I did a 5 day fast on the ketogenic diet

September 30, 2020 by No Comments

For this first article on long fasting on a ketogenic diet, I will mainly share with you my experience, which I more or less documented as I went along. Here, no theory, no studies, no data: I will be my field of experimentation, and my source of data! It was a big first for me, who had never done a classic fast, and if that interests you, I’ll tell you a little about it.

fast on the ketogenic diet

Having never fasted in my life (apart from intermittent fasting or max 24 hours), I did not understand what to expect, or what my body was capable of. Total unknown zone. But despite everything, I thought to myself that, if the theory is true, if the ketogenic really mimics the effects of fasting, then I must be able to do it. And with nearly 5 years of ketogenic under my belt, I assumed that my adaptation was strong enough to show it.

Ultimately, that’s the whole point of this experiment: to 
validate or invalidate the hypothesis that a ketogenic metabolism is ideal for fasting !


For this very first fast, I wanted to be in optimal conditions. So, I programmed:

  • 5 full days ,
  • water fasting: therefore water at will and some food supplements such as magnesium, sodium, potassium.
  • Period of almost non-activity: over these 5 days, I only worked in the store twice for 3-4 hours, at a calm pace. I was lucky; it fell like that by chance, and suddenly I jumped at the opportunity to organize this 5-day fast.
  • no gym, no workout
  • walking periods of 30-60mn, 2 to 3 times a day
  • with followed by classic markers in ketogenic such as glycemia, ketonemia, energy, sleep, mood, physical sensations.
experience keto diet

Some would say that 5 days is not strictly a “long fast”. But for me, 5 days is being not bad, and for a first experience, I frankly did not want to push anymore. And even if I wanted, my schedule of obligations and work did not lend itself to it. 
And if you have already followed my dry protocol, you already know that the YOUNGER is a synonym of REST for me!



Blood glucose : 4.0 mmol / L Ketonemia: 2.8 mmol / L

I would add in passing that I took all my blood sugar and ketonemia measurements with the GK DUAL from Swiss Point of Care, and checked (when I had doubts, as on day 4) with a counter-test on a keto- mojo. Each time, my values ​​were roughly the same, so we can assume that the values ​​given are reliable.

I had planned to go to train, instead I had to go to work urgently. same, same . 
Strictly , I was not hungry. It was actually more frustrating because of the day I wanted to eat, more to take a break and eat something that makes me happy than really because I needed it. Suddenly, a little tea and the urge is over. 
I had energy normally. Apart from those few hours in the morning at the store, the rest of the time I worked rather sitting (unfortunately). I added a 45-minute walk in the evening. 
Note that in the evening when I went to bed, I had tingling in my hands and forearms. It had never happened to me before.

DAY # 2

I slept badly. I don’t know if it’s fasting or rather, that I drank too much tea to make up for it during the day (even deheated, there is ALWAYS some theine left, let’s face it!)

Glucose: 3.6 mmol / L
Acetone anemia: 3.6 mmol / L

it is normal for blood sugar to drop and for ketonemia to rise during a fast… But it happened sooner than I expected!

I was more tired, but also because I had slept really badly! I was a little hungry in the morning, and a few times during the day, but like 5 out of 10 hungry, nothing crazy. I passed it with tea or water. 
No sport, 3 x 40mn walking during the day, lots of rest. 
I had tingling in my hands and arms too, but less than the day before.

There were many told me: you will see the first 3 days is a nightmare, it’s very hard, etc, etc. Honestly, I think it would have been “difficult” if I had to work for sure. But there, being at rest, I found it easy.

The hypothesis is confirmed: ketosis being present from the first hours of the young, and the body being used to using stored fat, fasting is easy and doable. From an evolutionary perspective, it makes perfect sense. Our ancestors could hold long periods of fasting while waiting for the next “catch” of the hunt. They were maybe a little less perennial, but it was metabolically viable!

DAY # 3

I slept very well (I had been careful with the tea) (so that was it!)

Blood sugar: 3.6 mmol / L 
Ketonemia: 4.7 mmol / L

Note that, as I explained to you, blood sugar is lower than usual , and especially ketonemia is climbing rather sharply! Preventive mechanism according to the hypotheses of Peter Attia.

I took several walks during the day; I felt good with the energy to walk, but not to kill myself in the gym (which I did not do). I worked 4 hours in the afternoon (at a very chill pace), and everything went very well. 
Small tingling, always, in the hands / wrists / forearms. And in the evening a little in the feet.

I feel good, very calm inside, from an emotional point of view. It feels good to let go a bit with all the mentalization of food. There isn’t any, so in fact, we don’t think about it anymore! 
I’m not hungry, I don’t find it difficult at all, I just miss the food if I walk by or are told about it!

From a digestive point of view, excuse me for the glamor, but I have very little in my intestines and yet I’m still emptying a little (it’s liquid and strangely it’s… GREEN!) (I don’t understand nothing ^^)

DAY # 4

I still slept badly enough, I worked late on my computer, and WITHOUT my blue-blockers. that will teach me!

Blood sugar : 3.6 mmol / L Ketonemia: 4.9 mmol / L

I took a walk in the morning, one at noon, and then I joined my boyfriend in the countryside. 
I had a pleasant laugh because this episode of fasting literally made him ENRAGE! He kept telling me (I loved the formula): “no, but in fact fasting is a non-event for you! You are exactly the same as usual!  And it’s true that apart from not going to the gym, on day 4 I was great, with fairly constant energy.

I had a wonderful day, with maybe a little nausea / dizziness but which passed with salt and magnesium. 
Yes, because I forgot to tell you that regarding minerals, I closely monitored my intake, and slightly increased them:

  • magnesium bisglycinate: 500mg / day
  • sodium: 5-6g
  • potassium citrate: 1000mg / day

I have no more tingling in my hands; I am better and more calm, and my mood is superb and remarkably stable. I think I am someone who tends to over-intellectualize food, and therefore this break time is doing me a lot of good …

DAY # 5

I slept very well (but it was cool, and no screen the night before).

Blood sugar : 3.2 mmol / L Ketonemia: very weird, I drop to 1.9 mmol / L

I had trouble interpreting this data. After a period of fasting, does the body absorb ketones on a sped up basis? Or, conversely, does the body’s production adjust?

On these questions, I went for a walk of over 2 hours in the forest (my guy was still enraged to see me frolic at the same pace as usual). Back from the ride, the ketonemia is at 1.6 mmol / L, which could confirm the hypothesis of the sped up use of ketones. But it really remains a vague hypothesis, I’m not at all sure of myself.

Later that day, around 4 p.m. my ketonemia returned to 4.5 mmol / L. I admit you still wonder about this episode. We’ll see that at the next youngster! (if some have interpretation assumptions, go ahead!)

From 2 p.m. to 4:30 p.m., I was not in good shape at all. I had less energy, a stroke of fatigue, my head spinning. Around 4 p.m. I took some salt and magnesium again. At 5pm, I have a live on YouTube with you! Panic before starting, poor connection, technical problems, poor start, etc. Rise in stress. And then, very good time with you at the end of the live, my energy had returned to normal!

I broke the fast that evening at 9 p.m., which brings me 5 full days. I could have pushed the next morning, but for technical reasons, because the next day I had to get up early and go to work on the hats of wheels, I preferred to eat the night before. We will see for the next one for improvements (I have lots of test ideas in fact !!)

Contrary to my expectations, I didn’t start with bone broth. I just ate meat cooked in beef fat. Unlike usual, I really ate it VERY slowly, and maybe that’s what made the difference, but I had no problem with digestion. I was VERY hot when I was eating… Big increase in my internal thermostat. It was eloquent!

Read our article on Custom Keto Diet.Com Reviews by Rachel Roberts


  • So I would say that my test is conclusive and that a ketogenic metabolism has a lot more facilities for fasting. Because he already produces ketones, because he’s already used to using them, because he’s already used to burning stored fat, he can fast without a problem. There are even people that I haven’t told I am fasting to, around my community and at work, and no one has noticed that I am different or look tired.
  • The fact that I got a lot of rest made this first experience. However, I am quite convinced that a metabolism accustomed to fasting over long periods of time is also capable of moderate activity, work, and even training. It is logical, when there was no more food, it was necessary at some point that our ancestors returned to hunt to find some !! 
    On my next experience, I will tell you about it, I know ​​a protocol to introduce!! stay tuned …
  • I was not hungry, I just had, sometimes, the desire to eat, because I like it, and / or because they put me under the nose. But it went quickly! However, the following week, I am a little more hungry than usual. It was not obvious, but still notable. I didn’t regulate; I eat more, period.
  • Interesting thing to note too: I thought fasting would cut off my libido, and in fact not at all. From day 1 to day 5, nothing has changed on this point. 
  • I had real emotional rest, relaxation, a kind of detachment that I have rarely in my life. The meditations were easier and deeper. I would even say that I found myself several times, outside of meditation, in a meditative state . (While this is not very usual for me).
  • On the level of weight loss, I voluntarily decided not to be interested in it, because it is not the subject of the experiment. So I couldn’t tell you how much weight I lost. The physical observation was interesting. During the fast, apart from my stomach, which was naturally flatter (since it was empty), nothing changed. It was during the following weeks that my physique really changed. I was noticeably drier. Some of you saw it, and that change lasted. To make the experience interesting, I weighed myself BEFORE this first kid, and then I weighed myself. am re-weighed exactly one month later. (I invented nothing eh, I had read that the distinct changes after a long fast were to be observed over a month!).Interestingly enough, my weight is exactly the same. I was 55.1kg before my fast, and a month later I’m 54.7kg.
  • So nothing has changed. Strangely, my physique is different. Difficult to analyze because the changes are fine. My entourage saw it and pointed it out to me, I saw it too, I have less abdominal fat (which is my “preferential” storage area: not that it is me who “prefers”, but my body which would have a little inclination to come and store in this place !!).
  • I am trying to get closer to a room that could provide me with a reliable body fat analysis (in-body or dex-scan type), which would allow me to do a real fat mass analysis before and after the young. It’s in progress have also made the same observation several times for intermittent fasting, for myself and also for my coaching clients: at the moment, nothing seems to change drastically. The changes are more visible during weeks 2 and 3 (if we consider the entire fasting period as a single “week 1”.) Because you know, in my dry protocol, I advise you to do short periods of 1 to 2 weeks maximum!


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