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How to Hack a 7 Day Fast in 24 Hours

Nick Norwitz MD PhD

157,497 views

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As a bit of behind-the-scenes news, they've also asked me to help design a clinical trial aimed at developing a diagnostic rubric to identify the people most likely to benefit from exogenous ketones. If you have ideas for biomarkers, clinical characteristics, or other factors that should be included, I'd love to hear them.

Feel free to share your thoughts in the comments—I genuinely enjoy crowdsourcing ideas from this community.

Resistant Starch Visceral Fat Video: How to Lose Visceral Fat in 8 Weeks (Prove...

Description
A remarkable study published in Nature Metabolism tracked nearly 3,000 circulating proteins while healthy volunteers completed a medically supervised 7-day water-only fast. The findings suggest that prolonged fasting isn't simply about burning fat—it may trigger coordinated biological changes affecting metabolism, inflammation, cardiovascular health, brain biology, and immune function. In this video, I break down exactly what happens on days 1–2, days 3–5, days 5–7, and during refeeding, while explaining why the 72-hour mark may represent a critical metabolic threshold. I also explore an important practical question: can you reproduce these fasting-related changes without completing a full week-long fast?

Chapters
0:00 – What Happens When You Fast for 7 Days?
2:30 – The Study Design and Methodology
4:30 – The Fasting Timeline: Days 1 to 10
7:34 – What Happened to Lean Mass vs Fat Mass
9:39 – The Big Twist: Day 3 Threshold
16:23 – How to Hack a 7 Day Fast with Exogenous Ketones
21:00 – The Favorite Exogenous Ketones
22:07 – Different People Appear to Have Different Ketone Thresholds
24:12 – How to Break a Prolonged Fast
25:52 – A HUGE THANK YOU… And What’s Next…

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20 Comments

@kirbyaugustine761 1 month ago

Completing a workout before starting to help deplete glycogen stores before embarking on your 24 hour plan helps speed up ketosis as well.

@fernandosantana271 1 month ago (edited)

I used 3 seven-day fasting to create a tolerance towards alpha-gal antibodies within eight months I was able to have all mammalian derived foods. That was 2 years ago and still going strong.

@Freedom-rz7xp 1 month ago

Thanks Nick! I'm definitely trying this! Also, I found a way to get my ketones to 4 and above with just a 3 day fast. May be a less expensive option for those who don't want to fast for 7 days but also don't want to pay for expensive BHB. It was my attempt to recreate a sardine fast without the sardines as I can't tolerate them due to histamine intolerance. Anyway, this was my protocol, basically a fat fast. Days 1 and 2, I would have 2 tsp of real olive oil plus a few MCT oil capsules every 2 to 3 hours while awake. I would lay off the MCT by 2pm so that it didn't interrupt my sleep but continue the EVOO until bed. Important note: don't buy the garbage sold in regular grocery stores. The olive oil has to be single origin high quality olive oil. I get mine from olive oil lovers (no, I don't get money for recommending them!) But Costco has a few select offerings (bland in my opinion but still real olive oil). Lots of videos on youtube about how to tell if the olive oil is real and not mixed with seed oils. Anyway, by the evening of the second day, my ketones are hitting 3 to 3.5 and by that point I stopped the olive oil and MCT and just did a water fast. By mid day on day three I am in the 4 range. Ive continued for a full 4 days but have found by then that my nervous system is off the wall, felt super anxious, unable to sleep etc. Not sure if it is a cortisol issue or what. But I usually break the fast at that point. I also actually spend two full days breaking the fast...the slower the better. I always start with 30 Recovery Bits which coat the lining of the gut and prevent any unfortunate gut issues. An hour later, bone broth. This absolutely recovers my nervous system and the anxiety stops. Incidentally, (and don't yell at me if you think this is a bad idea), I also use chatgpt to guide my fast....it's more mental than anything! It helps me to keep going and I have found it really guides the breaking of the fast in a controlled way that prevents refeeding syndrome and maximizes the benefits. It's like having a fasting buddy cheering you on!

@waynewells2862 1 month ago

I used to do a 6 day fast once every year. I am a thriving survivor of aggressive CLL/SLL and oligometastatic prostate cancer diagnosed in late 2018 and have had only 3month depot shots of Lupron (ADT) as a therapy for the PC which I paused in Dec of 2025. So far so good. During Cancer years and chemo with the leukemia I did periodic 4 day fasts every 2 months. I gave up fasting two years ago because of muscle loss ( I am now 83) While I attribute fasting to the lion's share of my success I was getting muscle wasting from years on Lupron so I chose to suspend fasting. not sure how to handle this dilemma. Have gained back some muscle and feel much better at 7+ months off Lupron. fascinating video!

@patriciakacprzak6510 1 month ago

Great video, as always !We have to talk more and more about fasting beyond fat loss . It makes small people be afraid of longer fasts and people who lose all the weight ( and regain it cause they don’t change their lifestyle ) gain the weight back. I’ve been fasting since I was 17 ( 45 now ) not for weight loss , in 5.1ft 100 lbs. I’ve done multiply 7 day fasts , shorter and I do 18-20 h daily , so many benefits !!!!! Mental , emotional, spiritual !!!

@iam-smcs 1 month ago

Skip explanation to 16:23

@m.j.s.3838 1 month ago

A few weeks ago I did a ten day fast, no problemo. It started at one day, to see how I felt. Felt fine, so kept going to three days, and so on to ten days. I had water, coffee and tea. I did a few fasts in my thirties and wish I kept it up. The ten day fast really helped a knee that has been bugging me for two years and only getting worse, my sleep is better, too. I did not weigh myself before or after, because I'm interested in health not weight.

@jeagr209 1 month ago

I gave myself refeeding syndrome a year or so ago, eating too many carbs, too quickly after a 5 day fast. (Big Mac + Large Fries + Large Diet Soda + Large Payday candy bar). Ended up in the ER. Symptoms were extremely low blood pressure, and a heart rate of 132 that lasted for 2 days. Ended up having to get an electrolyte IV. Lesson learned.

@3pmnrg 1 month ago

Just did the 24 hour with 2oz ketones at hour 19 (ketones were at 2.5) and then again at hour 23. After hour 24 ketones were 4.4!

@jeff911rn99 1 month ago

If you start the fast already burning fat (keto/carnivore) it seems you would get max benefit sooner than 3 days.

@Virgusvi 1 month ago

Something not mentioned is what happens in your mouth. Plak starts to go awry and how “clean “ your mouth feels which gets rid of the bacteria that effects your heart and body health

@Ahhappi 1 month ago

Caffeine is interesting in that the protocol “Gerson Therapy” which is a vegan therapy for cancer uses “coffee Enemas” to remove all the “cancer die-off toxins” from the body.

@boatdrinks1 1 month ago

Lets all go to Costa Rica for a deep dive into coffee

@Garseraph 1 month ago

Very excited for the new studio, and all the other stuff "coming down the pike"! 😃

@desertself7538 1 month ago

Very cool episode. A few thoughts: we know that using exogenous ketones does not give nearly the full physiological and chemical change as naturally produced from keto diet. Therefore , we really don't know the extent to which the hack mimics the researchers results. Also , it would be so interesting to do the exact same research with people already keto and see what the timeline is. And of course , it would be interesting to do the exact same research where exogenous ketones were added at various timelines. Thank you again, Nick.❤❤❤

@tongsan523 1 month ago (edited)

Nick, I have a suggestion for protocol. Instead of doing 24 hours water fast after taking BHB, do 24-48 hours dry fast instead.

@Joshua.Edwards 1 month ago

Studies show the “best bang for your buck” benefits drop after 72 hours. It’s like driving a car at its best MPG, why would you redline the engine or sit in neutral? Take it for a nice spin at the engine’s most comfortable speed and then let it rest before you take it out again. 😊

@yelenamarycheva8175 1 month ago

I read that exogenous ketones usually stay in the body for 3-4 hours, max 6, if you are resting. So, how many keton drinks do you need for a day? This brand- Kenetik is a good quality product, but pretty expensive. Ordered it ones, but not anymore. Plus, i think that the natural way is only one to go. Physiology is so complicated and simply raising keton level with keton drinks will not result all this beautiful changes in you body. Needs to be studied:)