Downloaded and used by millions of fasters!

Zero is a beautifully designed tracker used for intermittent, circadian rhythm, and custom extended fasting. As the largest app-based fasting community in the world, Zero makes it simple for anyone to harness the power of fasting to improve their health.

For most of human history, we’ve lived through feasts and famines, and the human body evolved to benefit from periods of time without eating and digesting food. Zero helps you return to this way of living.

Zero’s advisory team includes some of the world’s leading doctors and researchers, including our Chief Medical Officer Dr. Peter Attia, who guides our fasting protocols and content creation.

Zero makes fasting simple:

• A beautiful, thoughtful design makes it simple to start fasting

• Earn badges to celebrate your fasting milestones and stay motivated

• Log your weight and set a weight goal

• Detailed tracking features to visualize your progress

• Post-fast journaling to reflect on your experience

• 16-Hour (16:8) Intermittent Fast - Popularized by Hugh Jackman and Dwayne “The Rock” Johnson when preparing for blockbuster films

• Circadian Rhythm Fasting - Based on the research of Dr. Satchin Panda (Salk Institute), this 13 hour fast starts at or before sunset. Zero automatically calculates the daily sunset time based on your location

• Popular fasts - 18:6, 20:4, 36-Hour fasts and custom fasting up to 7 days long

• Choose your favorite protocol and Zero will track your ongoing progress on your iPhone or Apple Watch with Apple Health integration to sync your weight data

• Based on science from leading researchers and doctors, including Zero Chief Medical Officer Dr. Peter Attia

Fasting made simple. Join the largest fasting community in the world!

What’s New

Version 3.3.0

Hi Zero crew,

How are you feeling?

Today’s release is all about awareness of your body during your fasts. We’re updating the Fast Journal, so you can add notes about how you’re feeling at any point during your fast, instead of waiting until the end. You’ll also be able to see how your mood changed throughout your fast on a nifty chart.

To add an entry, start a fast and tap on the smiley face emoji in the bottom left of the timer.

We hope you love it!

Happy fasting,
Team Zero

Ratings and Reviews

4.8 out of 5
147K Ratings

147K Ratings

Stribb01 ,

Wonderful app for Intermittent Fasting (IF)

This app is truly a lifesaver! I have an unusual manifestation of Temporal Lobe Epilepsy and must stick to a low carb diet. I recently had a back surgery that went horribly wrong. I was forced to stay in bed for almost a month! I had to eat whatever was brought to me from the local restaurants and fast food joints. Prior to that, I had been on a strict KetoDiet for years! I gained 15lbs and felt terrible. After my recovery, I restarted my KetoDiet but the weight wasn’t coming off. I was also retaining water and I felt terrible. Then I learned about Intermittent Fasting (IF). Thanks to this wonderful app, I am losing 2lbs a week and I feel great! I generally do the 16 hour fast and then the 13. With the custom setting, I can do a 24 hour fast for religious reasons as I am a Christian and we are taught to fast and pray. But that’s my own personal decision. The custom Fast lets you use a slide to choose your own number of IF hours. So if your a newbie or might have issues with food, you can ease yourself into a full 13 hour or 16 hour or a longer period of IF! That’s what’s so wonderful about this app. You can also chose to count your IF hours up or down in order to keep yourself motivated.

SharkosaurusRex ,

An essential download for weight loss

I’ve tried countless diets and none of them ever felt good. I have severe anxiety and major difficulties with memory and would get torn between eating out with friends or sacrificing my diet, both options sending me into an attack. Until I found Intermittent Fasting. It’s the first time I’ve felt truly free and in full control of my eating, with the added bonus of giving me tons of energy. And there’s no way I would’ve been able to lose as much weight (20 pounds in less than two months!!) without this incredible app. It’s simple, efficient, sends beautifully easy notifications, and even has a dark mode. The app shows you how many people are fasting with you, has options for the different kinds of fasts, helpful information, and much more. If you’re even remotely curious about weight loss, control over eating, or IF at all, you need this app. It costs a whole 0 dollars, so why not give it a shot?

emac-nyc ,

Used to be 5 stars...

The previous version of this app had a much more refined UI. I gave the previous version 5-stars while I give the current version 3-stars.

This version is still functional, and it provides more information. That said, the current UI is unnecessarily busy and lacks simple but powerful elements of the previous version.

One of these elements is when a person reached their goal the whole UI would change from the red to green. While this is a seemingly simple thing, it had a powerful effect on my experience. With the current version, I no longer get the satisfaction from glancing at the app during my day following reaching my goal nor do I get the resultant motivation to keep pushing on beyond my minimum goal.

Another example is the interface for initiating my fasts. The previous version of the interface was more simple and in my experience more inviting to initiate a fast. For me, it was actually a small joy to press start on the previous version. Now I am faced with several pieces of unnecessary data surrounding the start button. It fees more like a chore than a pleasure now. There is too much noise surrounding the experience I am seeking

I really value this app, and I believe it can help people. I hope these deteriorations and others are addressed and not worsened. The first version was so much closer to nailing it

Developer Response ,

Thanks for sharing this feedback. The color change UI is something we're working to address after hearing from our users. We've also updated the flow for starting a fast, so that it's the simple one tap that you were previously a fan of. We hope you'll stick with us to check out these updates!

Happy Fasting,
Team Zero


Big Sky Health, Inc.
105.5 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

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

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