How to do a 65 hour water fast


Prolonged fasting has a slew of benefits, improving metabolic rate (who doesn’t want faster metabolism!?), decreasing inflammatory markers, lowering insulin, revitalizing our brain cells, and inducing the process of recycling cellular waste and damage. It can help us live healthier for longer, and who doesn’t want that ?

So, what's a water fast ?

A water fast means not ingesting ANY calories for a prolonged (over 24 hrs) period of time. You essentially drink water, tea or black coffee (without milk/cream or sugar!) and go about your day knowing that rejuvenation magic is happening inside your body.

Now I’m all for biohacking my way to live to 150, but prolonged fasting has been something I kept putting off for a while. 

Truthfully, I was scared.

I love food too much, I thought, I’m that person who gets “hangry”…there’s no way I would survive.

Well, I set out to do a 48 hour fast, and accidentally ended up going for 65 hours. Oops.

Turns out fasting is WAY easier than I imagined.

Disclaimer: I’m not a doctor and the following is an account of my personal experience and learnings. Consult with a medical professional before following any recommendations.


Here's how I did a 65 hour water fast and what I learned along the way:

First, outsource the task of counting the hours to an app. You don’t want your mind to always be trying to count the number of hours since you’ve eaten – ignorance can indeed be bliss when it comes to time !

Choose a method for tracking your fasting time

I used Zero tracker, which is rated 4.8 stars with 75K+ ratings on the App Store. It's mainly an app for tracking daily intermittent fasts (as you can see from my data in the screenshot), but you can also use it track a prolonged fast - you just keep the time running.

 I started my fast after dinner on a weekday.

  • To be honest, my decision to do this fast was pretty spontaneous. It just so happened that for the next couple of days I had no dinner plans and the weekend/following week wasn’t looking as promising, so I thought now is as good of a time as ever.

  • Some people prefer to fast over the weekend, fearing energy drops (and perhaps that’s the way to go if you’ve never done a fast before!), but I decided on weekdays as a different type of precaution. The fridge and pantry are just way too accessible on the weekends – I was about to do my first ever prolonged fast and wanted to avoid temptation.

3 hours (bedtime): started feeling hungry which must’ve been psychological since I’ve been circadian rhythm intermittent fasting for about 2 weeks prior, would normally  finish eating by 5-6pm and not feel hungry going to sleep knowing that I’d eat in the morning.

Just the idea that I wouldn’t be eating in the morning set me off I guess.

Learning: try to chill out and not think about it, the longest fast ever recorded was 382 days so a couple of days of fasting is a drop in a bucket.


12 hours: felt fine upon waking up, no hunger pangs which was SHOCKING to me since I’m one of those people who goes to sleep excited about breakfast and wakes up ready for food immediately. But surprisingly, I was fine. So I did my morning routine, some light pilates, had a green tea and went to work.

15 hours: feeling some hunger pangs I think my body was ringing the alarm that I was nearing lunchtime and I hadn’t even had breakfast yet – like what is this !? Need snacks !

Learning: Women and men differ in how long it takes to empty liver glucose stores. For men it can be as much as 16 hours or longer (hello, the popular 16:8 intermittent fasting schedule!), while women can reach that point in 14 hours. So my guess is the hunger pangs could’ve stemmed from having depleted my glucose stores and the body going through a transition of entering nutritional ketosis, which is a survival mechanism whereas your body beginning to burn fat for fuel instead of glucose.

18 hours: I kept drinking water and was back to feeling fine, lighter, and no fatigue. Also, having a full schedule of back to back meetings helps with not thinking about fasting as much as jumping from meeting to meeting.

Learning: keeping yourself busy and immersed in other activities helps the time go by faster so that you’re not thinking about how long it’s been since you’ve eaten or assessing whether or not you’re hungry.

20 hours: really surprised that I’m still not experiencing any fatigue or energy loss. I was definitely aware that I had an empty stomach (aka not even a hint of a “food baby” was definitely new) but there was no discomfort and my stomach wasn’t growling at me. 

Learning: switching it up and having sparkling water can help if you want to trick yourself into feeling full for a while. 

24 hours (7:40pm): the hunger pangs kicked in at this point because my body knows I usually would’ve had dinner by now.

Learning: I found it interesting that the feeling of hunger would kick in around typical meal times, whereas once the hour or so passed, I’d completely forget about the fact that I was fasting. Psychologically we are such creatures of habit it’s interesting to see how the body adapts to new behaviours and situations.


36 hours: Woke up from a night of very vivid dreams. I don’t remember the last time I had such vivid dreams in succession over the course of one night of sleep. I also woke up at 4am and then a few more times before my actual wake-up time. This is also unusual. Interestingly in the morning I felt completely content, no hunger whatsoever.

Bonus: once you get past 36 hours, that is when the process of autophagy really starts to ramp up.

  • Autophagy is the process of cellular waste and damage removal, which is inhibited when your body is busy digesting food, but oh so important for keeping the body healthy and operating efficiently.

My sleep data after sleeping in a prolonged fasted state

Despite staying up in front on the computer later than usual the night before, my REM sleep (which is a struggle for me), hit a stronger score than I was able to reach all week.

Heart Rate and Heart Rate Variability scores while sleeping in a prolonged fasted state

Sleeping about 30 hours into my fast, I hit a low heart rate and my highest average Heart Rate Variability rate ever at 86 ms. The highest healthy average for my age group and gender is reported at 65.7 ms (see image below). It turns out without the burden of digesting food, my body entered a completely relaxed state, focused on recovery and repair.

Standard HRV scores by age and gender. (Voss A et al., 2015)

What is HRV? HRV measures amount of variation in the intervals between heartbeats. While HRV rates are affected by age, health, and fitness, a higher HRV rate is indicative of increased fitness and youthfulness. Additionally, HRV is indicative of your biological age, which is influenced on your lifestyle choices, and can vary from your chronological age.

I did feel a bit lethargic in the morning which I mainly blamed on the several wake-ups in the early morning but after having a green tea I was feeling ready to take on the day.

Even did 3 sets each of push ups, ab exercise reps, and squats. Nothing major, but truthfully I didn’t expect to be doing any form of exercise while fasting. If anything, I felt clear minded.

43 hours (1:40pm) – my stomach growled at me around this time but within 30 minutes I was back to feeling no hunger at all. Seems that my body was adjusting this fast.

48 hours – I was lying down in a yoga studio room, about to start a sound bath meditation for the next hour and a half. So although my personal goal was to reach 48 hours, food wasn’t really on my mind. After the session my friend and I went for some tea and I never eat so late in the evening, so I figured I’ll just fast through to the morning. No biggie, I wasn’t even feeling hungry then since I was out of the timeframe of my usual meal time.

60 hours – can I mention my skin !? I don’t remember the last time it was ever so clear ! All those sayings about clear skin starting from the inside were right !

At this point I was going to break my fast but I had a few errands to run which I wanted to get done in the morning before stores and services got too busy, so I just went for it.

And by the time I got home it was less than two more hours before I hit 65 hours of water fasting, so I just went for it !

And that’s how I accidentally fasted for 65 hours.


How to break a water fast:

Breaking my 65 hour water fast with kefir, fermented milk.

Don’t feast immediately after breaking a fast. Allow your body to adjust to digesting food again. Drinking a glass of hot lemon water or in my case, I had a glass of Kefir, which is fermented milk full of probiotics to help get the gut up and running again. 

Basically, go for something that will start up your digestive enzymes before you eat.

Then eat something light with a low glycemic index. Some nuts or veggies are a good idea. You don’t want to be spiking your blood sugar at this point after all the fasting you just did. 

I waited an hour after my glass of kefir and had a veggie salad.

If you eat meat, it’s a good idea to hold off on that for another hour as it’s pretty complex for your gut to break down and digest. 

And if you’ve ever wanted to try a ketogenic diet, now would be a great place to start since your body is already in ketosis !

Would I do another water fast ?

Honestly, the fast was not bad at all. I had no trouble falling asleep, and experienced no fatigue.

The key is to drink PLENTY of water to stay hydrated.

Would I do it again ? Absolutely.

I’m all for enhanced metabolism, clear skin, and enhanced brain function. 

I think from now on I’ll start incorporating one to two 24 hour fasts per month or one 48 hour fast every few months, on top of keeping up a regular schedule of 13-16 hour daily intermittent fasting.

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