The Official Fasting Q&A With Ben Greenfield: Does Coffee Break Your Fast, Poor Sleep During Fasting, Amino Acids During Fasting & Much More!

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The recent Kion 5 Day Fasting Challenge has now come to a close – and we had over 10,000 people participate (that's a whole lot of food that wasn't eaten).

During the fast, I received plenty of questions about fasting, such as:

  • Does coffee hurt or harm your fast?
  • What can I do to improve my sleep during – and after – a fast?
  • What is the hormonal effect of fasting on males? And what about for women?
  • What is the best kind of fasting if your goal is body composition (fat loss, muscle gain/maintenance)?
  • Does fasting – especially 3-5 day extended fasts – slow down your metabolism?
  • What type of training is best while fasting, and what type of training should be avoided?
  • What other things can you do to enhance the benefits of a fast? (e.g. cryotherapy, enemas, etc.)
  • How should you prepare for – and break – an extended fast?
  • Is it OK to fast while breastfeeding or pregnant?
  • Does your ability to absorb food and supplements increase after a fast?
  • What are your thoughts on EAAs while fasting? Do they break a fast? And what about BCAAs?
  • And many more!

During this Fasting Q&A Solosode, you'll discover…

-How does fasting for longevity differ from fasting for things like fat loss or circadian rhythm…7:45

  • Decreasing calorie intake 20-40% is the most optimal way to regulate aging and increase life span
  • Inhibit mTOR pathway, stimulate autophagy, induce ketogenesis
  • Autophagy: “self-eating” – not to be confused with apoptosis, which is cell death
    • Autophagosomes to lysosomes “spring cleaning in your cells”
    • Eating shuts down autophagy; fasting increases autophagy
  • mTOR: mammalian target of rapamycin
    • Energy enzyme
    • ATP becomes ADP
  • Every time you eat, you activate mTOR and suppress autophagy
  • Ketosis: using fat as the primary source of fuel
    • Less oxidative stress; slows the aging process
  • My personal protocol:
    • 12-16 hour intermittent fast daily
    • 24 hour fast (dinner to dinner) twice a month
    • Fasting mimicking diet (FMD) 4x/year

-Whether coffee helps or harms your fast…16:50

  • Black coffee can enhance fatty acid mobilization from adipose tissue, alertness, metabolism.
  • Coffee without any calories added (coconut oil, butter, etc.) will help the fast

-How fasting can affect your sleep…20:05

-Hormonal effects of fasting in men vs. women…23:40

  • Lean and fit females do better with shorter fasts (12 hours); men are more versatile
  • Insulin, growth hormone, responds favorably to a fast
  • Noradrenaline increases with fasting
  • Level of testosterone increase while fasting is unknown
  • Podcast on kisspeptin

-Whether fasting can slow down your metabolism…30:45

-Tips for enhancing the benefits of a fast…33:20

-The best types of training to engage in while fasting…36:25

  • Anything that rapidly depletes glycogen or carb levels will have deleterious effects
    • HIIT
  • High weight, low reps; bodybuilding vs. weight lifting
  • Walking, swimming, yoga; something you can do and have a conversation

-How to properly prepare for and break an extended fast…38:55

  • When finished with a fast, you'll be less equipped to digest complex meals
  • Go low and slow when reintroducing foods
  • Soft cook veggies
  • Avocados, grass feed cottage cheese, eggs
  • No steaks; anything you need to chew for a long time
  • Peter Attia's “nothing burger”

-Whether or not it's ok to fast while breastfeeding or pregnant…42:18

  • Religions encourage women to refrain from fasting while pregnant or breastfeeding
  • Biochemical changes in milk in response to fasting
  • Think “feast” not “famine”

-How fasting affects your body's ability to absorb food and supplements…45:38

-Essential Amino Acids' effect on fasting…48:15

  • Don't use them if your goal is cellular autophagy
  • Can be very useful for resetting circadian rhythm, gut cleanup, spiritual benefits, etc.
  • Can be a good mTOR activator
  • Dry mouth, from amino acids:
  • GI effects:

-And much more!

Click here for the full written transcript of this podcast episode.

Resources from this episode:

Kion's Free Fasting Guide

Kion Aminos

Kion Flex

Histamine X

Histamine Block

biOptimizers Masszymes (use code GREENFIELD to save 10%)

Episode Sponsors:

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*These statements have not been evaluated by the FDA. This product is not intended to diagnose, treat, cure or prevent any disease.

Do you have questions, thoughts or feedback for me? Leave your comments below and I'll reply!

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43 thoughts on “The Official Fasting Q&A With Ben Greenfield: Does Coffee Break Your Fast, Poor Sleep During Fasting, Amino Acids During Fasting & Much More!

  1. Klára Budošová says:


    You have said that you use whole spectrum of EAA during your workout and do not use Bcaas, but in lot of product are Bcaas included in EAA supplements, so do you use just some special of the? Next question would be how is goin IF with reseting your leptin sensitivity and if can be done even with bcaa ( I like to use them during workout, because I amore energized). Thank you.

    1. BCAAs only contain 3 of the essential amino acids, so yes, BCAA supplements will contain some of the amino acids in EAA supplements. EAAs are a more complete source, which is why I recommend them over BCAAs. Feel free to call your other question into the podcast.

  2. Jacob says:

    Ben, I have the 16 hour fast thing down pat! I have been doing it for years without even knowing about it. I usually eat a big dinner before 7pm and then typically don’t eat breakfast. My first meal of the day is usually around 11 am. My question is can i take my supplements before the 16 hours is up? For example i get out the door for work about 630am and take my supplements before i leave. Should i wait until my fasting period is over to take them or am i good with what i’m doing? I’m slowly trying to get cut again like i was in my early to mid 20’s (37 now) I used to be ripped but not big. Agile like a ninja. I am currently focusing on testosterone production and sexual performance so i can keep my wife happy. I have a tremendous appreciation for what you do. Thanks a ton!!!

    1. It depends on your goals, and also the supplements. (Some supplements should be taken with food, so it wouldn't even make sense to take while fasting.) Read this article, specifically the "Do Amino Acids Break a Fast?" section.

  3. Doug says:


    I want to do a long water fast. I have done 5 days before but I am concerned about having my body utilize fat if the fat may have unhealthy nutrients and toxins. If that fat came from unhealthy eating habits (SAD) could the toxin and such cause too much stress on the liver?

    1. If you're worried about the potential negative effects, it might be a good idea to consider a liver cleanse:

  4. Stephen Ball says:

    I am trying to find a definitive answer on whether or not pure Stevia extract causes a release of insulin. Looking online it looks like the jury is still out on this as there haven’t been many human studies on this. Using Stevia in my drinks makes fasting much more tolerable for me so I would like to be able to use it if I can. However, I don’t want to risk breaking my fast so I am currently playing it safe and not using it on my fast days. What is your view on this? How about using pure Glycine amino acid as a sweetener? Does this have an effect on insulin?

  5. Yan Boivin says:

    MUSHROOMS,reishi,cordyceps,etc,do they break a fasting?can’t seem to find a clear answer,thanks

    1. Should be okay for the most part. Mushrooms are not calorically dense and shouldn't cause a spike in blood glucose… I often use Four Sigmatic Mushroom teas/coffees during fasts.

  6. connor Ferguson says:

    Hi Ben,

    After a Fasted workout how long would you leave it before taking a protein shake?. So I workout first thing in the morning around 4-5am but I break my fast around 11am (16hrs), would 11am be to late to have the most benefit from a Protein shake?

  7. Michael says:

    Hi Ben,
    Is a 12 hours IF fast just as effective as a 16 hour fast? Or alternatively, how many additional benefits of fasting are gained by fasting the additional 4 hours from 12 to 16 hours? Fasting 12 hours is reasonably easy to do. Fasting 16 takes a bit more effort and planning.


  8. David Bowry says:

    Hi Ben,

    Can I get a check if it’s Ok to take Kion Flex whist fasting, which you mention in this episode. Kion Flex contains collagen which I would have thought would have broken a fast, would it not?

    Keep up the great work.



    1. If you are doing a strict fast for the purpose of maximizing autophagy, it is best to avoid all supplements/food… If you're looking for benefits of gut health, body composition, insulin regulation, etc. then the collagen in Kion Flex will actually be supportive of restoring gut health, along with providing joint support/pain reduction benefits.

  9. Travis says:

    We did a 6 day fast with 2 day re-feed. Since then my son, wife and myself have been fasting for 24 hour periods every day. Is this a good idea. Right now my training is low when I ramp it up again I know I will have to eat more.

    When we eat dinner it is mainly protein, vegetables, and good fats like olive, coconut, and avocado oils.

    1. If they are doing such fasts, it's important that they are still consuming enough calories to fuel their bodies. Once training revs up it could be a good idea to move to more of an Intermittent Fasting protocol to ensure you get the calories, macros, mineral, vitamins, etc your body needs to support training, recovery and hormone regulation

      1. Pat says:

        Is almond milk in coffee ok in the morning or will it break the fast?

        1. I would stick to black if you're fasting, unless you're doing a caloric liquid fast.

  10. Heather A Jezorek says:

    Thank you for addressing what is known about coffee and EAAs and fasting. I am also wondering about adaptogens. I have read that they work best on an empty stomach, so I mix in a powdered blend from Four Sigmatic in my morning coffee and don’t eat for 2-6 more hours, depending upon my day. Would this decrease the benefits of a time-restricted eating plan by activating digestion/hormonal/growth pathways? Just trying to figure out how to get the best of both worlds…

  11. Debby says:

    You mentioned that lean females actually burn more fat if they eat a small amount of carbs before a work out and didn’t eat after. I was wondering what you considered a lean female. There are a lot of different opinions on that and I’m waiting to get the most out of my fasting.
    Bodyfat percentage? Active as in workout everyday or only elite athletic level?
    Thank you so much Ben. You give so much amazing information!!!

    I usually fast all day and do a noon work out and sometimes will eat after or won’t eat until after I do another work out around 5 PM. Or I’ll just do a 5 PM work out and eat after. Stand at desk most of the day but do cycling, kickboxing, hot vinyasa, and some weights.

  12. Skip Skipper says:

    Is this article accurate on mtor, DHEA and animal protein consumption?

  13. Albert Karaptian says:

    What is it about Essential Amino Acids that make them ok or better than BCAA’s for taking prior to/during fasted high volume weight lifting/HIIT/Tabata for someone looking to main muscle composiittion

    1. BCAAs are not efficiently utilized for muscle synthesis as they have only 3 on the essential amino acids. As a result, BCAAs are mostly used as quick fuel, burned as carbs… EAAs have much better utilization/absorption (Almost 99%).. As a result the amino acids are actually used for muscle synthesis and will not spike blood glucose like BCAAs

      1. Maggie says:

        Hi Ben,

        If all three BCAAs are part of EAAs than why don’t EAAs also spike blood glucose? Why does the body respond differently? Finally, if you are using BCAAs that have no calories or sugar (such as Xtend BCAAs), do they still break a fast because of this glucose spike that they cause?

        BTW, I just ordered your new Mixed Berry Kion EAAs…looking forward to trying those.

        Thanks for the info,


        1. Leucine is the amino acid thought to increase blood sugar. However, compared to BCAAs, in Kion Aminos leucine is packaged with 7 other amino acids. These other EAAs help to buffer the glycemic response normally experienced from high leucine consumption in their absence. Therefore, the insulin response for most individuals from Kion Aminos is negligible.

  14. Stefanie C says:

    Another great episode. Thank you. My question involves morning hot hour-long Hatha/Power/Vinyasa sessions and fasting. I would like to fast until at least noon, but crave protein after a morning session. I’ve considered starting my fast earlier (skipping dinner), but then I miss out on carb-sleep benefits. Then there’s not doing hot yoga in the morning (😟). Thoughts?

    1. You could try EAAs after your yoga session. They won't spike blood glucose, allowing you to maintain almost all the benefits of the fast while helping to satiate you, provide energy boost and support recovery/lean muscle mass

  15. Bill Montgomery says:


    You didn’t mention using Kion Aminos while dieting (not Keto diet, just calorie restriction). I have been using them after my workout 30 minutes before me evening meal which seems to keep me from losing muscle.

    I also then drink a protein shake with BCAAs. Maybe don’t need to.

  16. Kat Emel says:

    Great Podcast! Curious, how often would you recommend the strict/longevity fast vs. intermittent or fast-mimicking diet? Also I’m trending toward one meal a day when intermittent fasting, so do you have an ideal ‘meal’ either macros or nutrients to achieve per day?

  17. John says:

    I’m in the middle of a 5 day strict water fast. Do I need to add pink Himalayan salt to my water, and if so how much would you recommend?

    1. Brian says:

      Check out Sole, best way to go with pink Himalayan Salt.

    2. Adding sea salt to water can really help with mineral content during fasting, or just in general really. The salt can also help satiate if you're feeling hungry. Personally, I'd recommend either Colima or Celtic Sea Salt even over Himalayan, as Himalayan often has a higher heavy metal content

  18. Jason says:

    Your protocols certainly aren’t feasible for most people. For instance your sleep protocol with two of Doc parsley’s sleep remedy servings and enough CBD to hit the quota for sleep it’s going to cost most people in the neighborhood of 10 to $15 per day. I unfortunately we don’t all have the sponsorships you do.

  19. Tefta Fitsamoreandrolean says:

    Cool. I will watch you on JRE 2day. If you need any tips on fasting email me at [email protected]

  20. Ed says:

    Awesome episode – great consolidation of a lot of different learnings.

    Quick one – does apple cider vinegar +lemon with water in the morning break the fast? What if Himalayan pink salt is added to that combination too?

  21. Griff Plenert says:

    Hi Ben,
    Last year I was skiing up at Silver Mountain and had a wicked crash where I basically landed straight on my back after hitting a big ol jump. I went to a few doctors in CDA and they all took xrays and said there was nothing wrong with me. Over this past summer I moved to Vegas for work, and figured I would see what an orthopedic surgeon would see. We found out that I had pretty serious compression fractures in my T3-T7 spine and the bones had already healed in the 6 months since the spill. The doc basically prescribed me a lifetime supply of pain meds because I am still in pain 24/7.
    Do you have any recommendations on what I can do to reduce the pain? I have been intermittent fasting, cutting down on my carb intake, and taking CBD and that seems to have helped a bit to reduce the inflammation. Thanks for the help!

  22. Hervé Thibert-Hamilton says:

    Hi Ben, you mention in the podcast that, in case of cancer, you would go on a Ketogenic plant base diet. Do you know of any good resources for that? Books? Meal plans? Thank you for your help and keep up the good work. Much gratitude, Hervé

  23. Sophia says:

    Dear Ben,
    Thank you for all the amazing content! I have noticed you have been mentionined orthodox fasting in a few podcasts, would you be willing to do a podcast on how orthodox fasting effects health? Or a podcast of how major religions different fasting regimes effect health? I’m orthodox and I often wonder how the fasting we do effects us. I found a great article by Chris masterjohn about it, and there where many interesting and sad comments of people even leaving their religion over it. Thank you for all your time and hard work. Sincerely, Mahalia

  24. Virgil says:

    Amazing solo-sode, Ben! I always asked myself if the 600mg GABA that I take before sleep would stop autophagy?
    I have my own “sleep cocktail” that works great for me: one Mg l-threonate pill, one 600mg GABA pill and a cup of passionflower & chamomile tea.
    While I suppose the tea and magnesium won’t have any effect, would GABA negatively affect autophagy? It’s an amino-acid after all, but I hope(…) there is some sort of a threshold that human body has to start/stop these mechanisms…

  25. anthony Guastella says:

    Hey Ben, does topical coconut oil break a fast?

  26. Kelly M says:

    Hi Ben,

    As a female who is trying to adhere to 12hr IF and remain in a ketogenic state; what should I and how much should I be eating prior to a workout (usually in morning/afternoon)? Should I eat my carbs for the day right before I work out and avoid the proteins and fats until a few hours after working out? And, would that then mean I do not follow your protocol of a carb re-feed at night, as I would have already hit my carb quota?

  27. Peter Grace says:

    Hey Ben, great episode! One follow-up question: you recommend, as you did here, light aerobic exercise in a fasted state. Since many of us are hard charging athletes, can you help us understand what you mean by ‘conversational pace’? What would be the target heart rate zone? Or perhaps a better question, what would be the MAX heart rate that you would stay under for this type of exercise?

    1. This is typically in the 70-80% range and describes moving at a rate in which you'd be able to maintain a conversation with another person without shortness of breath dramatically limiting your ability to speak… Here's a great resource to dive deeper:

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