24 Hours Without Food: My Eye-Opening Journey into Water-Only Fasting

Published on 5th of March
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For about a decade now, I’ve had an item on my bucket list which doesn’t require much effort. Trying water-only fasting. In February of 2024, my friend Oliver started a group fasting challenge, so the time had come and I gave it a try. Here’s what happened.

🤔 Why Fasting?

People around me have been doing it occasionally since I was a kid. I never really thought much about it, and when I asked them why they did it, I always got the answer that they were either trying to lose weight or trying to detox their bodies. And there were reports of perceived success afterwards, and people regularly repeated their fasting efforts. So it can’t be completely foolish to stop eating for a while, can it?

People who are members of the Muslim community and were also friends or acquaintances of me, answered my questions during their Ramadan months, which I found highly interesting. I’m neither Muslim, Christian, or a member of any other religion, but many of them seemed to have some type of ritual surrounding fasting. That caught my attention as well.

As you might be aware, I have been putting emphasis on living a healthy lifestyle so I can be a resilient and supportive father and husband, and reach my athletic goals, too. I’m doing daily endurance training, strength workouts, breathing exercises, eating healthy and avoiding animal products, reducing screen time, and I’ve given up smoking and alcohol. All of it has helped the cause, so maybe regular fasting will further it even more?

The other big reason for me to try this, is that I’m aware that about 800 million people worldwide suffer daily from serious hunger. I’m so privileged that I’ve never really felt the way they felt. I’m sure it helps building empathy and connecting humankind to share the same emotional experiences and might direct my future actions more towards helping those in need.

🫵 Explain the Rules!

Just water?
Just water?

As a first-timer, you should obviously take things slow. As far as I’m aware there are no serious physicians who would ever recommend doing water-only fasting, since from a health-perspective, there is no hard evidence for any benefits except the fat-loss – naturally. On the contrary, it can be dangerous. The hospitalization rates go up during the traditional fasting rituals of the major religions, so you need to be careful. But how?

There are many types of fasting. I’ve chosen the standard water-only version and take it easy with just 24 hours for now. A huge advantage is that I’m married to a medical doctor who knows a bunch about this.

Water-only doesn’t really mean water-only. There are exceptions which are widely regarded as “okay”, and those are usually salt – a pinch of it added to the water helps with replenishing electrolytes –, and a squeeze of lemon juice. Some say this helps keep the pH of the body stable, but I have to admit I’m not entirely sure why exactly this counts more than all the other health markers which are also suffering when we’re removing food intake in general.

What’s often considered to not be okay, weirdly, is brushing your teeth using standard toothpaste. The reasoning here is that the sweetness and flavor might cause the unwanted insulin peak, messing up the autophagy state the body is in, and therefore break the fast, especially when swallowed.

I decided to give this a go on Sunday, February 11th, 2024. Start at 7:00 PM after having dinner.

📝 What I Experienced

That day I came out of a weekend getaway at the sea, where I made use of the opportunity to go for a 32k long run and a bunch of time spent in the sauna of the place. Lots of calories and water lost. Throughout the rest of the day I tried hard to replenish them and finally succeeded by making a huge wholegrain vegan pizza with lots of different veggies and not forgetting salt. Off to a good start!

I downloaded the LIFE iOS app and started tracking the fast. During the rest of the evening I made sure to take in enough water, and that was it. After a normal night of sleep, waking up at 6:20 AM as per usual, I already had nearly half of the 24 hours done. Easy!

Of course, the hard part was just about to start.

Preparing breakfast and then lunchboxes for the kids was weird. My morning routine is so ingrained in me, there were several occasions where I just automatically grabbed something which is part of the routine and then realized: “No, not today”, and had to put it back. No coffee, no smoothie, just that big glass of water with a pinch of salt and some lemon juice. This is delicious and refreshing. So far, so good.

I got through the extensive list of daily morning tasks involving taking care of the kids rather well, just feeling slightly woozy at times, especially when stopping for a minute or two between tasks. After around 12 hours without food, you’re in the fat burning stage when your body starts to run on the stored fats instead of the usually readily available carbs you normally just ate. That energy source is fine but makes you feel slightly less energetic. I know that feeling quite well from my distance running where it’s a constant race to keep the glycogen levels up.

Since I’m streak running on every single day for over two years now and I’m not planning to stop, the run was on today’s plan as well. Right after doing the family laundry. I took it very slow and did just eight kilometers at low effort.

I’ll be honest, it felt horrible. The run completely sucked. Just like one of those days where there’s just no energy in the body, completely exhausted, no power, no drive, no fun. I stayed at a slow (for me) 5:30 minute/km pace and my heart rate stayed very low, too.

Afterwards, just more water with a little bit of salt. I’m at 1.5 liters for the day right now and it’s just half past ten. I tend to drink a lot more than most people I’m aware of, so that’s very much standard for me. Looking at all the ready to eat food we have lying around in the kitchen made me suddenly aware of how much we’ve actually got.

“This is stupid. Why am I doing this.”

Starting at 11:00 AM, some 16 hours into the fast, it started to really suck. I felt sad, lazy, and was thinking about food all the time. Those poor people who experience this every day!

After my strength training, which I kept very light today, I felt dizzy. When I sat down at the computer to do some emailing and coding work, it was very hard to focus and keep my brain in that space. I tried to get started with some writing instead, but inspiration and concentration weren’t my friends at this stage. I didn’t even feel like watching anything. Just thinking about food.

So after some light work I decided on a half hour power nap around noon which I normally never do. This slightly refreshed me.

Six hours to go. Judging right now, I feel sure that I’m not going to do this again. Two and a half liters of water.

Now follows the strenuous two hour weekly grocery shopping tour for the whole family. On a day of fasting, it’s especially tough to buy all the food for week of eating for our family of six. I bought quite a bit more than was necessary, understandably, and I wanted to eat it all. All of it, right then and there.

But I got through it and carried those 60-70 kilograms worth of food back home, fighting quite the headache by now.

Since I’m a stay-at-home dad at the moment, the kid collecting tour on my bike was due. Shortly before 4:00 PM I had the four of them at home safely, still with a headache, but getting on with it.

I’ve got a dry mouth but my stomach feels full with water and I don’t really want to drink even more. Tried writing some code for another half an hour, which worked surprisingly well this time around. But the dizziness was an obstacle. Preparing dinner for the kids then was the last big challenge, and sitting next to them while they happily ate away, even more so. That peanut butter smelled so delicious! Less than an hour to go.

Thankfully, MrBeast just came out with a new video, so the kids and I watched it and it was calmingly distracting me. Incidentally, the guy had a huge video last year in which he tried water-only fasting for 30 (!) days. He didn’t make it (spoilers), but got very far. It’s an interesting and controversial watch, even featuring star chef Gordon Ramsay, take a look.

After the video I had just ten more minutes to go to the full 24 hours and I literally started counting down while preparing a big dinner feast for myself.

It felt amazing to finally eat! The dizziness didn’t go away right then, that took about half an hour to an hour longer. Probably because I chose healthy foods like a bulgur salad and some hummus to break the fast, which don’t spike the insulin that much.

😴 The Next Day

I felt amazing the next day. So the part that makes many people think fasting is good for you can in fact be experienced. My mood was great, my daily run very fast without much effort, all my daily tasks were easily accomplished with good focus and results. I would say that I felt better than during a standard day.

🧑‍🎓 What I Have Concluded

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  • This was one of the best articles I've read so far in telling about a race. I couldn't put it down. Your details were so awesome. You made New York just come alive.

    Betty J.

  • Great review, enjoyed reading it and recognize lots off related subjects and hurtles. I’m amazed by all your running and races well done.

    Andre S.

  • Great article! I've read so many long blogs only to get bored in the middle as I suffer terribly from ADD and move on to other things. Yours has been one of few that held my attention all the way to the end.

    Chae B.

  • Your good humor and ease in telling stories make this blog a really cool space. Nice review.


  • Amazing effort Tim, well done! Thank you for taking the time to write down your thoughts, feelings and memories from the event. There’s always something to learn from your posts and this one was no exception!! Another cracking read.

    Tom K.

  • What a ride! Surely the race, but also reading about it. Thanks for taking the time to write up such a detailed report, almost feel like I was there.

    Till F.

Is it worth to feel this bad for a day or longer, because the day after will feel better? When I compared my subjective experiences of how bad it felt during the fast to how good it felt after it, I think that in the end it was a clear net negative. The high didn’t offset the low for me.

It helped me to understand how bad hunger can be, even though I’ve only experienced it for that relatively short timespan of 24 hours. But that was enough to leave a big impression on me. It isn’t great and just because our bodies can survive this and use up the stored energy reserves which are our fat, doesn’t mean it’s a wise thing to do.

🧑‍🔬 The Scientific Situation

Which brings me to the scientific backgrounds. I’m not a physician but I am married to one, as stated. Of course, Sophie took an interest in my experiment and gathered and shared some information about the process. There’s a reason that fasting is most often accompanied by a disclaimer saying that you should consider this together with a doctor before trying. Under certain conditions, fasting can present a serious risk to your health.

But what if those conditions aren’t met and you’re a perfectly healthy person, will it then help?

The short answer is, probably not. There is no serious scientific evidence to support that fasting will improve our health. A few studies, like this one, present some findings claiming that there are links to some benefits, but often these studies aren’t very meaningful (e.g. here, we only have 12 volunteers in the tested group and the study doesn’t state any specific proven benefits, just observed “changes” to their bodies’ protein structures).

The situation is unclear at best. But we shouldn’t forget that this doesn’t necessarily mean there is no benefit – science might just have not discovered it yet. 

It’s obvious that we’re burning fat when fasting, so that can be considered a health benefit for many people, because being overweight comes with a lot of inherent health problems like an increased risk of heart disease and several types of cancer. 

But for me, it isn’t necessary to lose weight in order to reduce those risks. I weigh 75 kilograms at a height of 1.90 meters (165 pounds on 6’3”), which puts my BMI at 20.8, nearly at the center of the recommended area of 18.5 to 24.9 for adults. 

An argument often stated is that when the body reaches the “autophagy” (i.e. “eating oneself”) state, it breaks down the weakest and oldest cells of the body first and gets rid of them, replacing them with fresh new cells afterwards, therefore sort of “cleaning house”. But there is no evidence for it actually being the case that the body selects certain weaker cells. To the contrary, the body uses any of the available energy storages to survive, including the “good” cells in our muscles. 

☣️ What About the Detoxing Effect?

There isn’t any “detoxing” happening. The term is a bit of a marketing scam. Of course we consume some amounts of toxins every day, this can’t be avoided. But we have organs whose designated job it is to get rid of those every day of our lives. That’s our liver and our kidneys, mainly. Also, our skin eliminates lots of toxins via sweating. The lungs get rid of carbon dioxide, which is a metabolic waste product for us and a toxin as well. Our whole digestive system is nothing more than designed to select the useful bits we consume in order to use them and get rid of the unhelpful stuff we don’t need. And last not least, there is our lymphatic system, which cleanses the fluid surrounding our cells by removing impurities and waste products, protecting our bodies from infection and disease, too.

Our whole body is a detoxing machine!

The best way to help this most amazing device we’ve all got is not to remove the nutrients needed for everything to work well, but to provide it with them.

There are certain diseases, like Crohn’s Disease, which MrBeast suffers from, where it might make some sense – but even then, you should definitely talk about this with your doctor and they might rightfully advise against it depending on your individual situation.

But one thing remained and occupied my mind for a while:

⛪ Why, Then, Do So Many Religious Rituals Revolve around Fasting?

For hundreds, even thousands of years, people have been doing cultural fasting rituals.

The Christians typically fast during the 40 days leading up to Easter. The Muslims observe Ramadan, a 29-30 day fast. Both don’t completely outlaw food during these long periods, but make a point of limiting (certain) food intake to certain short periods. There are many different Buddhist traditions involving fasting. Judaism and Hinduism both also have different ways of doing it.

The reasons given by the religious leaders is usually something spiritual like getting closer to God or helping strengthen the faith in a related way.

But is there maybe more to it? Have these traditions evolved because it’s also somehow good for the body?

Given the scientific situation, I wasn’t too sure about that. Then I remembered the popular history book I’ve read, “Sapiens” by Yuval Noah Harari. Harari explains why religions most likely evolved. It’s about the evolutionary advantage it presents if a larger group has a stronger inner connection and bond. If people believe in the same framework, they tend to stick together, fight together, defend the tribe together. That definitely aids the survival of the tribe, spreading out the genes and the religious sets of believes with them.

And there’s another thing which helps the tribe stick together, and that’s going through hardship. There aren’t many things which are as beneficial to it as that. A tragedy or a collective trauma brings everyone to the same table and increases the focus on moving forward supporting each other.

Maybe fasting was a device invented by the religious leaders to artificially create this strong connection? Artificial or not, the hardship experienced together would have the same outcome. The euphoria and festivities after breaking the fast will probably have helped convince people that it was worth it in the short term.

👍 Would I Recommend It?

If this hypothesis is correct, it wouldn’t make much sense to do fasting alone. But it could certainly help develop a sense of belonging and comfort in our increasingly fragmented and lonely society, to do fasting as a group, be it for religious or other reasons.

Even apart from that, I’d say everyone should give this a try who hasn’t yet. Obviously considering your personal health situation first with a professional, as stated multiple times. 

Having this experience of hunger and how the mental and physical well-being is affected by it broadens the mind and sharpens our understanding of the situation many people still unfortunately find themselves in all over the world.

This has to change. Let’s start with ourselves and conjure up more empathy.

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