April 21, 2020


#108 – AMA #13: 3-day fasting, exogenous ketones, autophagy, and exercise for longevity

“I think once people enter that seventh and eighth decade, if they haven't done a lot of consistent preparatory work in the decades prior, it's alarming how quickly things go south.” —Peter Attia

Read Time 14 minutes

In this “Ask Me Anything” (AMA) episode, Peter explains some observations he’s noticed since switching to a 3-day fasting regimen, the various things he’s measuring, and some helpful tips for getting through a prolonged fast. He also discusses the role of exogenous ketones in fasting and ketogenic diets as well as their impact on autophagy, specifically. Finally, Peter provides some practical advice for those looking to fit exercise for longevity into their busy life. Once again, Bob Kaplan, Peter’s head of research, will be asking the questions. If you’re not a subscriber and listening on a podcast player, you’ll only be able to hear a preview of the AMA. If you’re a subscriber, you can now listen to this full episode on your private RSS feed or on our website at the AMA #13 show notes page. If you are not a subscriber, you can learn more about the subscriber benefits here.

We discuss:

  • Peter’s observations since switching from a 7-day to a 3-day fasting regimen [1:25];
  • Ketone measuring devices—blood and breath [7:40];
  • Can zero-calorie sweeteners affect ketone production? [10:40];
  • Will there be a continuous insulin monitor anytime soon? [11:55];
  • Exogenous ketones—Role in fasting and ketogenic diets and their effect on insulin, blood glucose, and autophagy [14:10];
  • 5 tips to help you get through a multi-day fast [25:55];
  • Relationship between BHB levels, glucose levels, and autophagy—Are high levels of ketones enough to produce autophagy? [34:10];
  • Why is measuring blood insulin so much harder than blood glucose? [36:55];
  • Advice and resources for people wanting to stay up to date on developments related to health and longevity (and how to quickly sift through all the bad science) [40:10];
  • Advice for those looking to fit exercise for longevity into their busy life [51:10]; and
  • More.


Peter’s observations since switching from a 7-day to a 3-day fasting regimen [1:25]

Switching from 7-day fasting to 3-days fasting

  • Previously, Peter has been doing 7-day fasts once a quarter
  • For 2020, he has switch to a 3-day fast once a month
  • So he’s still fasting a roughly equal amount of time per year in total
  • The rationale for the switch was twofold:
    • 1) 7-day fasts are quite intrusive on life
    • 2) In doing the 7-day fasts, Peter has noticed that on the second day of his fasts, his glucose levels will normalize and his ketone levels really start to rise — so something interesting is happening at that point so at least doing a slightly less extreme version (3 days) will give him some of that benefit that we got from the seven day fast

-Observations about the 3-day fast compared to 7-day:

{end of show notes preview}

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  1. Laughed so hard when Bob made the NAMBLA reference. Looking forward to the future nerd safari podcasts where you really get into the weeds with AMP-K, BHB, the suppression of insulin, cell energetics, and autophagy.

  2. You mention Peter subscribes to the categories of Basic, Drugs, and Caloric and Dietary Restriction from Obesity & Energetics. Is there a way that I’m not seeing that enables a subscriber to identify 2-3 categories & get only information/ etc. specific to those few titles, rather than a lot of info’ one is not interested in?

  3. Peter,
    I am so fascinated by you, not only what you know and embody but how clearly you use different models/systems in delivering material! I have been listening to many of your podcasts/videos and find them extremely addicting. Can I get away with asking 1 tactical question…I have 1 kidney, 63 yo, 193lbs, love health & fitness, have experimented and documented with a variety of tactical approaches AND I still have fluctuating high blood pressure 115-145 taking lisinopril which I badly want to eliminate? Any advice and/or direction would be tremendously appreciated in lowering my blood pressure!!

  4. As always , AMAZING information,clearly explained. I am a Psychiatrist taking care of adults,adolescents and children and the concepts ennunciated provide me with useful data to transmit to my patients. Kudos to you and your team. I do agree,it is addictive. Luisa Fijman M.D.

  5. Very nice review of material that has been covered previously. I am curious to know that if fasting for 7 days is beneficial, and possibly 3 days every month too, then why not 1 day a week? Is it the length of the fast that matters or something else? I realize that there is no ‘dose’ that is established for this, just like there isn’t one for exercise, but would love to hear Peter’s thoughts on say fasting every week from say Saturday night to Monday morning (36 hrs) or from Sunday AM to Monday AM (24 hrs) on his next AMA.

    Pradeep Bansal, MD

    • You bring up a very interesting point – particularly impressed by your math skills. So instead of 7 days, one can do 1 day a week. Or instead of 1 day a week, may be 1 hour every day for 24 days. Same effect!!

  6. Usually in my 20-24 hours fasts my Ketones levels are around 3,5 mmol which freaks me out and prevents me from going over. I know, as Peter mentioned, it’s impossible to drown in a shallow pool but and don’t want to be over 4,0 mmol. I guess every body is different but it frustrates me not getting to the great autophagy benefit

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