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 on your iPhone or Apple Watch. Export your data to a spreadsheet for complete control.

Zero supports the following fasting types:

16-Hour (16:8) 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.

We also support 18:6, 20:4, and 36-Hour fasts.

Custom Fasting: Set up a custom program to meet your fasting goals. You choose your fasting hours, up to 7 days long.

Zero is also available on Apple Watch.

Zero integrates with the Health app to sync your weight data.

What’s New

Version 3.2.1

Hi, Zero crew! Today’s update is all about bug fixes and small tweaks, specifically:

• If you’ve been having issues with Zero not showing up as a source for Apple Health, then this update should fix that.
• We’re now showing you some of your unearned badges on the main badges screen, which you can access from the History tab.
• We’ve also made some small updates to copy in the app so things read a little clearer.

Thank you for continuing to report bugs. Keep bringing them up and we’ll keep doing our best to squash them.

Happy fasting!

Ratings and Reviews

4.8 out of 5
10.6K Ratings

10.6K Ratings

roxabelle ,

Simply genius.

I love it. It’s easy to get into, simple to use, and has seriously helped me kickstart my process of slimming down. Just 6 days in to the 16:8 method my clothes fit better than ever, and that is largely aided by having an uncomplicated app like this one to track my progress and keep me motivated. If I forget to start (or finish) recording my fasts I can easily edit them in the app. If I could add one thing I’d love to be able to switch views on the main screen, between counting the number of hours you’ve been fasting for to just showing the time you started and the time you can stop. So at a glance you can see the time itself rather than counting hours - particularly when you’re adjusting your fast period to fit with social activities (I.e. fasting usually begins at 6 pm for me, but that’s when yoga finishes one day a week, so I move it back to half 6 so I can get a light bite in after, and start later the next day). All in all a simply brilliant app, and I’ve been recommending it to everyone. So grateful that this was put together and shared for free 🙌🏻🙌🏻🙌🏻

JohnTFinlayson ,

New update makes this 5*

Freaking love this app now. Badges clearly are for chumps... But I'm admittedly one of those chumps who secretly gets motivated by them. The new graphics for timers is somehow much more motivating. Dark mode is very welcomed. Integration with Health App is major win, with the history section being a very useful integration of wieght data. All round, totally love this now. I've not used the Learn section yet due to being 10years into seasonal water fasting and well read around the benefits and need for wisdom/safe-decisions, however, having Dr Attia as point of advice is very reassuring and adds further credibility to the project behind this app. Thanks for hard work all!

MatchSnob ,

Amazing app!

I was fasting without this app for weeks! but now with the app it makes it easier! makes everything so visual, it makes everything just so easy from a person with adhd’s perspective!!

the only thing i would really love to make it just that bit better/easier would be: when you stop your fast and the non fasting timer starts it would be awesome to edit your reminder to fast again by tapping “remind me when timer reaches near 4/6/8 hours (or whatever non fasting window)” instead of having to calculate this time yourself. i know! i’m lazy! haha

love this app so much! thanks guys!


Big Sky Health, Inc.
67.2 MB
Health & Fitness

Requires iOS 11.0 or later. Compatible with iPhone, iPad and iPod touch.



Age Rating
Rated 12+ for the following:
Infrequent/Mild Medical/Treatment Information
© 2019 Big Sky Health, Inc.


  • Family Sharing

    Up to six family members will be able to use this app with Family Sharing enabled.

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