS & Android. Visit www.fastingtime.co/
Expert guides on fasting schedules, meal planning, and maximising your results.
Beginner Guide
Schedule Comparison
Nutrition