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Zero is a simple fasting tracker used for intermittent, circadian rhythm, and custom fasting. Choose your favorite fasting protocol and Zero will track your ongoing progress. Export your data to a spreadsheet for complete control.

Zero supports the following fasting types:

16-Hour Intermittent Fast: Popularized by Hugh Jackman and Dwayne “The Rock” Johnson as a fast to trim extra pounds. It is common to fast after dinner to around lunch the following day.

Circadian Rhythm Fasting: Based on the research from Dr. Panda (Salk Institute), participants are encourage to fast 13 hours per day, starting each fast at or before sunset. Zero uses your location to calculate the daily sunset time for the best possible accuracy.

Custom Fasting: Setup a custom program to meet your fasting goals. You choose your fasting hours per day, and days per week.

What's New

Version 2.2.0

- Start fast reminder: You can now set a daily "start fast" reminder.
- Toggle time display: Tap the time to switch between Elapsed Time and Remaining Time.
- Misc bug fixes.

Ratings and Reviews

4.8 out of 5

42.4K Ratings

42.4K Ratings

Great for Intermittent Fasting


I follow a keto diet and lifestyle and eat in an 8 hour window. Zero helps me track my 16 hour fasts. You can create a custom fast time period and then press Begin Fast when you’re done eating for the day. When you meet your goal, an alert pops up to let you know you have been successful. I am VERY grateful for this alert because I would probably forget to eat otherwise. My appetite has really diminished on keto, and since I’m a First Responder, I can’t risk rushing off to a emergency and suddenly realizing I’m famished and haven’t eaten in 20 hours (it’s happened and it SUCKZ). Zero helps me remember that I’ve given my body a rest from digestion and it’s time to refuel for the day’s adventures. I simply get my meal 🥓🥦🍳🥑☕️, press End Fast, and chow down. After dinner I just repeat the same steps.
So simple and so effective 👍🏼

Simple fasting app with clean interface


I’ve enjoyed using this app over the past three weeks, though I’ve been fasting intermittently alongside keto since August with my wife. The interface is simple and doesn’t get in the way of what I want to do. The export feature is easy to use.

The lastest update includes a disclaimer, which is a professional move by the publisher. Please read it carefully. Don’t attempt the 16-hour fasts without careful study and speaking with a health care professional. Much of the science behind fasting is positive, but certain conditions may complicate.

My one recommendation on improvement would be to add a widget for quick glances at fasting progress rather than being forced to jump in and out of the full app. Perhaps this could be a feature requiring payment.

Pretty good but....


I like that I can start fasting and just keep the clock going (as I am doing extended fasting) but no matter how far I go, it’s not counting the days. I started a 96 hr fast last Saturday and when I broke it to eat, it showed all of the hours under Saturday. Like....why? It’s covering days, why not show that my goal is 24 hours and I completed x many days? If they can fix that, I will change this to 5 stars. I haven’t found any other free apps that will allow me to have an open clock on fasting and track it for me...so I do really like the premise for the app. I just wish it tracked the days as well as the hours. At first glance it looks like I did a long day Saturday and then ate until my next fast started on Wednesday- when I was fasting the whole time and only broke it to eat something in a 5 minute timeframe.


Big Sky Health, Inc.
57.4 MB
Health & Fitness
Requires iOS 10.0 or later. Compatible with iPhone, iPad, and iPod touch.
Age Rating
Rated 4+
© 2017 Courtney Circle


  • Family Sharing

    With Family Sharing set up, up to six family members can use this app.

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