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 3.2.4

Hi, Zero crew! Just doing some quick cleanup to make sure our systems are working 100%.

Thank you for your continued feedback and support!

Happy fasting,
Team Zero

Ratings and Reviews

4.8 out of 5
128.2K Ratings

128.2K 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.

MoocowMF ,

If you are the fence...

About this app or about fasting in general, go for it.
This app is a very well designed helper with first time fasters. If you cut yourself off, and forget to start the clock, you can edit the start and stop times by tapping the corresponding number on the screen. If you forget to start the app- or that you intended to fast at all, (hello me) there is a gentle reminder shows up on your lock screen.
Overall, I started a 16/8 and feel amazing, AND I’m cutting out (yikes!) thousands of calories I’m not eating in the evening. I’ve been starting around 4p and although the app congratulates me for completing at 8am, I go for a few more hours. I’ve found I’ve lost weight, but most of all I have more energy, I don’t crash midday. Yes, at night I feel my stomach whining for food, but I know if I get thru it, I will feel great in the morning.
Try fasting, try this app.

Stromba926 ,

You guys messed up with the recent update

One of my favorite apps. I used it all the time for my fasting journal. I just got done deleting it after the new version forces you to login your personal information… Not something anyone wants! I kept declining and every time I declined it would refuse to allow me to set the timeframe in custom fasting option. If I did not allow notifications it also prevented me from doing a custom fasting option. it now tries to link you through Facebook etc. All the different options that you added cannot outweigh the fact that you’re definitely mining for more information on your customers and this is a deal breaker. I’m not going to be forced to give my information and allow notifications when I don’t want them. The old version I just entered what time I started, what time it ended and it worked fine now I have to go look for another app or some other means of tracking my progress for fasting. Whoever came up with this so Called upgrade needs to have their head examined. People do not like being forced into corners where they have to allow notifications and or give their personal information!!!!


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

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

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