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 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 2.4.7

Additional bug fixes for Watch complications not showing up for some users. Please note that Watch OS 4 and above is required to use Zero on Apple Watch.

Ratings and Reviews

4.8 out of 5
68.3K Ratings
68.3K 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.

Xootr ,

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 👍🏼


Big Sky Health, Inc.
61.5 MB
Health & Fitness
Requires iOS 10.0 or later. Compatible with iPhone, iPad, and iPod touch.
Age Rating
Rated 12+ for the following:
Infrequent/Mild Medical/Treatment Information
© 2018 Big Sky Health, Inc.


  • Family Sharing

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

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