I’m writing this as I just finished my 60 hour fasting (2.5 days) and had my light keto-breakfast. On waking up this morning I didn’t feel much hungry, it felt more like emptiness rather than hunger. After having my breakfast 30 minutes ago, I feel fulfilled. Nothing spiritual, just calm.

Reasoning

aka why did I do it

I was reading Tools of Titans book and it brought again the topic of fasting as something that many people could benefit of. From all the benefits I could find and somehow proof-check, main ones were:

• Try ketosis state
• Get mind clarity and be able to focus earlier
• Cancer prophylactic
• See if that would influence my weight

Results - Ketosis

Based on my urine test I got into mild ketosis in less than 18 hours, and full ketosis (~4-8 mmol/L) in 36 hours. Then it stayed at that level for the rest of the fasting.

Results - Mind clarity

Normally I don’t have problems with focus and mind clarity. Also I don’t consume caffeine or any other substances to boost my productivity. The only thing I do more or less constantly is a 19 minute power-nap somewhere after lunch.

During first day of fasting I felt a bit exhausted at around 11am, and also did 2 longer power-naps during that day. Other than that I was pretty active and doing all the usual stuff.

During my second day I went to work. For the entire day I was much less hungry than the first day, but I felt a bit fuzzy. That wasn’t bothering me at all, I just fell a bit different. Also I was able to focus and do productive work (as on any usual day).

As a conclusion I didn’t get more clarity or more mental power (at least not noticeable).

Results - Weight change

In the last 3 years my weight varied between 61 and 66kg (135-145lb). Before fasting my weight was relatively stable at 65kg (143lb) for the last 2 months. My height is 183cm (6 feet) so at 61kg I’m considered underweight, anything above goes into the “Normal” weight category.

During fasting my weight went down by 3kg (6lb):

• 65.7kg (144.8lb) - morning before fasting
• 65.6kg - first morning of fasting
• 64.2kg - second morning of fasting
• 62.8kg (138.4lb) - last morning of fasting

Most of this weight should be water (in case you’re wandering if all of that was fat).

The plan

The best part about Tools of Titans book was that it had instruction on how to have an easier fast. It included a warning to not fast on distiled water only as it has a bunch of drawbacks (like cramps). Based on that and some more reading my plan was:

• Have a low-carb dinner in the last evening before fasting
• Fast for 3 days (which I cut to 2.5 later, aka 60 hours)
• Sleep as much as possible (which didn’t work for me, I actually slept the same as usual - 8.5 hours)
• Consume up to 60g (4 tbsp) of MCT oil per day until in ketosis
• Consume lots of mineral water (or add salt to water)
• On first morning of fasting - get out for a 4 hour walk (no exercise)
• Measure ketones levels few times a day to check for ketosis (and make sure I don’t get into ketoacidosis)

Timeline

This is a long section, so feel free to skip to the conclusion

Wednesday Lunch time

Had a low-carb diet without any starches or gluten. Mostly greens, fish and oil.

Wednesday Dinner (8pm)

Has a low-carb diet. Mostly greens, courgete, a bit of quinoa and chicken. This was my last proper meal for the entirety of fasting.

Wednesday Night:

Slept between 11:30 pm and 8am.

Thursday breakfast (9am)

Wasn’t really hungry (I often skip breakfast). Gulped 30g (2 tbsp) of MCT oil. Interestingly I got a diarrhea after about 1 hour (could have been the previous day food, or the oil). This was quite unfortunate as I wasn’t excited to loose minerals, but at the same time I didn’t want to stop the experiment. Ketone strips were showing that I have 0 ketones.

Thursday post-breakfast (10am-2pm)

I left home and went for a 3-4 hour walk. I effortlessly cycled to a park and spent the rest of the time there. At some point (around 11am) I felt like I have lack of energy, but it went away pretty quickly. I probably drunk about 3L (6 pints) of water (50% mineral/50% filtered).

Thursday lunch (2pm)

This time I made some rooibos tea and poured 15g (1 tbsp) of MCT oil. It was pretty warm (but not hot). It was much more pleasant to drink it this way. Also my body seemed to accept it.

Thursday dinner (6pm)

I tested my ketones and it was showing between 1.5 and 4 mmol/L. Supposedly I was in ketosis (supposedly because it’s a urine test that may be not accurate). I had my third rooibos tea with 15g (1 tbsp) of MCT oil. I was having some food cravings, but not too much.

Thursday night

My sleep was a bit shorter (7.5h), but it was enough for me. Also I fell asleep mostly instantly (usually it takes me 15-30 mins).

Another difference was that I was feeling cold. Normally during summer I always feel hot even without a blanket. It was 74F (23C) in the house. I always feel hot down to 72F (22C).

Friday day

As I thought that I’m in ketosis, I skipped the MCT oil. In fact I felt less hungry for the entire day compared to previous day. I was still drinking a lot of water (probably double my usual).

I went to work at around 8am and came home at 6pm. Given that I didn’t have lunch-break, and only a 19 min power-nap, I definitely over-worked. But I didn’t feel exhausted (which normally happens if I work for 10 hours straight).

I felt a little dizzy during the day, but that didn’t interfere with my activities. I tested my ketones levels during the day at it would be consistently somewhere between 4 and 8mmol/L (closer to 4).

Friday night

I again felt pretty sleepy at around 10pm, but it somehow went away and I got into bed at around 11pm. Apparently I felt asleep very fast (based on the Sleep Cycle app).

But I was dreaming stuff as I woke up at 1am thinking some crazy stuff (mostly about ketosis diet). I drunk some water and went to sleep again, only to wake up again at 4am. From 4am to 7am I had 3 or 4 times when I would be semi-conscious, check if sun has risen, and go back to sleep knowing that if I don’t sleep, I’ll feel bad next day.

Overall it felt like a bad sleep, but I wasn’t sleepy during the day.

Saturday morning

I was eager to finish my fasting and start eating, even though I would feel extremely hungry. I had a full-fat greek yogurt with some berries and nuts for breakfast.

My ketones level were now closer to 8mmol/L, but that could be because I didn’t have much urine that morning.

After that I went to cycle for 10 minutes and the uphill that would normally be a bit hard, felt exhausting this time. Immediately after starting eating my thirst stopped, and I had a single cup of water for first half of the day.

Saturday day

During the day I had 3 more foods, but I tried to maintain my ketosis by following “Keto maintain” diet from Lifesum app. I wanted initially to choose the foods by myself, but Lifesum has a very convenient feature of proposing you a diet and then building a grocery list that it felt too good to not use it.

By evening my ketones also seem to have gone down to 2-4mmol/L but didn’t vanish completely, which means that either I still have a bunch of ketones left in blood, or the keto diet is working.

Conclusion

All in all it was an interesting experience, and I’m looking forward to see how fast I’ll gain back all the weight, and if it will change my hunger levels and general health.

Also I was pleasantly surprised that it wasn’t too hard to stay on the diet and it didn’t affect my daily routine too much.

I would probably do it once every 6 months to as a prophylactic, but not more often as it wasn’t the most pleasant experience.

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