Fasting is simple — until it’s not. Even though the premise of not eating for a set number of hours a day sounds straightforward, getting into the nitty gritty of things can quickly send you down a rabbit hole of boundless information. We’re here to break it down, answer commonly-asked questions, and make fasting as accessible for you as possible.

Keep reading for the science-backed details on intermittent fasting!

What Is Intermittent Fasting?

Intermittent fasting (IF for short) is a pattern of eating that cycles between periods of eating and not eating. If you’re thinking that sounds oddly similar to what we do daily, you’d be correct! What separates our “normal” eating patterns from IF comes down to intentionality. When used correctly, intermittent fasting can be a powerful tool for your overall health and longevity.

IF is fantastic for anyone who’s looking to lose weight and keep it off for good. Intermittent fasting works because it’s not a diet, which makes it a feasible habit for nearly everyone. And since we all fast for (give or take) eight hours every night, extending that into a 12 or even 16-hour fast is a natural, sustainable way to ease into a healthier lifestyle.

Can Intermittent Fasting Help Me Lose Weight?

Yes! Fasting alters the frequency of your eating, which can spontaneously reduce caloric intake. It also promotes mindfulness, thus encouraging healthier, more conscientious choices around what and when you eat. Lastly, fasting enables your body to tap into its fat stores — instead of your recently-digested meal — for fuel.

How Do I Get Started?

Starting your fasting practice is easy, but the jargon that comes with it might be a little tricky to navigate at first.

Here are some must-know terms for beginners:

Fasting is convenient because you can work around your lifestyle by choosing the length of your fast as well as when and how you do it. You can skip breakfast, skip dinner, go for a longer fast at the beginning of the week, squeeze in shorter fasts throughout the week — it’s completely flexible.

How Long Should I Fast For?

If intermittent fasting is brand new to you, a 12 or 13-hour fast is a great jumping-off point. Remember, sleeping counts towards your fasting goal, so even eliminating late-night snacking or delaying breakfast can help you make great strides towards a longer fast.

For those who are a little more advanced, the 16:8 fast is the next step up and the most popular fast type for Zero Members. Longer fasts unlock some additional benefits such as accelerated fat loss, protection against inflammation, and increased longevity.

How Often Should I Fast?

For beginners, we recommend fasting for 3–4 times a week. Try to stay consistent for a least a couple of weeks before checking your weight, and remember that weight can fluctuate on a daily basis. The important thing is how you feel, and when you’re making positive lifestyle changes, the weight loss will come along for the ride.

How Can I Track My Fasts Using Zero?

Zero can help you track your fasts with the Fasting Timer, located in the Today tab. After finishing your last meal of the day, start the Timer to begin counting down towards the completion of your fast. Along the way, you’ll receive custom Fasting Tips that adjust to your gender, mood logs, and more. By tapping on the center of the Timer, you can access Personalized Fasting Zones, which outline your body’s inner workings throughout a fast using your own unique data.

Tip: Are you an iOS user? Add Timer widgets to your iPhone lock screen, home screen, and/or Apple Watch! Are you an iOS user? Add Timer widgets to your iPhone lock screen, home screen, and/or Apple Watch!

FAQ

Can I Have Water on a Fast?

Absolutely! In fact, you should be drinking plenty of water to ensure that you stay hydrated. (And yes, you can have non-caloric sparkling water.)

Can I Have Coffee and Tea on a Fast?

Yes, but it depends on your goals. Black coffee and tea have negligible calories (around 1–2 per cup), meaning they won’t break a fast or affect weight loss. But, if your goal is to reset gut health, coffee and tea can trigger digestive functions that may impede your progress.

Can I Take Vitamins During a Fast?

Pills and capsules are generally fine, but sweetened gummies or tablets can affect your insulin levels, so it’s better to take them during your eating window.

Can I Take Pre-Workout Supplements During a Fast?

It depends. Most pre-workout supplements contain carbohydrates that do break a fast, but caffeinated supplements are usually A-OK. To be sure, look at the supplement facts label. 

What If I Get Hungry While Fasting?

Feeling hungry while fasting is normal, and the worst of it will go away as you build your fasting practice. But if your hungry is turning into hangry, you can try drinking sparkling water or a cup of tea, going for a walk, or taking a few moments for mindful meditation.

What If I Forget to Start My Timer?

No problem! You can always go back and edit your fast’s start and stop times by heading to the Timer and selecting “Edit Start.”

When Should I Stop My Timer?

Stop your Timer right before your first meal of the day, whether it be breakfast, lunch, or dinner. (We call those meals “Fast Breakers.”)

What Are Fasting Zones?

As you fast, your body goes through many different stages, called Fasting Zones. Fasting Zones are based on the work of our Scientific Advisory Board and personalized using your own health data so you know when your body is burning fat, using up ketones, and performing other fascinating physiological feats.

Tap here to learn more about Personalized Fasting Zones and how they can optimize your fasting journey. to learn more about Personalized Fasting Zones and how they can optimize your fasting journey.

What Are Challenges?

Challenges are a fun way to stay motivated, unlock badges, and level up your stats. Zero has both monthly and ongoing Challenges that range from logging four fasts to spending 10 hours in ketosis. And if you want to make Challenges extra special, invite a friend along for the ride!

Tap here to join a Challenge. to join a Challenge.

Where Can I Learn More?

Zero has an ever-expanding content library of articles and videos, written and curated by our team of scientific experts. We add new articles and videos every week, so be sure to check often (and subscribe to our Weekly Newsletter) for a wealth of knowledge at your fingertips.

Tap here to view our content library. to view our content library.