Water Fasting And Exercise: Weight Lifting During A 1-Day Fast

water fasting and exercise-welcome mat

The idea of doing water fasting sparked after reading Nassim Taleb’s Antifragile:

Irregularity has its benefits in some areas; regularity has its determinants. Where Jensen’s inequality applies, irregularity might be medicine.

Perhaps what we mostly need to remove is a few meals at random, or at least avoid steadiness in food consumption. The error of missing nonlinearities is found in two places, in the mixture and in the frequency of food intake.

A few weeks ago, I was at a relevantly down and chaotic phase — I hit the plateaus of self-educating digital marketing, the new semester messed up my regular schedule, and etc. Basically, I felt my life was out of control at the time.

To prove to myself that I could still control most parts of my life with determination (I know it sounds a bit stupid…), I decided to do a “1-day water fasting challenge”.

I did achieve it in the end. I want to share my feelings during the day in case you want to try it yourself.

My Ways Of Doing Water fasting

Attention! I’m not a doctor nor do I have a medical background or anything that qualifies me to give out suggestions on your health. Everything in this post is solely my experience. If you decide to try water fasting, don’t blame me when bad things happen 🙁

Here are my ways of doing it, but since I only did it for a day as a test run, there wasn’t that much to be aware of comparing to a 5- or 7-day one.

  • No food at all. I guess you could tell from the name that the main point of water fasting is — only drink water during the day without consuming food.
  • Drink as much water as I want. Some online articles would suggest you not drink over a gallon of water (~3,785 mL), but I drank as much as I want whenever I was thirsty. One thing to point out is that I didn’t drink an excessive amount all at once. I drank multiple times that day to avoid electrolyte imbalance, leading to water intoxication.
  • Regular activity level. I have heard a few people saying that during water fasting, they would decrease the amount of exercise as much as possible to save energy. Bust during mine, I still have my usual life routines, such as going to classes and even working out.

My Regular Routines

Everyone’s experience of water fasting varies and I think the reasons not only result from our physical differences but also our dietary habits. In my case, I would say my regular diet helps a lot, so I want to list them out as references.

1. I don’t (usually) eat breakfast

I have adopted a “non-brekkie” lifestyle for a few months. Only when I feel a lack of energy and still need to go to the office, would I have a cup of iced latte or a piece of bread in the morning. But mostly, I delay my first meal to 12 pm.

2. I work out with an empty stomach

I used to be those people saying “I need to eat something first, so I could have enough energy to workout!” Now, if I eat anything before a workout, I feel bloated and uncomfortable.

My morning routines would be waking up, drinking some water, and heading to the gym with only water in my stomach.

3. I drink A LOT OF water

If you are my friends in real life, you would know how big my water bottle is. (You will see the picture later.) I can literally use it as a defensive weapon. I drink nearly 2900 mL of water a day, which equals to 4 regular bottles of water you can get from a supermarket.

With these habits, water fasting for me is, more or less, an extreme version of my daily life — delay my first meal even later, drink even more water, and work out with no food afterward.

1-Day Fasting And Exercising

Research about whether working out during fasting (or you can call it fasted training) is a good idea has been conflicting, but it’s possible.

Your workout is fueled by the glycogen stored in your muscle tissue, so even if you don’t consume any food in a day, your muscles will have enough stored glycogen to get you through a workout session.

Will It Affect My Workout Performance?

I would say that whether you think working out while fasting will affect your performance or not — it’s only a feeling

I have experienced both scenarios — working out with and without food consumption prior — before, and the average performance is the same for me. From my experience, I can still keep up with the usual weight I lift even if I don’t eat anything in advance.

There is an interesting research studying the effect of fasted and fed training during Ramadan fasting (no food from dawn to sunset). At the end of the study period, the performance of the fasted training group didn’t get affected, nor the bodybuilders’ body mass or composition.

Don’t Do Fasted Training For Losing Weight

I would not suggest you work out while doing water fasting if your intent is to lose weight, although it’s true that your body will burn more fat if you exercise in a fasted state.

Lots of people would use this trick to lose fat faster, but the overall weight loss depends on long-term caloric deficits rather than increased fat oxidation in the short-term.

If you eat a greasy hamburger and crispy fries after doing fasted training, your calorie intake might still outweigh your calorie consumption. The efforts you make will be in vain.

The Day Before Fasting (Tuesday)

As when people will fill up the oil tank in advance to save money when expecting the gas price to rise, lots of people will devour big meals a day before fasting to store calories.

I did not do that. Water fasting was an instant decision I had after finishing my dinner on Sep 3rd (Tuesday). I knew my next day will be busy with errands, so cutting down the time to eat didn’t seem like a bad idea.

The Water Fasting Day (Wednesday)

During the day, I still did all the tasks I needed to: waking up early, reading, going to classes, working out for an hour, and etc.

In terms of water consumption, I used my 32-oz (~946 mL) Hydro Flask as the measuring unit. After the whole day, I drank nearly 4.6 bottles of water, which equals nearly 147.2 oz (~4352 mL).

water fasting and exercise-hydro flask bottle

Here is my rundown of the day:

6:00 am: Woke up and drank half a bottle of water, then read. 

8:30 am: Went to a governmental office to pick up documents. Everything was fine at this point, since I was used to not eating breakfast.

12:00 pm: Went to class and felt a little bit hungry (especially when walking passed by the canteen) and had a headache. I assumed that the headache was caused by the class rather than fasting.

2:00 pm: Finished a bottle of water.

2:30 pm: Worked out for an hour (Oh man! It was my leg day…). My headache went away once I started working out.

3:00 pm: Finished ⅔ of a bottle of water. As usual, working out made me drink more water. 

4:00 pm: Finished another bottle of water. I wanted to buy a cup of Americano but then realized that I couldn’t drink it.

7:00 pm: Finished a bottle of water. I didn’t feel hungry at all, so I guessed my body was already expected that. Around the same time, I got a phone call from another agency, trying to recruit me. My mind basically couldn’t function at all. I wasn’t sure if it was because of the fasting or it was a big decision for me in general.

10:00 pm: Drank half a bottle of water, did some reading and went to bed.

The Day After Fasting (Thursday)

Here came the time when I could eat again! My brain was so excited that it even broke the rule of not eating breakfast. (My brain: I WANT FOOD!)

Here is the rundown:

6:00 am: Woke up and drank half a bottle of water. I didn’t have any energy and felt quite terrible, to be honest.

7:00 am: Had some Greek yogurt with fruits.

10:00 am: Drank a cup of latte and ate a piece of Italian sandwich. This was when I got my energy back!

2:00 pm: Finished a bottle of water

3:00 pm: Had another cup of latte and a piece of cookie.

8:00 pm: Ate Thai food for dinner and it exceeded the usual amount of food I consume for dinner.

9:00 pm: Finished another bottle of water

11:00 pm: Had half a bottle of water, read a bit, and then hit my bed!

Overall, I ate more than my regular days. My brain and my appetite didn’t care that much after a day without food. The excuse of “I didn’t eat anything yesterday, so I could eat whatever I want” always kicked in.


My experience of doing water fasting for the first time wasn’t as terrible as I thought it would be. At some level, I think it was because I don’t usually eat breakfast and I’m used to drinking a lot of water.

1. Overall hours: The waster fasting challenge was actually more than 24 hours. I stopped eating at 9 pm the day before and started consuming food until 7 am the next day. So I did it for 34 hours in total.

2. Drinking: Based on my regular water-drinking habit, I would drink 3 bottles of water a day as a minimum (96 oz = ~2838 mL). While during the water fasting challenge, I drank 1.5 times more than my regular amount.

3. Energy: Before doing the challenge, I thought water fasting would make me really sleepy and low-energetic during the day. But it turned out that I was more energetic than those usual days when I had regular lunch and dinner. Even when I was working out, surprisingly, I didn’t feel weak.

Since I only did it for a day, my sleeping hours stayed the same. I didn’t sleep more or had any naps.

I would say my mind was clearer during the day, but when I needed to do a hugely important decision, my brain couldn’t function as well as I expected. I would not trust myself to do decisions under that circumstance either.

4. Mood: Lots of people will get “hangry” when their bodies expect to have food. I was surprised that it didn’t happen to me this time. The only negative feeling I got was from the headache, which I wouldn’t assume it resulted from a lack of food. It went away once I started working out.

However, I felt terrible the next morning. That feeling was worse than sleep deprivation. I could imagine that if I want to do a 5-day water fasting, the second and third day would be the hardest time to endure.

Final Thoughts

Doing it for a day was quite great, especially it gave me a sense of control over my life again. One of the benefits I found after the challenge is that, even if I miss a meal, or eat it a bit later, I wouldn’t feel anxious. Because I had this reference, knowing that I would be fine if I skip dinner for a day.

If you want to try this 1-day water fasting challenge as well, my suggestion would be picking a day that you need to do lots of trivial things that are no-brainers, instead of that with important meetings to attend and decisions to make.

There are possible dangers to water fasting. Remember to evaluate your own situation first before doing it. You would probably need to do more research with your own dietary habits.