Fast With Zero

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Fast with Zero

We’re declaring 8/16 National 16:8 Day. To celebrate, we’re inviting everyone in the Zero community to mark their calendars and participate in the largest group fast we’ve organized to date. Some favorite influencers and brands will be getting in the mix, so make sure to follow us on Instagram, Twitter, and Facebook for all of the latest updates.

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Participants can begin their fast as early as 8pm local time on August 15th and complete their fast before the end of the day on August 16th.

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Get Involved

Follow @zerofasting, share photos of your in progress or completed 16:8 fast with the hashtag #FastWithZero, and tag @zerofasting. Bonus points for searching the hashtag to see others’ progress and cheer them on along the way.

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Giveaways + Q+A

We’ll be selecting lucky winners throughout the day to win fasting kits with products from Pique Tea, Kettle & Fire, Sleep Remedy, and Charlotte’s Web. We’ll also be hosting a live Q+A with Zero Chief Medical Officer, Dr. Peter Attia—tune in via Instagram or Facebook Live at 10am PT on 8/16.

Submit your questions early in the comments below.

#FastWithZero on Twitter


  • What is your recommendation for fasting and exercise? If doing a multi-day fast, is good to continue with an exercise routine?

    • Just go with it normally and see how your body reacts. Listen to that and adjust.
      I’ve been doing 16:8 for 5 years now and I’ve always worked in a fasted state, either with 10 hours fasted or at the end of the 16h window. Never had problems, my body seems to handle it very handle with any intense exercise. I’ve also worked out after 24h of fasting and was all great.
      This is my experience, see what’s yours 🙂
      You can check on some videos of Thomas DeLauer on Youtube for details as well.

  • I do intermittent fasting 6 days a week using Bulletproof coffee, is that something that you guys approve?

      • It’s not allowed on a clean fast, technically you’re breaking your fast with it so depends on what you’re trying to achieve.

    • I would assume the caloric intake for that would break the fast, if you are taking that while fasting.

    • From what I understand… especially during an Intermittent Fast… 20:4, 18:6, 16:8, 12:12. You want Zero(hence the website, maybe) caloric intake. Water only. Black coffee with nothing added is ‘ok’.
      Otherwise you are simply not ‘fasting’
      You want Zero enzyme, and liver response outside your feeding window. Putting the body into a ‘fasted’ state. That’s when the truly amazing happens.

    • Coffee (Caffeine which is xenobiotic)still needs to be metabolized by the body, so technically you are not fasting anymore…

    • It depends on what you want. You break the fast but you keep your body relying on fat.
      I used to break my fast with Tea and MCT oil to maximize even more the fasting period, but during the 16h I do, I wonly get water, black coffee and tea. No BCAA’s, No sweeteners, No Nothing 🙂

  • 16 hours seems like a breeze now that I started with Zero fasting about 2 months ago. Looking forward to tomorrow and doing a mass fast!!

  • I try to workout 6 times per week and find the morning is the best time. I generally start my fast after dinner and end the fast at lunch time. Is it ok to workout fasted and continue the fast another 4-5 hours? I am not an athlete or looking for any specific gains, just overall health.

  • Massive fan of Dr. Attia’s work, thanks for all the information you shared and will share.

    Quick one: when I start a fast, when exactly should I start counting? Just after I finished the meal before the fast or shall I wait some time? If the latter, how long?

  • I love Zero as well as fasting. Trying to make a difference for myself and zero helps me more than i have thought.

  • How compatible are prolonged fasts with endurance training, especially those that last longer than 24 hours? How should athletes adapt rest and recovery when including prolonged fasts in their diet?

  • 6 weeks in and haven’t noticed any weight loss yet. Work out at least three times a week; climbing, hot yoga, running or cycling. Not as hard as it was at the start, however if I’ve had more intense workouts, I find it much more difficult to maintain the fast the next morning.

  • I have been doing 16:8 fasting as a lifestyle change for a little over a month now. Because I have a family and treasure family dinners together I cannot begin my fasts any earlier than after dinner – usually between 8 and 9pm. I am a very early morning runner, due to having to run before my family is up, and run almost daily! This means I run in the middle of my fasts. I feel great still, but am curious what insight you have on doing this. Is it still beneficial to run in the middle of a fast? Is it less beneficial than if I were to run near the end of a fast?

  • Would you get any of the benefits of autophagy if you consumed some fat during an extended fast (3-5days) but negligible protein and carbs. Say in the form of a bulletproof coffee.

  • Have you considered specific ways to optimize refeeding since that is when “the magic happens”?

    Stem cell proliferation is one of the great benefits of post-fast refeeding. Any thoughts on ways to optimize proliferation and differentiation? Will exercise during refeeding aid stem cell transcription?

    Any thoughts on autophagy enhancers prior to prolonged fasts? By that I mean load up on quercetin, resveratrol, hydroxy citrate, spermadine in the days and weeks prior to fasting.

    Citrus bergamont is associated with activation of autophagy. What do you think of citrus bergamont tea (typically in the form of Earl Grey tea) as an autophagy aid?

  • i generally fast every day for at least 20 hrs. do you believe, over time, this could have a negative effect on my
    metabolism, given that essentially eating only once per day, i eat far less calories than if i were eating all day long?

    • seems from watching him speak… Dr. Attia eats only once a day…
      but… he says he eats a lot!! When he does… the idea is to eat well still, just inside your feed window… the smaller the window, the more you need to be conscious of getting enough good food. Dr. Attia looks in great shape, and is a testament to his own advice.
      I myself do more 18:6’s now(after 1.5 months of 16:8’s) and I eat really REALLY well in that window. And I am frankly amazed that I am not gaining any weight. In fact, down almost 30lbs in the last 60 days since doing this. Thanks Doc!! Blessings!

  • What do you do about electrolytes especially on multi-day fasts? Is mineral water often enough, or do most people tend to do better by cranking up the sodium and keeping some amount of magnesium and *maybe* even potassium in the mix? Any brand recommendations that don’t include citric acid, etc.? Thanks.

  • I’m still early into my intermittent fasting journey, so still working on getting my eating right.

    Is it still possible to experience weight loss if you end up eating the same number of calories in a time-restricted 8 hour feeding period as you would not fasting (say, over 12 hours)?

    • I think that’s the key of this. Same calories… quality foods… just all inside your feed window.
      It’s like filling your gas tank all the way while you can… then driving 16 or 18 hours to the next filling station. And filling it up again! 🙂

  • Signed a new lease in a new city and having a margarita to celebrate! THEN I’m starting the 16:8 Fast! My hubby and I are a good fasting team. 🙂

  • Almost 2 months since starting with Zero
    Harder the first few times… week or so

    16:8’s and then more 18:6’s, one 24hr fast, one 36hr ‘monk fast’… and a 64 hour fast a couple weeks ago for my 50th birthday… feeling great, down from 332 pounds to 304lbs… eating great in my feed window… exercise about every day as well
    Surprised how much I eat, and still keep the weight down… Blessings!!
    Looking forward to tomorrow!

  • Thank you Peter Attia for sharing all of your knowledge! If you could choose 2 labs to run to assess someone’s current state of metabolic health, what would they be?
    Thank you!

  • I’ve been doing 18/6 for most of the year & I don’t find it a problem. It is best/helps if I stay out of the kitchen!! It helps me maintain my weight & I trust that it is a good lifestyle to adapt. I really enjoy using zero.

  • Recent blood analysis has shown that since strictly adhering to time-restricted feeding, I’ve witnessed significant improvements in my Hba1c, Triglycerides, Glucose Tolerance and overall metabolic health. However, my Testosterone as dropped (28 –> 23.5 nmol/L) and my SHBG has remained stubbornly high (59 –> 60 nmol/L). As such, my Free Testosterone is approximately 342 pmol/L.

    My question: Does a time-restricted feeding window (e.g., 16:8) adversely affect Testosterone, SHBG and Free Testosterone (or other hormones)? If so, do you think there are benefits in taking breaks from this protocol? Are there additional things that one can do which can improve these biomarkers whilst fasting or adhering to a time-restricted window?

  • Please speak to hypoglycemia in non-diabetic healthy gen pop during prolonged fasts — 3 to 7 days. How low is to low (mg/dL)? Any red or yellow flags to watch out for if hypoglycemic?

  • I fast 20 – 24 hours a day 5 days a week and about 16 on weekends aerobics in morning weights in evening I’m 63 feel like I’m 43 to minerals and a few vitamins and wheatgrass

  • I do early morning weight training in fasted state and break my 16 hr fast in the late afternoon. Can I extend the fast to 18 hr or 20 hr and still build muscle with weight Training? Is it safe?

  • My mother has a very sugar- carb- and seed-oil-heavy diet. She is in her 60’s has started getting health problems like worse eyesight (AMD) and polyps in her gi. Could these health problems be attributed largely to her diet. Should i push harder for her to statt fasting?

  • Peter, love the drive podcast and your involvement with the zero app.
    Can you comment on the individual variation of ketone levels. Some individuals on a 5 day extended water fast seem to reach 3-5mmol/L, while others might top out at 1-2mmol/L. Is this good bad, and any way to up lipid mobilization.

  • I started Zero fast maybe a month ago. It’s great to have the reminder and showing my progress. My mother in law introduced me to Zero.
    #FastWithZero @zerofasting

  • Q: my blood pressure lowers when I fast, but only systolic significantly. Ie:120/80 average to say 104/74 this morning. Are there “ideal” values to blood pressure in the “normal” window under 120/80 that we can aim for? And why would systolic change more dramatically than diastolic?

  • Using the Zero app has been such an incredible motivation to help me stick with 20:4 fasting for nearly a month now.

    Is there a particular fasting pattern that is recommended for weight maintenance once I hit my weight loss goal?

  • I very recently started IF, by the 14 hour mark, im so hungry that water just doesn’t cut it for me…. And black coffee and tea is just not for me… I read somewhere that if I were to have a tea with a splash of milk (under 30 cals) that it wouldn’t break my fast. I’m wondering how true is that?

    On another note, I really like your app, just wish there were more widget style options 😛

  • Zero has helped me in the past to get my self in check! What a great day to get back on track with the 8/16 fast! Thanks for the inspiration to everyone joining in.

  • To be eligible for prizes how do we enter the drawing? Is it automatic when u begin your fast with zero tonight?

  • What have you found as the best story to use to seek others on the feasibility of doing 16:8/18:6/24/36 hour fasts, when it comes from the “crazy person who does 5+ day fasts”, to reduce the response of, “so sure 36, 24, 18 or even 16 hours of not eating might be fine for you, but I could never do that because I get hangry if I don’t get breakfast.”

  • How much is too much weight to lose? I’ve been doing 16:8 with a few longer ones mixed in as I feel to. I have dropped 10 pounds per month. I have been getting a fair amount of moderate exercise from walking and hiking.

  • Hey there! Fasting has become part of my life and I absolutely love how in control I am with the Zero App.

    I was just wondering if there is a way to participate in the giveaways if you didn’t have social media?

    Thank you!

  • I have started my most recent fast yesterday on the 15th of August at 19:45 and completed it today at 14:20, totalling 18 hours 35 minutes. Overall it was my fast #300, with a streak of 227.
    I feel fabulous!

  • Yes!! Finished my 16:8 at 12:30pm PST!
    Feelin’ Great…! First a good bottle of good kombucha to get the stomach prepped… Then a big fat veggie burrito bowl loaded with sofritas!! Time to chow!! ????????????

  • In addition to intermittent fasting, is it important to maintain a consistent, daily time-restricted feeding schedule? In other words, is it important to break one’s fast at the same time each day, eating each meal at the same time of day, on a daily basis, within a given feeding window? Or, should one’s goal be to eat all meals within a given time-frame, inside a daily feeding window?

    For example, my maternal grandparents, who lived to be in their 90s, maintained a consistent daily eating schedule which would be described as early time-restricted feeding. Is it likely that this (e-TRF) contributed to their longevity?

  • Howdy! This article couldn?t be written much better! Looking at this article reminds me of my previous roommate!
    He constantly kept talking about this. I will forward this post to him.
    Fairly certain he’s going to have a great read. Thanks for sharing!

  • HI – can you confirm that all of these will break the fast – ?

    green juice (no fruit)
    Garden of life Sport protein powder with water
    wheatgrass shot
    ketoba (or any ketone BHB supplement)

    Thank you. This would be a great help. I’m currently using the 16:8, with a 24 hr water fats every 2 weeks. I’m exercising a lot.

    • If the green juice has calories, the yes.
      Protein powder – yes
      Wheatgrass – Does it have calories?
      Ketone’s are a worthy of a dedicated post!

      • Exogenous ketones as they relate to fasting is a really fascinating topic, so we’re going to write an article about it. I think they can be very helpful to a fast, but there’s nuance that is worth exploring.

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