How to Do a One-Day Water Fast

Monday Jan 16 | BY |
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Yesterday I fasted for 36 hours on water. It had been a little while since my last one-day fast and I felt like starting the practice again.

When I fast, I don’t drink any juice. I find fasting easier that way, and I believe that juice fasting maintains hunger without leading to as many benefits.

I also never fast on a “schedule.” Even though last year I fasted every week for 36 hours for several months in a row, I stopped after doing enough of it. Always listen to your body when fasting. (But the trick is knowing how to listen!)

I also don’t practice such as eating only 500 calories for one day, such as in the 5:2 Diet. It’s easier to fast drinking only water. That way there is nothing to organize, nothing to think about, and you stop the fast whenever you are ready.

The Benefits of a 24 to 36 Hour Fast

A short fast is not true fasting because the body never fully enters into ketone metabolism, where it burns body fat exclusively for energy. So it’s more a “digestive rest.” But it offers quite a few benefits:

  • Reduced blood lipids (decreased triglycerides and LDL cholesterol)
  • Lower body fat
  • Reduced blood pressure
  • Reduced chronic inflammation (CRP, IL-6, TNF, BDNF, and more)
  • Reduced oxidative stress
  • Reduced cancer risk
  • Increased fat burning
  • Improved appetite control
  • Increased insulin sensitivity and decreased insulin levels
  • Improved cardiovascular function
  • Improved memory and cognitive function

My main reason for fasting fast is because it makes me feel good.

It’s the best way I found to reset real hunger and appetite, uplift mood and get some rest.

And even though fasting is never without some efforts, I have enough experience with it to slip into a 36 hour fast comfortably. Let me give you some tips.

The Easiest Way to Approach a Fast

First, you have to understand that you’ve conditioned your body to eat at certain times. If you feel hungry in the morning, that is not real hunger but rather conditioning. Your body is used to request food whether it’s truly hungry or not.

When you fast for 24 to 26 hours, your body uses its immediate reserves: food still being digested, glycogen in the muscles and liver. It might partly shift to ketone bodies as an energy source but not 100%.

So the first approach to fasting for a day is understanding that you’re not fasting. You’re only delaying your first meal of the day!

How Are You Feeling Now?

The most important piece of advice I can give you about fasting is that you should mentally “chunk it” into blocks of time of one or a few hours.

When you start your fast, you might be thinking to yourself, “Wow, this is difficult. I don’t think I’ll be able to make it.”

What you have to realize, and this comes with practice, is that whatever you’re feeling right now is temporary. The feelings will pass.

My goal when I fast for 24 to 36 hours is to reach the “euphoria” part of the fast when fasting becomes easy. This feeling usually occurs after 4 p.m. After that, fasting is a breeze. In fact, fasting is easy for MOST of the time when doing such a long fast. But it can be difficult some of the time. Here’s how to go about it.

Going to Bed

You can choose to eat a very light dinner or not, eat it early or eat it late. I say do whatever you normally do. Going to bed is the first part of the fast. It’s easy because we fast every night when we sleep!

Fasting Until Noon

The next chunk of the fast is fasting until noon — thereby skipping breakfast. Many people do this all the time, so it’s not that hard. If you regularly drink coffee, I say drink some then or drink some green tea. It’s not worth it going through a fast AND have to detox caffeine at the same time. But switching to green tea is a good idea.

Getting Over the Afternoon Crash

The most difficult part of a 1-day fast is the afternoon. You’ll feel good until right around 1 p.m. or when you start to feel genuine hunger. That’s when you’re starting to think that you won’t last until the end of the day.

If you continue, you might start to feel tired in the afternoon, which coincides with circadian rhythms.

I like to consider this fatigue as “rest.” That’s why I prefer to fast on a Sunday. I will nap at that time.

Whenever I feel like breaking the fast during that period, I tell myself, “Try another hour and decide then.” I know that whatever I’m feeling at the moment will pass.

The Evening High

This is when the fast becomes fun and exciting. The endorphins kick in, and you feel great. Your mood is positive, and it’s then no problem to continue the fast or break it.

You can decide to break the fast for a 24 hour fast.

Or you can choose to go to bed “hungry.” Listen to your body. I usually find that I feel good enough to go to sleep on an empty stomach and fast until the next day. But sometimes I want to eat and break the fast, so I do it.

Sleeping On An Empty Stomach

It’s not that difficult to fast through the night if you put your mind to it. For many people sleep is a bit lighter and for some deeper. I experience deeper sleep on the first days of the fast, so I do enjoy this night! Your energy should be good the next day because fasters don’t require as much sleep.

People who sleep well tend to sleep less during a fast and those who have sleep problems tend to sleep better.

If you wake up in the middle of the night and are genuinely hungry, then break the fast then with some fruit and go back to bed. Otherwise, you can fast until the morning.

The Morning

It’s surprising that most mornings, after fasting for over 32-36 hours, I am rarely hungry. I often have to decide to break the fast because I often feel like I could go on. Sometimes I do go on and wait for hunger to come back, which can take many hours and take me to a 40 or even 48 hour fast.

But if you have important work to do that day, break the fast no matter how hungry you are.

Breaking the Fast

Breaking a short fast is not something that requires a lot of planning. A longer fast weakens your digestion, so re-feeding becomes the most critical aspect of the fast.

I suggest that you eat whole fruit. It will taste amazing! And your energy will quickly come back.

Then act as if the fast never happened. Continue with your day but listen to your body. You may be hungrier than usual or not. Just follow your hunger and don’t question it. Try to eat as healthy as you can, and hopefully healthier than you did before the fast.

After a fast, you might recalibrate your taste buds enough to make a few changes, such as drinking less caffeine, switching to tea, quitting tea, eating more raw food, eating less salt, going vegan, going raw, etc. You’ll be more in tune with what your body needs!

A few people cannot fast for even just 24 hours. People with diabetes fall into that category. Your doctor can advise you.

For more information on fasting, checking The Greatest Cure on Earth

Frederic Patenaude

Frederic Patenaude has been an important influence in the raw food and natural health movement since he started writing and publishing in 1998, first by being the editor of Just Eat an Apple magazine. He is the author of over 20 books, including The Raw Secrets, the Sunfood Cuisine and Raw Food Controversies. Since 2013 he’s been the Editor-in-Chief of Renegade Health.

Frederic loves to relentlessly debunk nutritional myths. He advocates a low-fat, plant-based diet and has had over 10 years of experience with raw vegan diets. He lives in Montreal, Canada.


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  1. Michele Kaye says:

    Great article, and empowering. I will give this a go very soon, maybe next Sunday. Usually do juice fasting although have water fasted before. Like you way of taking it in stages. Thank you Frederic

  2. Kay says:

    Aloha from Maui, Frederic! Your fasting articles had finally inspired me to fast, and I was able to complete 36-, 40- and 34-hour water-only fasts last summer. I actually enjoyed the experiences, treating myself to reading, watching videos, and other purely fun things–no chores!–my own personal “spa” 🙂 My only concern, though, was whether those long periods without food would kick my body into “famine” mode, where it would store more fat for survival. I would greatly appreciate your expertise and thoughts on this. Mahalo nui!

    • Aloha Kay! Glad to hear you’ve been enjoying the spa/fasting days! I also think it’s a way to truly relax. Some research shows that intermittent fasting lead to fat loss overall — not weight gain. The body is programmed to go easily without food for a day. I don’t think it’s the same as people going on starvation diets and lowering their metabolism that way. There isn’t a huge amount of data to back this up but from my experience and that of many others it seems very positive and not leading to fat gain.

      • Kay says:

        Mahalo, mahalo, Frederic! Okee dokee!–now it’s all systems go (literally!) for me to do a 30+-hr fast this week, and listen to when my body wants to do some more. I’m fortunate in not needing to lose weight, yet it’s good clean and clear out. Stay warm up there, and have a truly awesome year. Aloha pumehana

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  4. Karen says:

    It’s time for me to fast again. Thanks for the inspiration Frederic!! I do it on Wednesdays for about a month. It’s never hard for me. Blessings!

  5. Linda Thayer says:

    This is a very nice play-by-play coaching session for getting started in the practice of fasting.
    Years ago, in my 20’s, I discovered Dr. Herbert Sheldon and Natural Hygiene, so I am no stranger to fasting. I’ve read your major books and am aware that Dr. Shelton was one of the formative figures in your health ventures.
    Fasting is so unknown in our society, so you are performing a valuable service for those wanting to reap its benefits but can be side-tracked by doubts when the first headache or stomach-ache sets off alarm bells and family/friends insist that you are harming your health simply by giving your body a break.
    The body knows how to heal itself and will run in the most efficient way when (1) given the raw materials designed for human beings and (2) given the ‘breathing space’ to close down for ‘maintenance’ from time to time.
    Blessings on you as teacher and inspirational guide and on those who learn the benefits of fasting through you!

    • Thanks Linda! I completely agree with you. Fasting is basically a lost or forgotten ability and health practice, and one that is very little understood by most. I forgot to mention that when I fast I don’t tell anybody about my fast, except a few friends who understand this.I like your summary of how the body heals itself.

  6. Edd says:

    The 24 hour fast once a week is an excellent idea. You did not comment on the type or quality of water a faster should be drinking. I usually add a twist of lemon to my water on a fast. What do you think? I used to do the one day fast regularly, but I haven’t done it for a few years. You are inspiring me to start it again.

  7. Debra says:

    HI Fred

    Thanks, great articles, nice and clearly explained. Love the chunking time idea. For me it would be just a another 5 mins, see how I feel then, just another 5 mins! Fasting/resting digestion is so difficult but then rewarding when I can do it. Thanks for the inspiration.

  8. Leo Tat says:

    Hi Frederic

    I don’t believe in using the 500 calories for one day fasts.

    The whole point of fasting is about reducing insulin as much as possible via dietary means.

    So 500 calories that raises insulin breaks the fast.

    I intermittently fast every day by missing breakfast. I then miss lunch 2-4 times a week for longer fasts. I miss lunch mainly for convenience reasons though.

  9. lizzie says:

    Hello Frederic-thank you for breaking it all down so it actually feels doable to me! My question is how much water should we be drinking during a 36-40 hr. fast? Would a certain amount /hr. be suggested? I know generally it’s suggested that a person drink 1/2 their body weight in oz. each day so would that be increased for fasting?

    Thank you!

    • You shouldn’t worry too much about how much water to drink on a one-day fast. This becomes more important on longer fasts. But for one day, just follow your thirst. If your urine becomes too yellow, then drink more. No need to measure anything.

  10. Monica says:

    I’ve heard many things about fasting and I am really excited to try it. My doctor advised me take it slow and start with water fasting. This article really made it more clear for me about what I need to do. Thank you for the useful details!

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