Intermittent fasting tracker and timer, built into your food log

Intermittent fasting means eating within a set window each day and fasting for the rest. An intermittent fasting tracker keeps the clock for you, but the clock is only half the story, because what you eat inside your window still counts. Calorix puts a fasting timer right next to your food log, so one fasting app shows both when you ate and what you ate.

Fasting schedules you can track

12:12 is the gentlest place to start, since most of the fast happens while you sleep. If you’re looking for a 16:8 fasting app, our 16:8 guide covers that schedule in detail, and the free intermittent fasting calculator maps any schedule onto your day.

How the fasting timer works

1. Pick a schedule from the list, or set a custom one.
2. Start your fast with a tap, or ask Siri, run a Shortcut or press the Action button.
3. Follow along without opening the app. A Live Activity shows your fast on the Lock Screen, and a fasting widget sits on your Home Screen. The timer moves through phases as your fast goes on.
4. Get reminders when it’s time to start and when your eating window opens.
5. Stop the timer when you eat. Each fast is saved to your history, so you can look back over your week.

While you fast, Toasty is asleep. It isn’t hungry or upset, just napping, and it wakes up when you log your first meal. Ending a fast early is fine: stop the timer, log what you eat, and Toasty is happy to see you. If you like having a goal, optional fasting challenges earn coins for Toasty’s outfits.

Fasting and food logging in one app

• Make your eating window count. Log meals the usual way, by photo, barcode, label, voice or text. A shorter window leaves fewer hours for meals, so it helps to plan your protein across them with the protein tracker.
• Drink while you fast. Water, sparkling water, black coffee and unsweetened tea are generally fine during a fast, while anything with calories breaks it (Cleveland Clinic). Log water in one tap from the dashboard or the water widget.
• See everything together. Your fasting history sits alongside your food log, your weekly recap and your weight trend.

Tips for your first weeks

• Start small. If 12:12 feels easy after a week or two, step up to 14:10 before trying 16:8. There’s no prize for the longest fast.
• Fit the window to your life. If you share dinner with family or friends, end your window after it and let the fast run overnight.
• Let the reminders watch the clock so you don’t have to, and glance at the Live Activity when you’re curious.
• Eat enough in your window. If you’re genuinely hungry, a Cleveland Clinic dietitian suggests adding more protein and fiber to your day. The macro tracker shows both at a glance.
• Expect off days. Travel, celebrations and sick days happen. Stop the fast, log your meals, and pick it up again tomorrow.

What the research says

Fasting is a way to structure your eating, not a shortcut. A 2025 review in The BMJ pooled 99 randomized trials involving 6,582 adults. Every fasting approach, and ordinary calorie restriction, reduced body weight compared with unrestricted eating, and the authors found some indication that intermittent fasting has similar benefits to continuous calorie restriction. Alternate-day fasting showed a small extra benefit in shorter trials, and the authors called for longer studies.

The practical takeaway: choose the approach you can keep up. If that’s 16:8, Calorix keeps time. If you’d rather not fast at all, the calorie counter for weight loss works on its own.

Who should skip fasting or check with a doctor first

Fasting isn’t for everyone. Based on guidance from Cleveland Clinic and an earlier Cleveland Clinic article, skip it, or only try it with your doctor’s guidance, if you:

• are pregnant or breastfeeding
• are under 18
• have a history of an eating disorder, since restriction can make binge eating more likely for some people
• have type 1 diabetes, low blood sugar (hypoglycemia), or another chronic condition
• are malnourished

If you have diabetes and take medication, fasting needs your care team’s supervision and careful glucose monitoring (Grajower and Horne, 2019). If you take a GLP-1 medication, ask your prescriber before you start.

Fasting can also come with irritability, low energy and persistent hunger. If it leaves you feeling unwell, stop and talk to a healthcare professional. Calorix offers general wellness information and isn’t a medical device.

Updated October 9, 2026