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My experience with a 5-day fast

My experience with a 5-day fast


Why 5 days water fasting? 

My goal is to test all different methods of (intermittent) fasting. Normally I drink a Bulletproof coffee in the morning (Bulletproof Intermittent Fasting) and wait till 2 pm to eat. But many times I don't eat at all until 2 pm.

I was inspired to do a 5-day fast after reading Tools of Titans by Tim Ferriss, chapter Dominic D'Agostino. There Dominic D'Agostino introduces the idea of a 'purge fast': 'If you don't have cancer and you do a therapeutic fast 1 to 3 times per year, you could purge any precancerous cells that may be living in your body' (Tools of Titans page 24). Tim Ferriss now aims for a 3-day fast once per month and a 5-7 day fast once per quarter.

The longer the fast, the deeper the cleansing of your body. There is scientific evidence that suggests that fasting for 3 days or longer can effectively 'reboot' your immune system. When you are fasting your body comes in a renewal modus. It starts to cleanse itself and makes it ready for survival. When fasting, your body switches from glucose to fat as the primal fuel source. Fat is turned into ketones. When this happens, you are in ketosis.

In this state your body starts all kind of interesting processes:

  • Enhances recovery: Repair only occurs when you fast and takes some time to really get going. Autophagy (=self-eating: recycling of cell structures and proteins), for instance, takes at least 24 hours of fasting to really get started. By fasting for longer periods, more repair mechanisms become active and continue working until you break the fast. 
  • Reduces inflammation: Accumulation of damage and waste is an inflammatory signal. Your body repairs damage and clears away waste while fasting, thereby reducing inflammatory signals.
  • Improves blood values: During periods of continuous feeding, your body can get overwhelmed by incoming nutrients from food and may not have time to properly process them. This is reflected in your blood nutrient and hormone levels. By fasting for some time, your body can deal with the backlog of unprocessed nutrients and rebalance hormone levels, improving e.g. blood glucose and insulin sensitivity.
  • Quick weight loss: During a prolonged fast, your body draws upon stored fats to supply energy. By burning off fat stores and rebalancing hunger hormones, it becomes easier to adhere to dietary adjustments to achieve permanent weight loss after the fast. Fasting is an easy way to lose weight quickly and lose body fat.
  • More/better mitochondria: Repair of damage and clearing out waste that occurs during fasting also includes the repair and clearing of damaged mitochondria. Prolonged fasting (multiple days) further stimulates the growth of NEW mitochondria. Together these benefits of fasting make your existing mitochondria produce more energy.
  • Improves sleep: Your brain contains a lot of mitochondria and by improving the quality of your mitochondria, more energy can be generated in the brain. The brain clears away waste while you sleep, which requires a lot of energy to do properly. Having a healthy, clean brain with lots of energy improves all aspects of mental performance, including your sleep cycle and regulation. 

 Benefits of Fasting

The different fasting methods and the benefits of fasting (design: Dagmar Bouwer).

Is 5-day water fasting the same as the Starvation Diet?

It is a question that I was asked quite often when during this experiment. The starvation diet has a negative connotation and I associate it with fat gain instead of fat loss. This can be explained by the fact that on a starvation diet you still eat, but significantly fewer calories than your body needs. Your body's metabolism will slow down to adapt to the new (low) amount of calories. This causes most people to feel miserable structurally. They lack the energy to perform at their normal level. When you start to eat normally again, by consuming more calories, it takes time for your body's metabolism to adjust. This means that you get more calories in than you need. The result is that you risk adding more weight than before you started the starvation diet.

However, when you do a 5-day fast, your basic metabolic rate is 10% higher after the fourth day. The body doesn't shut down but uses your fat reserves as a fuel source instead. And most people have plenty of fat to use for fuel! That means that fasting is a more effective strategy if you want to lose weight. 

What protocol did I use for my 5-day water fast?

I started with the protocol described by Tim Ferriss. To stimulate ketosis, I ate every 4 hours one tablespoon of Octane Oil or one serving of exogenous ketones (Ketosports). That means that on day one I consumed two tbsp Octane oil and two servings of Ketocana. I also took 1 serving of Natural Stacks BCAAs to prevent muscle loss. If you are not in full ketosis, your body starts to burn your muscles for fuel. And that is not what you want. I did the same on day 2.

There are thought leaders like Rhonda Patrick who claim that this is not a real fast. They say that the only fast is a water fast, i.e. you should only drink water, nothing else. That's why I decided to switch to just water on the third day. I started the day with a glass of water with some Keltic sea salt in it. The rest of the day I drunk Pellegrino. Just because I like that taste. I must admit that I didn't skip my espresso. Leaving that out was too much......

What did I measure during my 5-day water fasting?

I measured the ketones and glucose with the Abbott Freestyle Precision. I was able to measure both with just one prick in my finger. Ketone strips are expensive though. They cost €3-4 a piece. That's why Ketonix breath analyzer is a cheaper alternative if you want to test it continuously. I forgot to measure the first two days with the Ketonix.

I used the Oura ring to measure my sleep, heart rate variability, and readiness. Readiness is an indicator of how well you can perform at your best both mentally and physically. It is generated using all of the sensor data, physiological signals, sleep and activity patterns that are monitored by ŌURA.

8 am day 1:

  • Weight 95,3 kg
  • Ketones: 0.1 mmol/l
  • Glucose: 5,5 mmol/l
  • Heart rate variability (HRV): 32
  • Sleep:76%
  • Readiness: 78

I didn't sleep well. Maybe because I wasn't looking forward to this experiment :-). However, this day was quite easy. Only a bit hungry at 6 pm when I normally eat a big meal.

8 am day 2:

  • Weight: 92,1 kg
  • Ketones: 0,7 mmol/l
  • Glucose: 5,9 mmol/l
  • Heart rate variability (HRV): 39
  • Sleep: 82%
  • Readiness: 91

Sleep was better, but still not that well. Mentally clear. I was not feeling tired. I was very hungry at the end of the day. The level of ketones was exactly what Tim Ferris aimed for in his protocol after day 1.

8 am day 3:

  • Weight: 91,0 kg
  • Ketones: 0,8 mmol/l
  • Ketonix: 3.2 ppm
  • Glucose: 4,9 mmol/l
  • Heart rate variability (HRV): 39
  • Sleep 90%
  • Readiness: 92

Woke up early at 6 am. I slept well. In the morning I felt Ok, the afternoon was hard. I felt hungry and didn't have much energy.

8 am day 4:

  • Weight: 90,3 kg
  • Ketones: 2,0 mmol/l
  • Ketonix: 9.4 ppm
  • Glucose: 3,6 mmol/l
  • Heart rate variability (HRV): 45
  • Sleep: 94%
  • Readiness 96

I woke up at 4.30 AM and felt stressed. Tried to sleep for another 1,5 hour. Felt miserable. After a glass of warm water with Keltic sea salt, I felt much better. My mental performance was perfect till around 4 pm. After that, I felt tired without much energy.

8 am day 5:

  • Weight: 90,1 kg
  • Ketones: 2,6 mmol/l
  • Ketonix: 15 ppm
  • Glucose: 3,8 mmol/l
  • Heart rate variability (HRV): 48
  • Sleep: 88%
  • Readiness: 90

I woke up at 6 am. My body felt very stressed. After a glass of warm water with Keltic sea salt, I felt much better. The rest of the day was perfect. I was mentally sharp and didn't feel tired. I finally got the experience I was aiming for!
I broke my fast with a delicious meal of Sushi. 

What are my conclusions?

My insights after this experiment:

  1. I started small. I did a 2-day fast 6 weeks ago. This helped me to get a mindset for not eating for a longer period.
  2. I am still able to suffer. The first four days were no fun and it took a lot of willpower to continue. I think it is partly character (willpower) and partly training. In my youth, we did a lot of endurance sports like cycling and mountain climbing. In the mountains there is no escape, you continue otherwise you die (or be rescued by a helicopter). I presume that this kind of mental training is helpful for the rest of your life.
  3. Fasting causes stress. If you are prone to stress (as I am because of a side effect of the use of Lariam 17 years ago) that is no fun. The stress was building up till the ketosis was deep enough. So be warned: if you are stressed this 5-day fast may not be a good idea to do. Plan ahead so that your week is not fully booked with important meetings and presentations!
  4. The transition into ketosis makes you feel tired. I kept working for 10 hours a day. That may be not have been a good idea. Next time I better try to make some changes to my agenda to make it easier.
  5. Start a fast when you are already in ketosis. Fasting is easier if you have made the transition to a ketogenic diet. When you have up-regulated the fat-burning systems and down-regulated the reliance on glucose, many of the other issues I experienced tend to go away: cortisol levels out, muscle protein is spared, hunger subsides naturally, and energy is steady.
  6. My sleep, readiness and heart rate variability improved. That means that positive things were happening inside me!
  7. It was an easy way to lose weight quickly. I lost 5 kg and gained back 2,5 kg in the days after starting eating again. I calculated that I have lost 1,5 kg body fat. 
  8. It saved me a lot of time! I didn't have to do groceries, cooking, tidying the kitchen, etc. I was amazed at how much time extra I had.  
  9. Accountability helps a lot. I shared my experiment on all social media so there was no way back. 
  10. There are tough moments. I coped with them by doing all kind of activities that distracted my thoughts like going for a hike.
  11. Your digestion comes to a halt. It took me some time to get it going again. I accelerated this process by eating Natural Stacks Prebiotic+ and Natural Calm magnesium. Prebiotic+ contains resistant starch and helps a lot if you have problems with your digestion. But be aware, my wife had the opposite experience. Within 30 minutes after starting her first meal she had to run for the toilet.
  12. Drinking a lot of water helps to cope with the hunger. In fact, feeling hungry can be caused by the need for water. Also, drinking water helps you to get rid of the toxins that are released by burning fat. However, don't drink too much because it also depletes your minerals. I drunk 3-4 liters of water per day and added some salt to prevent depletion.
  13. It helps to start your fast with a brisk walk or cycling. It depletes your glycogen stores in your muscles which stimulate the transition to fat burning.
  14. Fasting together is more fun. It is easier to be part of a group so that you can help each other. Next time I will create a group so that you can join us!

Would I do it again? Yes, I will. But next time I will make sure that I take these learnings into account so that it will be a lot easier!



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