Mon. Jun 24th, 2024

Observations from a 48 hour fast

6 min read
48 hour water fast

Recently I completed a 48-hour water fast. I started this fast after my evening meal on a Sunday night and consumed only water for the next 48 hours, ending the fast when I commenced eating again on Tuesday evening.

The benefits of fasting for an extended period of fasting are numerous including;

Inflammation reduction, Improved blood sugar levels. cellular repair and slowing of aging

There are also some drawbacks to a 48 hour fast including;

Hunger, dizziness, insomnia and exhaustion. If you are considering an extended fast you should be mindful of all these factors that you may experience.

The Fast

I began my fast at 7pm on Sunday evening. My weekly schedule was unchanged meaning I had a full day at work both Monday and Tuesday and was planning to continue my normal routine including running both days.

Monday started with an early start and my regular run, skipping my regular coffee in the morning was the first challenge post run. While I didn’t necessarily miss the coffee, it was the habit of my morning coffee that became the first challenge.

Increasing my intake of water was an obvious strategy to get through the 48-hour period. Staying hydrated is important during longer fasts to suppress hunger and avoid the drawbacks.

The challenge of this 48-hour fast came during the morning when I became very hungry around breakfast and lunchtime periods. I regularly complete intermittent fasting of 16:8 hours, meaning I don’t always have breakfast however in this time I felt considerably hungry around 8am and then again between 11-11:30am after 16 hours of fasting. This was my first real sight of the real psychology of eating. This period of hunger didn’t last particularly long however on both these occasions I was extremely hungry. I was in the infancy of this fast and the hunger took me by surprise. Once these periods of hunger past I generally felt quite comfortable through the first day of the fast.

On the Monday evening I felt good. I had drunk approx. 2 litres of water through the day but overall felt quite good. While the hunger wasn’t too bad on the first evening I quickly became tired and went to sleep around 8:30pm.

The biggest challenge I experienced through this fast was the sleep I experienced on the Monday nights. After falling to sleep quite quickly I woke up around 11:30pm and then struggled to sleep again for the entire night. Tossing and turning until morning. For this reason I skipped my Tuesday morning run for an extra 90 minutes sleep.

On waking I had a throbbing headache and felt quite flat due to the poor nights sleep I experienced. I drank some water and after an hour the headache had mostly passed. 

Tuesday morning, now 36 hours into my fast and I felt quite good. Hunger came and passed over the morning without too much concern however I became very hungry again around 1pm with 6 hours to go. Further highlighting the psychology we experience around regular meals times. The habit of eating at the same times each day can be almost paralysing to some.

The Tuesday afternoon I felt relatively comfortable. Although hunger was building I was in the final stages of the fast and this was a motivating time. I came home around 4pm and decided to go for a short run. I had missed my morning run due to my poor nights sleep and it was a good opportunity to fill in some of the final hours of my fast. This run felt extremely difficult to begin with, my energy levels were understandably low and running even for a short period didn’t come easy.

The last two hours of the fast were quite difficult. While the hunger and drawbacks weren’t extreme I felt like I was treading water, waiting for the fast to end. This happened at 7pm Tuesday evening and I was satisfied with overall how I felt throughout the fast.

Biggest Observations

  • Eating is highly psychological.

While hunger came and went throughout the two days, the most challenging periods of hunger were experienced almost always around my regular meal times. While there is no reason why I should’ve felt hungrier around these times I certainly did and they were challenging at times to get through. We have a psychological attachment to eating at out normal meal times, if we don’t eat these times the hunger experienced will pass quite quickly.

  • Sleep is more important than food

Quite clearly the human body needs both food and sleep to be at it’s best, but you’ll get further on no food then you will on no sleep.

While the affects of hunger come and go sleep deprivation is much more constant. When you have a very poor night’s sleep there is no where to hide the symptoms. You are tired until you sleep again. While the effects of hunger will come and go and be much easier to suppress.

  • Fasting is like running a marathon

The affects of an extended fast is very similar to the mental and physical stress experienced when running a marathon. When you run a marathon it becomes increasingly difficult the further you get and then this feeling plateaus slightly. During this time there are many ups’ and downs along the way. Nearing the finish it becomes a very real mental challenge to continue.

It is often said the last 10km of a marathon is like nothing else. I’d say the last two hours of a 48 hour fast is similar. In my experience of both, you can see and feel the finish line in the near distance but must see out the final moments before you get to a satisfying finish line. In a marathon you can’t run down the clock like in other sports, you must run to the finish. While you are essentially running down the clock when you finish a fast it has a very similar feeling.


At the end of my fast I was able to eat again and was mindful not to eat too much or too much carb rich foods to spike my blood sugar back into action. I ate a light meal and still felt relatively flat. After 24 hours again of regular eating my energy levels had returned, and I felt completely refreshed.

Over the course of the 48 hours I lost 1.9Kg. As a 72Kg male my aim wasn’t to lose weight. My aim is to improve my overall health and believe regular fasting will help me on this path. Over the course of the next week all of this weight has returned.

While a 48-hour water fast came with many challenges, most I was prepared for. I certainly didn’t expect it to be easy and it wasn’t. Overall it was easier than I expected, I was surprised how well I felt during the last 12 hours of the fast.

In the future I intend to use extended fasting periods as part of my health practises. My goal moving forward is to complete a 24 hour fast weekly or fortnightly as well as regular intermittent fasting and a monthly 48 hour fast. This may vary depending on where I am in my training cycle. I may not complete a fast greater than 24 hours within four weeks of a marathon or ultra I am entered but fasting will be part of my health practise moving forward.

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