Water Fasting Benefits, Dangers & My Personal Experience

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Wellness Mama » Blog » Health » Water Fasting Benefits, Dangers & My Personal Experience

Several years ago, I started experimenting with water fasting. Over the years, I’ve found it to be an amazing experience, so much so that I continue to do it every year, several times a year. I’ve seen so many benefits, not just health-wise but also mentally and spiritually. It’s been a fun journey to take as I’ve learned more and grown stronger with each fast I take.

Before I share more about my experience with water fasting, I must emphasize that this is MY experience. While fasting is generally considered safe for short amounts of time, not everyone can or should try it. What works for one of us might not work for everyone. 

This is what worked for me.

What is Water Fasting?

As the name suggests, it’s fasting while only consuming water. Nothing but water. Herbal teas, black coffee, calorie-free drinks, and supplements are not part of water fasting. Just water. You can add in Himalayan salt to your water, which is helpful to maintain electrolytes, especially in the first three days when you lose a lot of water.

This year, I’ll also be experimenting with drinking more salt water and minerals on the water fast and possibly taking enzymes like Masszymes, which I theorize won’t break the fast but might speed up autophagy.

If it sounds tough, I can say from my experience, that water fasting is much easier than other types of fasting (bone broth, juicing, etc.), which are more dietary modifications and not fasting. The results are much more profound with water fasting than other fasts. This type of fasting is also called block fasting or long-term fasting.

How Long Does a Water Fast Last?

Water fasting can vary in duration. Short-term fasts of 24-72 hours are considered safe for most people. Prolonged fasting includes fasts of five, seven, or even forty days. I started with a shorter fast of 24 hours to begin and then worked my way up. Now, I typically do a five-day water fast once a quarter and a longer seven-day water fast to start each year off. The longest I’ve fasted is ten days.

Why I Decided to Fast on Water Only

Throughout history, people have fasted by default when access to food was limited or during travel when food was unavailable. In addition, every major religion recommends (or requires) fasting in some way.

But in modern times, the idea of voluntarily going without eating seems absurd to some. Researchers estimate that Americans don’t even eat just 4-6 times a day like we think we do. The actual number is closer to 17-18 times a day.

Don’t think you eat that many times a day? Consider this — from a biochemical perspective, any time we put something caloric in our mouths, there’s a digestive event. Every hand full of nuts, every sip of smoothie between meals, or even a sip of coffee with cream. The body sees all of those as digestive events.

These days, we eat much more, move much less, get less sunlight, and have much more artificial light exposure. The odds are not in our favor.

I decided to experiment with fasting because of all the health benefits. However, I found that I actually felt more mental and spiritual benefits from it than I was expecting. Now, I learn much more about the mental and sort of emotional side of it.

The Benefits of Water Fasting

Although I’ve researched several types of fasts (intermittent fasting, fasting mimicking diet), I decided to experiment with water fasting because of all the benefits experts have discovered.

Studies show many positive effects of fasting, including:

  • It creates autophagy in the body
  • Lowers age-induced inflammation in the body
  • Reduces oxidative damage
  • Lowers NF-kB activation
  • Boosts the immune system

What is Autophagy?

Autophagy literally means “self-eating”. Essentially, during autophagy, the body recycles old parts to create new parts.

Research shows that autophagy is a key part of the body’s ability to detoxify and regenerate itself. Fasting and high-intensity exercise both stimulate it. Even intermittent fasting can have benefits, though the biggest results seem to come from longer-term fasting.

Studies have found that autophagy can lead to decreases in risk of cancer, heart disease, and Alzheimer’s. Other studies found it can increase longevity and reduce all-cause mortality. Recycling = good for cardboard and good for our cells too!

Lower Inflammation and Oxidative Damage

Increased inflammation and oxidative damage correlate to early death, while reduced levels equate to longer life. People who live to be 100+ years old share the common factor of low levels of inflammation in the body.

Studies show that fasting reduces pro-inflammatory cytokines and inflammation in the body. Specifically, researchers at Yale School of Medicine found that a compound called beta-hydroxybutyrate (BHB) inhibits NLRP3.

NLRP3 is part of a set of proteins called the inflammasome, which drives the inflammatory response in several disorders, including autoimmune diseases. These include Hashimotos, type 2 diabetes, Alzheimer’s disease, heart disease, and other auto-inflammatory disorders.

The researchers found that BHB is produced by:

  • Fasting (most effective)
  • High-intensity exercise
  • Caloric restriction
  • A ketogenic diet

Reduce Cancer & Heart Disease Risk

Emerging research shows a link between fasting and reduced cancer risk. This is likely due to the two factors listed above: increased autophagy and reduced oxidative damage/inflammation.

Research also shows that water fasting may slow or halt tumor growth, as well as improve the chemotherapy effects and reduce the side effects. This makes it potentially beneficial when combined with conventional cancer treatments.

Yet another study found that water fasting can help protect the heart against damage from free radicals.

One doctor I spoke to claimed that 1-2 five-day water fasts a year could reduce cancer risk by more than 90%! Even if the results aren’t that dramatic, I decided it was worth a try.

Boost the Immune System

A 2014 study found that water fasting for just three days could regenerate the immune system. The researchers found that fasting “flips a regenerative switch” and prompts stem cells to regenerate new white blood cells.

“It gives the ‘OK’ for stem cells to go ahead and begin proliferating and rebuild the entire system,” according to Dr. Valter Longo, Professor of Gerontology and the Biological Sciences at the University of California and author of The Longevity Diet.

This research makes fasting promising for those with immune problems, those undergoing chemo, and all of us as we age since immune function declines with age.

Improve Brain Function

When fasting, the body switches from burning glucose to burning fat. Instead of glucose, the brain uses ketones for fuel. Ketones are largely considered a more efficient fuel for the brain. For this reason, fasting is associated with increased mental clarity, focus, and concentration.

My Experience Fasting on Water Only

Before jumping into a water-only fast, I researched the potential benefits and talked to several experts. Like I said, I’m not suggesting this type of fast for anyone else; I’m just sharing my personal experience. Anyone considering it should do their own research and talk to a qualified healthcare professional.

For my first fast, I picked a week free of travel or any major activities. This turned out to be a good thing because, fair warning… the first few days of fasting are not fun. At all. But they also aren’t as bad as you might think.

A few days before I start, I focus on eating a lot more green veggies, drinking water, and taking supplements (they aren’t allowed on a water fast). I also make sure my electrolytes are up with homemade electrolyte drinks and add salt to my food.

Testing on the Water Fast

My experiments with fasting are for research as well as the health benefits. To evaluate the effects on my body, I do several types of testing before, during, and after my first fast, including:

  • Full CBC and Thyroid Blood Panel – I ordered without a doctor through Life Extension (click on “lab testing”). I do this before and after the fast to measure results.
  • Ketone Testing & Blood Glucose Testing – I used a Keto Mojo meter for both of these. You want a 1:1 or greater ratio of ketones: glucose in mmol/L during fasting to show autophagy. If you have a regular glucose meter that measures in mg/dl, divide that number by 18 for mmol/L. For instance, my normal fasting blood glucose of 71 divided by 18 is 3.94 mmol/L.
  • Breath Acetone Testing – This test measures the amount of ketones used and can predict fat burned. The blood ketone measurement above determines ketones in the blood, and this one measures how it’s being used. I used this device. Of all the tests, I consider this one the least important.
  • Gut Testing – I tested my gut using Viome before and after to see if there were any dramatic shifts in gut health.

What Kind of Water on the Fast?

Since water is the only thing consumed during the fast, it’s important to make sure to drink high-quality water. I have a whole house filter and a 14-stage under-the-sink filter, so I drink my tap water. Some people prefer to use distilled water while fasting because it’s free of all minerals.

Electrolyte depletion is one of the bigger risks of fasting, so I added some high-quality Himalayan salt to a couple of glasses of water each day. This is supposed to help with headaches and tiredness.

The amount of water is also important during a fast. Drinking too much water can cause problems, as can not drinking enough. Sources vary on the exact amount but it ranges between 2-4 quarts a day. I just drank when thirsty and added a pinch of salt to a couple of glasses a day.

What Products Should You Avoid on a Water Fast?

Sources disagree on what products, if any, should be used while fasting. Some claim that any lotion, toothpaste, or deodorant will create a metabolic change and break the fast. They recommend brushing with a plain, wet toothbrush and scraping the tongue. They also recommend skipping deodorant. Others say that normal external products are fine.

Since I make many of my beauty and personal care products, I felt ok using them. I used a natural toothpaste and used magnesium oil for deodorant, since Epsom salt baths are considered ok. I also used soap daily and didn’t notice any negative effects from this.

Supplements aren’t allowed on fasts. As I mentioned, you can add high-quality salt to your water or use Epsom salts. This helps you balance electrolytes during the fast.

My Day-by-Day Water Fast Experience

The first time I experimented with a water fast, I didn’t know what to expect. I hoped to experience autophagy and increased stem cell activity. I’ve noticed that my experience in previous fasts has been pretty similar, but now that I know what’s coming, I can plan accordingly.

Here is what I experienced day by day:

Day 1

Since I didn’t know what to expect, I scheduled an easy first day. Things started out normal, but by dinner, my body started to notice it hadn’t eaten all day, and the hunger hit. Then the tiredness.

Overall, it wasn’t a terrible day, and I just took it easy. I went to bed around 9 PM that night and got about 10 hours of sleep.

Day 2-3

These middle days were rough. I was still hungry (obviously) but also had fatigue and slight body aches. I also got cold, likely due to the changes in T3 that naturally happen during fasting. So, I spent a lot of time on the couch with blankets these two days.

I wouldn’t say these days were as bad as the flu (though it’s been a long time since I’ve had it), but they were rough.

Days 4+

I loved days 4-7 of my first fast! Energy came back with a vengeance, and hunger disappeared. I was easily 2-3x more productive than normal. Many sources claim this is because you have more time since you don’t have to cook. For me, this wasn’t true because I still had to cook for my kids.

Since I was measuring blood ketones, I know they were above 4.0 on these days, and my adjusted glucose was below it. This means I was in autophagy. Ketones are considered a cleaner and more effective fuel for the brain by some experts. I’m guessing the mental clarity came from the increased ketones.

The one complaint I had during these days was itchy skin. From my research, this can be a common reaction to fasting and weight loss, but an Epsom salt bath alleviated it.

Breaking a Water Fast Carefully

Surprisingly, if not done correctly, one of the biggest risk factors of fasting can be the return to normal eating. The longer the fast, the more important the post-fast refeeding period is. In extreme cases, after long fasts, the body can encounter something called refeeding syndrome. This is where fluids, insulin, and electrolytes get out of balance. In really extreme cases, it can be fatal, so breaking the fast correctly is VERY important!

Sources recommend starting with broth, soft cooked veggies, some gentle fruits, and fermented vegetables. Meat, fish, dairy, and raw vegetables are all a little harsh for breaking a fast, so it’s better to wait until day three post-fast for these. Additionally, it’s a good idea to wait four to five days before adding in caffeine or alcohol in very small amounts.

My refeed looks a little bit like this:

  • Day 1: Broth, soft cooked veggies in olive oil, avocado, berries, and sauerkraut (It all tasted amazing!). I typically break the fast at night and keep my meal to around 500 calories to let my digestive system start working slowly.
  • Day 2: Add sweet potato and more volume of food.
  • Day 3: Add slow cooked meats and fish. Also add in supplements.

My Water Fasting Results

On my first water fast, I felt really good after the middle of day three. The mental clarity I had was amazing! This has been my experience with each fast since that first one. For each fast, I still monitor my blood glucose and ketones before, during, and after.

I also tested my blood levels before and after fasting to make sure it didn’t negatively affect my thyroid. Not only was it not harmful to my thyroid, but my levels actually improved!

The biggest changes I noticed from my fast were:

  • Weight loss – Although this wasn’t the main reason I experimented with water fasting, it was a great benefit. When I did my first fast, I lost over fifteen pounds during a one-week fast, of which twelve pounds stayed off. The other three pounds were likely from water and food in the digestive system.
  • Fasting blood glucose – Before the first water fast, my fasting blood glucose was always pretty good — in the mid-80s most days. While fasting, it got as low as the 50s but has normalized and is consistently 71-73 every morning, even now that the fast has ended. I use this continuous glucose monitor.
  • Thyroid levels – My thyroid antibodies were already low but got even lower after fasting. All other thyroid hormones stayed the same or improved.
  • Cholesterol – My cholesterol numbers and ratios have always been good but improved post-fasting. For a short time, they were slightly elevated, which is normal after fasting, weight loss, or being in ketosis. Then, they normalized and returned to slightly better levels.
  • Faster Adaptation to Ketosis – At the time, I was experimenting with cycling ketosis and using it sometimes for mental clarity. By day one of the fast, I had achieved ketosis and saw levels get as high as 5.8 during the fast. Since then, I’ve been able to get into ketosis in one day by just restricting carbohydrates.

Who Should Not Water Fast

In short, no one should fast just because I did, and everyone should thoroughly research the risks of water fasting and talk to a medical professional before trying it. Common sense and research agree that fasting is also not a good idea for:

Pregnant and Breastfeeding Moms

The time spent growing and nourishing a baby is a special (and exhausting) time and not a time to add fasting into the mix. Fasting during these times can lead to nutrient deficiencies and harmful substances being released into breast milk.


This goes without saying, but growing children should never do an extended fast. In our house, our kids sometimes choose to “fast” for one meal rather than eat a food they don’t love or if they aren’t hungry. This encourages them to listen to their bodies and only eat when hungry. It is not the same as an extended fast, and children should never restrict calories for extended periods of time.

That said, kids often don’t want to eat much when sick, and as long as they get enough fluids, this is generally considered okay.

Those With Medical Conditions

Anyone with a health condition or chronic disease should talk to a doctor before attempting any major dietary change, such as fasting. Those with gout, kidney disorders, eating disorders, or diabetes should not fast unless under direct medical supervision.

The Bottom Line of Water Fasting

I’ve had a positive experience with water fasting. Although the first few days are a little rough, I really appreciate the benefits it has on my well-being. I’ve continued to complete fasts every few months and complete one longer water fast at the beginning of each year. I’ve enjoyed the mental clarity and the physical benefits each time. 

Have you ever tried a water fast? If so, what was your experience?

Additional Learning:

  1. Alirezaei, M., Kemball, C. C., Flynn, C. T., Wood, M. R., Whitton, J. L., & Kiosses, W. B. (2010). Short-term fasting induces profound neuronal autophagy. Autophagy, 6(6), 702–710.
  2. Castello L, Froio T, Maina M, et al. Alternate-day fasting protects the rat heart against age-induced inflammation and fibrosis by inhibiting oxidative damage and NF-kB activation. Free Radic Biol Med. 2010;48(1):47-54.
  3. Glick, D., et al. (2010). Autophagy: cellular and molecular mechanisms. The Journal of pathology, 221(1), 3–12.
  4. Mah L., Ryan K. Autophagy and Cancer. Cold Spring Harbor Perspectives in Biology. 2012;4(1):a008821.

  5. Zare-Shahabadi, A., et al. (2015). Autophagy in Alzheimer’s disease. Reviews in the neurosciences, 26(4), 385–395.
  6. Shirakabe, A., et al. (2016). Aging and Autophagy in the Heart. Circulation research, 118(10), 1563–1576.
  7. Brandhorst, S., et al. (2015). A Periodic Diet that Mimics Fasting Promotes Multi-System Regeneration, Enhanced Cognitive Performance, and Healthspan. Cell metabolism, 22(1), 86–99.
  8. Levine, B., & Kroemer, G. (2008). Autophagy in the pathogenesis of disease. Cell, 132(1), 27–42.
  9. Lee, C., et al. (2012). Fasting cycles retard growth of tumors and sensitize a range of cancer cell types to chemotherapy. Science translational medicine, 4(124), 124ra27.
Katie Wells Avatar

About Katie Wells

Katie Wells, CTNC, MCHC, Founder of Wellness Mama and Co-founder of Wellnesse, has a background in research, journalism, and nutrition. As a mom of six, she turned to research and took health into her own hands to find answers to her health problems. WellnessMama.com is the culmination of her thousands of hours of research and all posts are medically reviewed and verified by the Wellness Mama research team. Katie is also the author of the bestselling books The Wellness Mama Cookbook and The Wellness Mama 5-Step Lifestyle Detox.


127 responses to “Water Fasting Benefits, Dangers & My Personal Experience”

  1. Talia Gonzalez Avatar
    Talia Gonzalez

    Hi katie,
    Can you discuss exercise during water fasting, is walking ok? Also, did you lose any muscle during the fasting, how were your lifts post fast??

    Thanks 🙂

  2. Mary Uhlir Avatar
    Mary Uhlir

    This comment comes years after you wrote this, so going you might still reply. I just finished a fasting mimicking diet. You said you’ve done this as well over the years. Can you speak to the differences you experienced between the two? I have not done a water only fast.

  3. Val Clark Avatar
    Val Clark

    I had been pregnant or nursing almost non-stop for the last 17 years. I thought I had weaned my last child, so I was eager to start water only fasting again. I did a 7 day fast, then 2 months later I was doing a 10 day fast and discovered I was pregnant! I definitely don’t recommend fasting while pregnant, but if we look at other cultures, people in the poorest countries carry babies and give birth having only a fraction of the nutrition that we have access to. I was really concerned about harm to my baby, but everything turned out fine.

  4. Darla Avatar

    Hi Katie!
    I’m on day 5 of hopefully a 7 day water fast (actually I had aprox 3/4 c of bone broth last night because I was just so tired, hungry etc.) but back to it today because I really want to complete a 7 day fast (I realize that technically I’m not but I’m close). I’ve been reading LOTS of articles, watching Youtube videos, listened to some of your podcasts, etc. Prior to starting this fast I’ve done a series of 48 hour fasts for the past 3 weeks. I’m pretty much at a weight that I’m okay with – at the start of this fast I was 120-124 – I fluctuate alot from morning to night (I’m 5’2″, but in my late 60s). Unfortunately I have not experienced the brain clarity nor surge of energy that a alot of people (including you seem to experience) I’M HUNGRY AND TIRED AND LETHARGIC!!! But I’m determined to carry on. I have a few things in common with you i.e. Hashimotos, and I’m doing this more for the autophagy than anything else, and it would seem I’m acheiving that – my BP is way down!!! Hopefully it will stay down – fingers crossed. I’m wondering if my starting weight might have something to do with why I’m so tired. Also, you stated in your post about your experience that you planned to do more 7 day fasts. Have you? Can you do an update for us? Thanks so much

  5. Demetra Avatar

    You said those who have diabetes should not do the water fast with about prediabetes and anemia.I would like to try doing a water fast.

  6. Joy Avatar

    Hi Katie,
    I have been researching alternative therapies, foods, etc for my fam for years, but never was bold enough to take it to a blog. I was very pleasantly surprised to find your wonderful blog and have tons of respect for it.
    I would like to make a suggestion for the above article. It’s one of those things that should be obvious, but I missed it. (Indeed, it may be there, but I missed it if it is.)
    Please advise that there should be NO exercising during a water fast as it destroys muscle tissue. This is my first water fast, and I learned it the hard way. My fault for not doing more research.
    Also, should the bone broth be salt-free? I have read elsewhere that a very salty dish is a big no when refeeding.

  7. Rosemary Avatar

    Thanks for this great article. I was wondering if you would be willing to expand it to talk about how you managed to feed your kids while fasting. This has been the big thing holding me back–cooking 3 meals a day for my kids while fasting completely? That sounds really challenging. I would love the addition of some tips or your experiences with how this was for you. Thanks!

  8. Tom Winnicki Avatar
    Tom Winnicki

    Just wrapping up my 7+ days water-only fast. Broke my 5+ days record from 2018. Blast!!! I didn’t know you could add some Himalayan salt to the water… next year.

    From what I read on this site and others, I had similar experiences. Days 1 and 2 are the hardest. You have to ‘fight’ with your stomach brain (it has few hundred million neurons), ‘telling’ it that it won’t be getting any food for several days and not to send you any hunger signals or you’ll both suffer. By day 3 you stop feeling hunger. It’s good not to be around tasty food where you can smell it and see people eat. One effect I’ve noticed, and another fellow reported this too after his fast, the pressure behind my eyes lowered. Not yet sure what that means. Will need to do more research. Better not to undertake any strenuous activity as it will tire the body very quick. It takes a lot longer for the body to convert fat reserves into energy. So if one’s job requires a lot of physical activity, it’s better to do the fast while on a holiday.

    Last year (2018) I ended the fast without easing in. If I recall correct, I had 6 soft-boiled eggs, bread with lots of butter and seasoned salt (which tasted better than usual). It was a bit hard on the stomach, had some cramping, but otherwise I was fine. Also, this year (2019) I did not ease into the fast. I stuffed myself pretty full at noon last Saturday. Will start easing in on Sunday morning.

    Plan to do 10 days next year.

  9. Jason Avatar

    would this have any effect on people who take prescription medications?

    Can you add a slice of lemon in the water?

  10. Byran Avatar

    Thank you for the great information! I’ve found water fasts to be extremely beneficial for my health as well, but I have always been curious about the impact on my microbiome. Do you happen to have the results of your viome tests (pre/post)?

    From my understanding, during the process of autophagy the microbiome still receives nutrition through the breakdown of old cells and less resilient microbes (really good!). And there seems to be a lot of evidence that prolonged fasts can reduce immune reactions and food allergies through the same mechanisms.

    But sometimes I’ve found that I have a decreased ability to process fruits/vegetables and I am curious to see if the fiber fermenters (generally firmicutes) goes down, because the lack of fiber during the period. Did you notice a change in your microbiome function or ability to process foods?

    Thanks again for sharing and documenting such great information!

  11. Emily Avatar

    Hi Katie, in your opinion, would it be ok to add in an electrolyte packet (like Elemental Labs) each day of the water fast, rather than sea salt, or would you just stick to the sea salt?

  12. K.B Avatar

    I have Hashimito’s as well. Did you continue to take your meds for the duration of your fast? I’m starting my water fast today, but I don’t feel like I should stop. Just curious what you chose to do. Thank you

  13. Nikki Avatar

    Hey! Loved the pst. Quick question, if I decide to use distilled water for the fast, should I still add the Himalayan salt to it? What other type of water would you recommend instead of distilled? Spring?
    Thanks xo

  14. Kelly Avatar

    Hello and thank you for all of your work. I appreciate your gift for breaking down complex topics into actionable steps. I was on board with fasting (especially intermittent) until Christa Orecchio talked about not fasting if in a state of stress or adrenal problems and Dr. Longo talked about not fasting longer than 12-13 hours. Do you have thoughts on those opinions and how you reconcile that with the information you provided in this article? Thank you.

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