My 100 Hour Fast Experiment

Siim Land

At the beginning of this year, I took part of a meditation retreat, during which I decided to have my first 100 hour fast experiment. This totalled in at 4+ days.

You Fasted for How Long?!

No, it’s not a typo – you read that correctly. I fasted for 100 hours without food or any other form of calories. I drank only water and herbal tea with some salt in it.

Before you condemn me as insane and lock me up, let me explain you why I did it.

There are just so many profound health benefits to fasting. It has been practiced ever since antiquity for medicinal, spiritual and cognitive enhancing reasons.

For instance, intermittent fasting (IF):

  • Improves cellular functioning by increasing mitochondrial density
  • Self-digests and detoxifies the cells via a mechanism called ‘autophagy’[i]
  • Enhances human growth hormone (HGH) by an astonishing 1300-2000%[ii]
  • Reduces inflammation and blood sugar levels
  • Protects against malignant tumor growth, neurodegerative disease and cancer
  • Increases longevity and life-span

In addition to that, I did it as an experiment to see how my body would react to complete abstinence from food. Up to that point, I had been doing IF for about 5-6 years and have eaten one meal a day for several months. So, my metabolism was already well adapted to handling this.

100 Hour Fast Results

I weighed about 85 kg (187 pounds) and was around 10% body fat. In the end I was 83,5 kg (184 pounds) and 9% body fat. Now, that isn’t much at all, given my caloric deficit was at least larger than 10 000 calories. My hypothesis is that my body simply became so keto-adapted that it was able to sustain itself at a very low energy expenditure because I had already been following a ketogenic diet.

siim land black and white
siim land black and white

In terms of muscle or strength loss then you would think that I lost all my ‘gains.’ What happened really was anything but the like – I lost zero muscle mass and my physical performance did not suffer at all.

Oh yeah, on day 4, I decided to hit the gym and see how my body was going to respond. Given the circumstances – not having eaten anything for nearly 100 hours – I did excellent. There was no fatigue, hypoglycemia or muscle weakness. Instead, I was able to lift almost as much weight I previously could.

What exercises did I do? Heavy backsquats of 120 kg (265 pounds) for reps…followed by muscle ups on the very same barbell. This was about 80% of my maximum and it still felt as if I had a lot of fire left in my tank. Nevertheless, I didn’t feel the urge to push myself any further – I had already accomplished enough.

Day One –
Just the Usual

At 6PM January 1st 2017, I took my last mouthful of food and started fasting. Despite me not going to eat anything for days, I didn’t indulge or overeat. Instead, I had a standard ketogenic dinner that was low carb and high fat. What you eat before your fast is actually very relevant (more on this soon).

In the morning, everything took its habitual course. I was eating only one meal a day already so I didn’t feel any different. Over the course of the coming hours, I drank just water and was being productive.

In the evening, everything felt as great. Although I was nearing the time I usually have dinner, it wasn’t anything dreadful nor did I feel hungry because I fast for 24 hours about once or twice a month.

Some Fasting Physiology

It’s best I also explain you some of the science behind what goes on during all of this. If you want a more thorough overview, read this post.

After fasting for about 16-20 hours, liver glycogen (100-150 grams) will be completely empty. This revs up fat oxidation and makes the liver produce ketone bodies, which are fatty acid molecules manufactured from the adipose tissue or dietary fat intake.

Not My 100 Hour Fast Experiment, But Illustrative of My Point Still
Not My 100 Hour Fast Experiment, But Illustrative of My Point Still

As the fast continues, blood sugar levels and insulin drop, glucagon and ketone concentration increase, eventually leading to the body entering a state of ‘nutritional ketosis.’ It’s an altered metabolic state, that shifts the body to use free fatty acids and ketones as its primary fuel source, as opposed to glucose.


Day Two –
Nothing New

The most difficult part of any extended fast is getting to bed at the end of day one. This is so because your body is still used to eating. Afterwards, hunger, lethargy and fatigue all disappear thanks to getting into ketosis.

Day two began as usual. At that point, I had already gone to the retreat.

I begin my mornings with first drinking at least a half a cup of water with a pinch of sea salt in it. This will replenish my electrolytes and prevents the adrenals from pumping out too much cortisol. Increasing your sodium intake is very important during fasting because it would create another stressor to the body and cause tiredness, muscle cramps and headaches.

What to Do During a Fast:

To make time fly past faster, to alleviate hunger and to make the process more enjoyable.

  • Keep your mind busy: most of the time people get hungry because of boredom. Instead of quitting, you would want to do something productive that makes you focus on something else other than the fact that you haven’t eaten nor plan to do so for upcoming days. Read, write, do some paperwork, watch videos or learn a new skill.
  • Go for a walk: very low intensity exercise is very beneficial and advised during fasting. At that rate, you’re burning primarily fat for fuel and will thus make them circulate the blood stream. This reduces hunger and keeps you satiated.
  • Experience it: don’t run away from it or try to make it vanish. Instead, take it as an opportunity to reflect back on the experience and gain reference to how your body reacts to these SHTF type of situations.

At 48 hours in, I was perfectly fine and there were no negative signs or experiences. By that time, I was beginning to look more flat. All of my body had been flushed from its glycogen reserves and I had lost some water weight.

Falling asleep at the second day isn’t nearly as difficult as during the first one. Your body has already become quite ketotic and your mind will have liberated itself from the habit of eating as well. It’s all downhill from here.

Day Three –
New Baseline

Or so I thought. Morning at the 60 hour mark began as usual. I went to the bathroom and looked at my body – I was still looking toned and I definitely hadn’t lost any muscle mass. Funny enough, I seemed to not have lost a lot of fat either. Most of it was water weight but I wasn’t distraught over it.

After a few hours of waking, I had to stand up for about 45 minutes and this caused some mild hypoglycemia. I started to feel slight dizziness and lethargy. What was the cause? I figured it had to do with too low of a sodium intake. To alleviate that, I sat down for a while, relaxed and consumed some salt.

How does it feel to not have eaten for over 60 hours? To be honest, not any different from how you’d normally feel on a ketogenic diet. You’ll have constant energy and are always satiated. I did not even once reach a point where I got any signs of cramps or hunger pains or anything the like. Whenever I did get slightly hungry, I drank some more water and it diminished immediately. The growling of my stomach also became something external as if it originated from outside of my body.

How to Not Get Hungry:

  • Drink more water. To not get dehydrated at the same time and cause an additional stressor, you want to drink more water than usually – more than 8 cups a day. Sparkling water is also a very powerful appetite suppressant. Make sure to add a pinch of salt to it.
  • Drink non-caloric beverages. Green tea and herbal teas have many medicinal properties but they also reduce appetite. Have a cup after waking up and you’ll be satisfied for hours. You would want to wait until you get really hungry and there’s no way out of it before you consume coffee or black tea. You don’t want to become resistant to the effects of caffeine and overdo it – don’t drink more than 2-4 cups of coffee a day.
  • Use apple cider vinegar to stray off hunger once it gets too difficult. get a glass of warm water and add 1-2 teaspoons of apple cider vinegar. Any more than that may have some unwanted consequences, so don’t go overboard.
  • Brushing your teeth is another option.

A Word on Non-Caloric Sweeteners

Avoid diet-sodas or other artificial sweeteners. Despite their non-caloric content they still give rise to insulin, creating a placebo-like fed state.

Day Four –
Nearing the Finish

Day four was when the fun really started. At that point I was in such a deep state of fasting ketosis that I could’ve easily continued not eating for over a week.

In the morning I started coming back from the retreat. It was 7AM and during the night we had hit a blizzard of some sorts. The wind was blowing hard and there was snow everywhere with temperature dropping down to -10°C (14°F). I had a train to catch so I began my march to the station through the storm. It was quite cold even for me but I didn’t feel dreadful about it. Fasting actually bolsters the immune system and makes your body more resilient to physical stressors.

At around the 96 hour mark, I drank a hot glass of water with lemon juice squeezed into it. It tasted quite amazing and definitely stimulated my gut. The reason I did it was to slowly wake up my intestines and make them produce some stomach acid. I didn’t eat anything yet because I still had some business to take care of.

How Was My Strength and Muscle After Fasting for 4 Days

After this I went to the gym to see how fasting had affected my strength and muscle mass. Surprisingly, I didn’t feel or look much different. Of course, I was flat and slightly sluggish but overall I was good. Another reason for this might have been my targeted ketogenic workout shake, which consisted of some whey protein, one tbsp. of MCT oil and a few grams of glucose. This hardly had an impact on my blood sugar levels and still kept me in a fasted state.

Then I did a short little workout, consisting of heavy back squats, muscle-ups and regular pull-ups. It lasted for 30 minutes and I definitely didn’t feel the need to do anything more than that. Striding through that blizzard in the morning had already left a mark on me so there was no reason to push myself further, although I felt I could’ve done so easily.

When the clock was nearing 100 hours, I was already cooking my first meal. Before that, I drank another cup of hot lemon water, followed by a half an avocado, a few almonds and a hard-boiled egg.

Your first meal should be something small and low-glycemic. This will keep you in a semi-fasted state because of the non-existent rise in blood sugar. Carbohydrate refeeding after fasting causes an abrupt weight gain[iii]..

Then, I waited for 30 minutes and continued eating some more ketogenic meals. They included vegetables, some carrots, eggs, pork, cheese with butter and olive oil on top.

The first mouthfuls were quite amazing and I could feel my energy levels rising. During the fast I had a ton of energy and vigor but the zero-calorie policy still leaves some limitations to what you can do physically.

Lessons Learned from a My 100 Hour Fast Experiment

There were a ton of things I found out about my body and self during this short fasting experiment. Given I did it in a meditation retreat where I meditate several times per day, my insight felt even more profound and assuring.

  • Hunger is not you. The feeling you get isn’t a part of yourself, in an objective sense. Instead, it’s simply an urge – a momentary sensation – that occurs due to subjective circumstance – whenever you get dehydrated, bored or reach a certain time window.
  • You don’t need to eat so much. Our body has developed many complex mechanisms that all allow us to survive periods of caloric abstinence. When food intake drops to a zero, we shift gears into a different metabolic state that poses us with a whole set of new physiological conditions.
  • Eating less frequently is more beneficial than doing it more often. For the vast majority of people, intermittent fasting should be a part of their habitual nutritional strategy. It’s an amazing way to empower and bulletproof your health, while saving money, time and mental energy, which you could direct into other more productive and creative channels. The masses eat just because they’re bored.
  • If you can fast, you’re GOOD. Once you condition your body and adapt to it, fasting is very easy and actually enjoyable. The ability to voluntarily abstain from food belongs only to a select few – to those who truly understand the benefits of this practice and have the willpower to rise above their immediate urges to give in to hunger and boredom. A discipline of Agogeans.
  • Periodic abstinence leaves you more nourished afterwards. I did not only abstain from calories but also fasted from the other volatile stimuli of modern life. Doing this at a meditation retreat was a great decision because I was in an environment where I had nothing else to do but contemplate and enquire my body. There was boredom which I urged to escape from – it was actually more difficult than not eating – but I purposefully came faced and accepted it. It was supposed to be a time for rest and recovery so that I could charge ahead in life with greater speed. Afterwards, my physiology and nervous system had rejuvenated themselves and I was more nourished than before.

Concluding Remarks

Doing intermittent fasting in some shape or form is the surest yet simplest way to improve your health, increase your body’s physiological potency and make you more rejuvenated.

Everyone should fast for at least 3-5 days 2-3 times per year. It’s the least you can do to protect yourself against disease and clear your life from the clutter that’s distracting and slowing you down.

The best and healthiest way to do intermittent fasting is in combination with the ketogenic diet. Physiologically, the two are almost identical and thus a match made in heaven. If you’re eating keto already, then it takes less time for your body to adapt to the zero-calorie policy and tap into your prime-primal state.

To learn more about the art of fasting and ketosis, get my KETO // IF program that combines two of the most self-sufficing and empowering nutritional strategies into a whole. You’ll also get a ketogenic meal plan to get started and a fast formula.





[iii] Bloom WL: Inhibition of salt excretion by carbohydrate. Arch Intern Med 1962 Jan; 109:80-86 48.

Veverbrants E, Arky RA: Effects of fasting and refeedingI. Studies on sodium, potassiulm and water excretion on a constant electrolyte and fluid intake. J Clin Endocrinol 1969 Jan; 29:55-62 49.

Botulter PR, Hoffman RS, Arky RA: Pattern of sodiuLm excretion accompanying starvation. Metabolism 1973 May; 22: 675-683

5 Comments on “My 100 Hour Fast Experiment

      1. hey thanks for the reply!!
        i found it cause i was googling somethin about OMAD and keto, and this was some of the main options.
        man, i wanna try right away OMAD with keto…. im not into keto state, but im overweight and i need to drop pounds fast because of a knee problem and energy levels (below the floor). i have a kid and another coming, i cant play with her cause i cant be on the floor too much.
        i wanna start omad and keto right away and some resistance training. pls give me some advice 🙂

        1. That’s great, I love OMAD as well. I’ve been doing it for several months now and I’ve never felt better or stronger. In the best shape of my life right now. Doing OMAD on keto is an amazing way to drop some pounds and improve your eneergy levels.

          The best advice I can give you is to consider my coaching services. I offer nutrition, training and holistic health advice to people. It would enable me to give you an individualized plan that meets your specific goals and conditions. If you’re interested, then send me an e-mail at:


  1. “workout shake, which consisted of some whey protein, one tbsp. of MCT oil and a few grams of glucose”. That is not fasting. You said you had nothing to eat or drink except water and tea.

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