I have to admit, when I first heard about yet another “revolutionary diet claim” called water fasting, I was a little confused.

So does it mean abstaining from water? Or does it mean abstaining from food while only consuming water?

Glynn’s Guide

  • Three days of fasting seems to be the best bang for the buck if you’re looking for extremes.
  • Any more than 3 days and you should add mineral water and 1teaspoon of salt a day to your intake
  • Simply adding a 24 hour fast 1-2 times a month will “reboot” your metabolism.
  • Intermittent fasting is just as effective as a longer-term water fast. You can read more about intermittent fasting here.

Turns out, it’s a fixed period of abstaining from food while only drinking water. But let’s review both concepts.

There’s definitely validity to abstaining from food while drinking only water for a period of time. We’ll call it a reboot of your metabolism. A review of the peer-reviewed research shows:

  • Improved glucose tolerance
  • Improved insulin sensitivity
  • Weight loss
  • Improved blood lipid profile

Does water fasting mean no water?

This is not what this current practice of water fast means. So if you’re thinking about abstaining from water for a period of time, Don’t do it! Period. Your vital organs will not appreciate being dehydrated. It impairs their function.

A water loss of 1-2% of our body weight leads to cardiovascular strain, fatigue, and reduced muscular work capacity. Please don’t get yourself into this situation. On this planet, water is life!

Does water fasting mean a fast with just water?

Yes, this is a more appropriate explanation of this method. The period of time typically varies from a 24-hour fast to 7-day fast. It’s easy to get this mixed up with intermittent fasting. But this is fasting for a fixed period of time randomly.

In a way, it’s like a reboot for a lot of your metabolic functions. And the research backs many of the claimed improvements. Once a quarter seems to have good benefits. But I’m sure many take it to a more extreme and do it once or twice a month.

Is a long fast more effective than intermittent fasting?

Not necessarily.

I’m finding a consistent trend in peer-reviewed literature stating that intermittent fasting is actually more effective than a long fast.

The improvements that are superior include weight loss and insulin sensitivity. These are both significant aspects of health. To go back a few paragraphs, it’s like several little reboots a week that adds up nicely.

Does water fasting cause weight loss?

Water Fasting Weight Loss

Yes, water fasting causes weight loss. We begin by depleting our glycogen stores, followed by fat and lean tissue (predominantly muscle). The amount of lean tissue loss is dependant on the duration of the fast.

I’m personally opposed to a fast more than two days unless deemed medically necessary.

Can water fasting detox your body?

Oy! Every time I hear the phrase “detox” or “cleanse” regarding our health, I want to lash out! Our systems are far more complicated than simply ridding yourself of toxins via elixirs or fasting. Our liver and kidneys do a remarkable job of clearing unwanted chemicals and waste products from our bodies.

I will go this far to say the fat loss may shed stored environmental chemicals. I, of course, speak of the chemicals we’re exposed to from industry. Otherwise, the “reboot” of some of the metabolic systems has a real impact.

Potential Dangers of Water Fasting

Perhaps one of the most prevalent dangers of water fasting involves medications. Many medications require ingestion with food. This can be problematic for those individuals requiring scheduled life sparing medication.

The other aspect that I find more relevant is the loss of lean muscle tissue. Weight loss will occur during a fast. Initially, it’s glycogen stores. Then we’ll begin to utilize lean muscle tissue and fat tissue to sustain life. This results in a significant decrease in force contraction (weakness).

Short term fasts (1-3 days) will have minimal impact on muscle loss, but longer fasts will result in more lost. Although studies have shown a return to normal levels upon refeeding.

What type of water for a water fast?

If you’re fasting for more than two days, you may want to consider adding some electrolytes. I discuss that in the next section.

What about electrolytes for a water fast?

Adding additional electrolytes (minerals) is only relevant if you plan on fasting beyond two days. If you’re concerned, add mineral water and some salt to your intake. Don’t overdo it though. A teaspoon of salt and a few bottles of mineral water a day will do just fine beyond two days.

Can I have tea or coffee during a water fast?

Tea Coffee Water Fasting

I recommend avoiding both tea and coffee during a water fast. Besides, the label “water fast” indicates only drink water.

Is water fasting healthy?

There’s nothing unhealthy about a 24 hour to 3-day water fast. I would only consider fasting longer if you have no health concerns.

In the past, I probably would have suggested avoiding a fast. This is because I was always concerned about muscle loss after 24 hours without food. Besides, I always ate 5-6 meals a day of high protein and moderate carbohydrates and fat. I continued to gain muscle while staying lean (a difficult task).

So, as far as I was concerned, nothing was broken. No need to try alternative methods.

Now, all of that said, years of literature reviews and experiences have opened my eyes to many other successful alternatives. In fact, our ability to gain and keep muscle seems to improve after a fast.

And our cholesterol, insulin sensitivity and body weight all improve.

Someone asked about a 40-day water fast.

I don’t care if it’s a 3-day water fast, a 5-day water fast, a 7-day water fast, a 14-day water fast or a 40-day water fast. They all seem to elicit the same benefits. In other words, I would not jeopardize your health and lean muscle tissue with anything longer than 7 days if you’re an extremist. Seriously, seven days with no food is extreme, but anything longer is overkill.

Three days seems to be the best bang for the buck if you want to push the limits with the best bang for the buck.

Will a 24-hour water fast hurt you?

Not at all. Our metabolisms are well equipped to manage without food for a fixed period of time. Obviously, food was not always in abundance. But depending on one’s geographic location, water has always been in abundance.

As a kid, I always watched the original Star Trek and I’ll never forget about an episode, where aliens described Kirk and his crew as bags of water. What an insightful fictitious alien! We need water long before we need food.

Will a water fast improve my mood?

Initially, I would have said no, but after a review of the psychological literature, I have to say yes. Fond states,

“Many clinical observations relate an early (between day 2 and day 7) effect of fasting on depressive symptoms with an improvement in mood, alertness and a sense of tranquility reported by patients.”

What about bodybuilders preparing for competition?

Bodybuilder Water Fasting

This is an outlying circumstance. It is not relevant to most applications of a water fast. Typically, 24 hours before competition, bodybuilders will cut their water.

This practice combined with diuretic pharmaceuticals (not all of them) will yield very tight skin. This allows the striation of the muscle to be visible on stage. It’s not a safe practice, but it is normal in the world of bodybuilding.

An interesting observation

Over the years, I have had the opportunity to train individuals during the Ramadan fast. For those of you are unsure how Ramadan works, there’s no food or drink permitted during daylight hours. It resembles a variation of intermittent fasting (aside from water) closely.

Energy levels were always lower than normal, but this was to be expected. And they always lost weight. Again, this was to be expected. During the fast, I noted very little muscle gain in my clients.

But here’s an interesting observation. After the completion of Ramadan, it was easy for both male and female individuals to gain muscle mass quickly.

This certainly coincides with some of the intermittent fasting claims.

Conclusion on Water Fasting

So, if you’re still intrigued and you want to partake in a water fast, I suggest no more than 3 days. It seems to be the best bang for the buck. Start with 24 hours if you’ve never fasted before. Nonetheless, it seems to be a great method to reboot your metabolism and help with glucose tolerance, blood lipid profile and blood sugar.

If you’re doing it to improve sleep or mood, there may be some legitimate benefits. You have nothing to lose with at least trying a 24 hour fast. Just drink plenty of water during the fast and avoid very strenuous activities.

Water Fasting FAQs

Is water fasting a detox?

Ugh! No, our bodies are not that simple. Please eliminate the association of detox and human metabolism from your mental associations.

Will water fasting lower blood pressure?

Yes, 1-3 days of fasting from food, only consuming water will lower blood pressure.

How to water fast safely?

I would suggest water fasting for no more than 3 days. If you’re inexperienced, start with fasting (with only water consumption) for 24 hours. And then progress from there.

When water fasting, how much to drink. I will not quantify this, but rather say that you should drink enough to prevent dry mouth.

Can you water fast while pregnant?

Physically, yes, but you will compromise your lean tissue for your baby. So, I would not suggest water fasting while pregnant, period.

What happens during water fast?

First, you deplete your glycogen stores (read blood and liver sugar), then you begin catabolizing stored fat and lean tissue. Yes, you lose weight, but it’s not all fat. Keep that in mind. An intermittent or prolonged water fast should be done for improved glucose tolerance, insulin sensitivity, blood chemistry and overall weight loss.

Can a water fast improve sleep?

I can’t state from experience, but fasting has been shown in peer-reviewed literature to help with sleep disorders.

Will water fasting get rid of stretch marks?


Will water fasting cure cancer?

Seriously???? No…

Who should water fast?

Anyone who wants to improve blood chemistry with a “reboot.” It’s also a great way to start intermittent fasting.

Water fast to kick start keto?

Yes, a 24 hour fast will help with an initial start to a ketogenic diet. It’s not necessary, but it will expedite your goal of achieving ketosis.

Question for You

What have you experienced when fasting for more than 24 hours?

References on Water Fasting

Guillaume Fond, Alexandra Macgregor, Marion Leboyer, Andreas Michalsen, Fasting in mood disorders: neurobiology and effectiveness. A review of the literature, Psychiatry Research Volume 209, Issue 3, 30 October 2013, Pages 253-258.

M N Harvie, M Pegington, M P Mattson, J Frystyk, B Dillon, G Evans, J Cuzick, S A Jebb, B Martin, R G Cutler, T G Son, S Maudsley, O D Carlson, J M Egan, A Flyvbjerg & A Howell, The effects of intermittent or continuous energy restriction on weight loss and metabolic disease risk markers: a randomized trial in young overweight women, International Journal of Obesity volume 35, pages 714–727 (2011).

Aronson HB, Horne T, Blondheim SH, Davidson JT, Blondheim DS, Effect of a 24-hour food-and-water fast on viscosity of whole blood and plasma, Isr. J. Med. Sci. Oct 1979, 15(10):833-835.

Li C., Ostermann T., Hardt M., Lüdtke R., Broecker-Preuss M., Dobos G. & Michalsen A., Metabolic and Psychological Response to 7-Day Fasting in Obese Patients with and without Metabolic Syndrome, Forsch Komplementmed 2013;20:413-420

M. V. Pahl, N. D. Vaziri, F. Akbarpour, A. Afrasiabi, and R. Friis, Effect of Rapid Weight Loss With Supplemented Fasting on Serum Electrolytes, Lipids, and Blood Pressure, J Natl Med Assoc. 1988 Jul; 80(7): 803–809.

D M Russell, L A Leiter, J Whitwell, E B Marliss, K N Jeejeebhoy, Skeletal muscle function during hypocaloric diets and fasting: a comparison with standard nutritional assessment parameters, The American Journal of Clinical Nutrition, Volume 37, Issue 1, January 1983, Pages 133–138

John F Trepanowski and Richard J Bloomer, The impact of religious fasting on human health, Nutrition Journal 2010, 9:57

Krista A Varady, Surabhi Bhutani, Emily C Church, Monica C Klempel, Short-term modified alternate-day fasting: a novel dietary strategy for weight loss and cardioprotection in obese adults, The American Journal of Clinical Nutrition, Volume 90, Issue 5, November 2009, Pages 1138–1143.

Krista A Varady, Marc K Hellerstein, Alternate-day fasting and chronic disease prevention: a review of human and animal trials, The American Journal of Clinical Nutrition, Volume 86, Issue 1, July 2007, Pages 7–13

Water Fasting: Benefits, Dangers, Weight Loss, and How it is Done

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