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What Is Water Fasting and How Safe Is It

Water fasting has been gaining popularity in recent years as an effective weight loss method with many potential health benefits, including reducing blood pressure and protecting against heart disease.

While this eating pattern can help you lose weight quickly, water fasting can be challenging due to its restrictive nature. Is the effort worth it? Or could the risks of this habit outweigh the potential benefits in some instances? And how can one maximize its benefits?

This article will cover all you need to know to understand if water fasting is for you: its benefits, recommendations on how to start your fasting adventure, and tips to stick to it for optimal, long-lasting results.

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What Is Water Fasting?

Water fasting is an intermittent fasting type in which you abstain from food and beverages other than water for a prolonged period. Water fasts usually last between 24 to 72 hours, making them an advanced form of fasting not suitable for beginners.

Traditionally, water fasting was done for religious reasons, but nowadays, this eating pattern is a popular way to improve health.

People usually try water fasting to lose body weight or “detoxify” their bodies quickly. However, the benefits of this habit could be even greater than that: numerous studies have shown that water fasting can reduce the risk of heart disease and certain cancers.

Despite its potential benefits, water fasting can be dangerous if done incorrectly. Before introducing a major change in your lifestyle like this one, make sure that fasting is safe for your current health state (we’ll review some risk groups below), and consult a doctor if you have any concerns.

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How to Start Water Fasting

Water fasting is all about preparation and planning. Here are three steps to help you get off on the right foot.

1. Before: Transition Into Your Fast

As mentioned above, water fasting is an advanced fasting method requiring a certain preparation level.

Before jumping head-first into water fasting (especially if you’re not used to skipping meals), it’s crucial to ease your body into the fasting state to avoid hunger pangs and other side effects of fasting.

One way to do this is by reducing your caloric intake during the days running up to water fast—cutting out snacks, making smaller portions, or skipping your breakfast. Anything goes as long as it helps you eat fewer calories every day.

If you feel like cutting down calories won’t be enough for you, you can practice intermittent fasting for a few weeks before your water fast. This way, you’ll prepare your body for prolonged fasting periods, and you’ll learn how to manage your hunger during your fasting windows.

Changing your eating habits and reducing your caloric intake in the days preceding a fast may also help to minimize any adverse side effects caused by fasting, like food cravings or low energy levels.

2. During: Consume more water than you normally would

Our bodies lose more water than usual during any kind of fast. This is partly because around 20% of your overall fluid intake comes from food—the one thing you’ll abstain from. And losing a significant amount of fluids often translates into electrolyte imbalance.

Electrolytes such as sodium, potassium, and magnesium maintain normal nerve and muscle function. When you don’t drink enough water, your body doesn’t get the chance to replenish lost electrolytes, leading to dehydration and making water fasts much more difficult.

Maintaining your fluid and electrolyte levels is essential to feel good during a prolonged fasting period. Make sure you drink at least 8 glasses of water per day and try electrolyte-infused water if you feel low on energy. Just check the ingredient list before you buy any electrolyte drink, as some brands may contain added sugars that would break your fast.

3. After: Break your fast with a small meal

Once you have completed your fast, you must ensure you break it with a proper meal. Planning this in advance can help you avoid overeating or choosing foods that’ll do you more harm than good.

Even though you will likely want to eat a large meal after prolonged fasting, it’s essential to ease your body back into digesting food by eating small and easily digestible meals.

Examples of foods you can break your fast with include:

  • Fruits and vegetables
  • Smoothies
  • Soups
  • Eggs
  • Dairy products such as milk and yogurt
  • Oatmeal

It’s also a good idea to reintroduce calories in a liquid form first, like with a glass of orange juice or a delicious fruit smoothie, before transitioning into solid foods. If you feel well after this lighter breakfast, you can return to eating normally by the next meal.

What Are the Benefits of Water Fasting?

There are several reasons why water fasting has become so popular, mainly associated with the health benefits that it brings. Let’s dive deeper into 4 of them.

May promote autophagy

Autophagy is a natural process in our bodies in which cells (and parts of the cells) are destroyed and recycled to make way for newer and healthier cells. Studies show that autophagy plays a vital role in longevity and disease prevention, even suggesting that it has some anti-aging properties. It’s worth noting that these studies are still in their early stages, and more research is needed to understand the impact of autophagy in humans.

Autophagy is triggered when your cells are under stress, which can be induced by calorie restriction, exercise, or prolonged periods of fasting. Hence, water fasting can help your body start this self-cleaning process and keep you healthy in the long term.

May reduce inflammation

Inflammation is your body’s natural response to infection and injury. When it goes away after your body heals, it’s called acute inflammation. But if you feel you live in a state of permanent inflammation, you may be suffering from chronic inflammation—a long-lasting inflammatory response triggered by autoimmune disorders, exposure to toxins, or untreated conditions.

This type of uncontrolled inflammation may damage your body and has been linked to many chronic diseases, including type 2 diabetes, heart disease, and even cancer.

While it won’t put an end to inflammation on its own, fasting can help you fight it—both its acute and chronic variants. Time-restricted eating patterns have been shown to decrease inflammation levels by reducing the number of pro-inflammatory cells released into the bloodstream, reducing their inflammatory activity.

May promote weight loss

As mentioned, fasting gained popularity for promoting weight loss without affecting your muscle mass. But how does it contribute to this cause, specifically?

First, abstaining from food for long periods significantly reduces your overall calorie intake, putting you in a caloric deficit where your body burns more calories than it takes in. In this state, your body can start losing weight.

Another way fasting can help you lose weight is by enabling ketosis—an internal process in which your body starts burning stored fat for energy instead of sugar. Ketosis can be reached by fasting for just 12 hours. However, a prolonged fasting period, such as the one you get with water fasting, keeps you in the state of ketosis for a more extended period, enabling your body to burn even more body fat.

May lower blood pressure

High blood pressure is commonly linked to poor heart health and is a crucial cardiovascular risk factor. Taking action to control your blood pressure can help you prevent significant health issues like heart attacks or strokes.

Some studies suggest that water fasting can also reduce blood pressure and other markers for cardiovascular disease, like “bad” cholesterol and high blood triglycerides.

3 Simple Tips on How to Successfully Do Water Fasting

Just like any other advanced type of fasting, water fasting can be quite challenging to follow. Here are 3 tips to help you stick with this new habit in the long run.

Develop a tracking system

Drinking water is integral to water fasting, so you must ensure you’re drinking enough by tracking your water intake. This can easily be done with the help of a mobile app like DoFasting, which includes a handy water log—just set up a water drinking goal (8 glasses of water per day, for example) and record every glass of water you drink.

DoFasting also goes beyond water tracking—it can also assist you in finding any fasting style suitable to your lifestyle and needs, keep track of your fasting history, and provide you with tasty recipes and fast-safe exercises. Select your fasting type and start your journey, while DoFasting keeps you aware of your progress and helps you push through.

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Get comfortable with intermittent fasting

Getting your body used to shorter fasting periods is crucial before trying to go 24 hours on just water: it’ll make the whole experience more manageable and safer for you.

There are multiple less challenging intermittent fasting types that can help you familiarize yourself with time-restricted eating. Studies suggest that it can take up to 4 weeks for your body to get used to fasting, so don’t rush your way into a plan designed for experienced fasters—allow yourself time to prepare for a prolonged period of water fasting.

Pay attention to how you feel

Fasting is not supposed to be a painful or uncomfortable experience. If you start feeling unwell (dizzy, nauseous, or faint) at any point of your fast, stop fasting immediately and get something to eat. 

Feelings like these are your body’s way of telling you something is wrong. Low blood sugar, electrolyte fluctuation, and changes in blood pressure are all health risks of water fasting, which can make you feel weak and unwell. Ideally, if this happens, you should consult with a healthcare professional before trying water fasting again.

Drawbacks of Water Fasting

While water fasting can bring you many benefits, there are several drawbacks you should be aware of before starting. It’s worth noting that these are usually the result of improper fasting and can be prevented with some preparation and caution.

Binge eating

It’s normal to feel hungry, maybe even ravenous, after a prolonged fasting period. However, binge eating right after a prolonged fasting period will undo all the work your body has done while fasting. Even if you feel like you could eat a horse, it’s essential that you break your fast slowly to prevent overeating.

Reintroducing food too quickly after a long period of not eating may even lead to the development of the refeeding syndrome—a shift in your body’s electrolytes that can prove to be fatal.

Though it is essential to eat after fasting, your food intake should increase slowly over a few days to avoid shocking your digestive system and encouraging patterns of disordered eating.

And remember that, to get optimal results, it’s always better to stick to a healthy diet during your eating windows.


As previously discussed, you’re at a higher risk for dehydration when fasting, as you don’t get any water from food.

Dehydration can lead to uncomfortable side effects when fasting, such as a dry mouth, dizziness, or headaches.

Make sure you’re adequately hydrated by drinking at least 8 glasses of water per day. If this sounds like a challenge to you, fill up a water bottle and take it everywhere you go. This will serve as a reminder to drink more water.

Nutrient deficiencies

When done incorrectly, fasting can lead to nutrient deficiencies, which usually develop when a person doesn’t eat enough nutrient-dense foods during their eating hours.

You can easily prevent nutrient deficiencies by eating a well-balanced diet—this means eating plenty of fruits and vegetables, getting enough protein (such as lean meat, fish, eggs, legumes, and dairy products), and prioritizing healthy fats. It’s important to avoid highly processed foods, as they’re mostly empty calories with no nutritional value.

You can also take dietary supplements to combat some of your existing deficiencies and prevent new ones. Not all supplements are fasting-friendly, however, and it’s essential to know which nutritional supplements you can have while fasting.

Who Should Not Fast?

Even though water fasting positively affects health, some people should refrain from trying this habit (or any type of time-restricted eating), as it could put them at risk of worsening their existing conditions or lead to developmental issues. These people include:

  • Children under 18 years old
  • Pregnant women (also those who are breastfeeding)
  • Underweight people or those with a history of eating disorders
  • Those who are taking any type of medications
  • Those with medical conditions that will be exacerbated by water fasting, like diabetes and gout

Even if you don’t fall within the groups mentioned above, it’s always recommended to consult with a healthcare professional before starting any fasting regime. They can help you determine whether fasting is viable for you and may offer their medical supervision to make sure you stay healthy during this new adventure.

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Water fasting has gained popularity as a way to lose weight and improve overall health.

Aside from weight loss, water fasting may reduce inflammation, lower blood pressure, promote longevity, and prevent the development of age-related diseases.

However, this eating pattern is not a one-size-fits-all approach to health. Water fasting is challenging, as it requires abstinence from food for 2 to 3 days straight, can also lead to nutrient deficiencies or dehydration, and may encourage disordered eating when finished.

Before trying out water fasting, familiarize yourself with more manageable intermittent fasting plans, as these may bring many of the same health benefits as water fasting with fewer risks.


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This is an evidence-based article that includes scientific citations. DoFasting’s professional writers and editors prepared the content, which a team of medical experts verified to be accurate.

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