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Is Water Fasting Any Good for You?

8 min read
a woman is holding a glass full of water, smiling, holding thumbs up, junk food like burgers and coke is crossed in the background, water fasting
Melissa Mitri post Reviewer Melissa Mitri post Reviewer
Verified by Melissa Mitri
MS, Registered Dietitian, Former President of CT Academy of Nutrition & Dietetics

Table of Contents

In a broader sense, fasting involves restricting food consumption for a certain period. Among its many forms, intermittent fasting is one of the most studied and proven methods for losing weight. 

Traditional intermittent fasting protocols confine eating to a fixed window but permit drinking non-caloric beverages during fasting.

Water fasting, on the other hand, is a more extreme type of fasting that restricts food and beverage intake while only allowing water during the fast. 

While water fasting is claimed to have various health benefits, it can also pose several risks as it relies solely on water and restricts any sources of nutrients.

So, is water fasting safe? 

In today’s post, we aim to find the answer by weighing the possible health risks and potential benefits of water fasting. 

What Is Water Fasting?

Water fasting is a specific type of fasting where you avoid food or any beverage other than water for a specific period.

Unlike intermittent fasting, which allows tea, coffee, and other calorie-free beverages during the fast, a water-only fast—the name itself implies— only permits water.  

This type of fasting aims to give your gastrointestinal system a break from digesting food. This allows the body to focus on other processes, such as detoxification and healing. Given that it completely cuts down caloric intake, it can also create a sizeable calorie deficit, thus resulting in weight loss. 

Is Water Fasting Healthy?

If your fast lasts no longer than 24 hours per week and you don’t have any underlying health issues, you will likely face no dangers by doing a water fast. 

However, a more specific answer to this question depends on several factors, such as the fast’s duration, the individual’s health condition, and other lifestyle influences. 

Nevertheless, scientific literature suggests that water-only fasts can offer various psychological and physiological benefits, which we will discuss later.

Make sure that you approach it with caution and that you seek the guidance of a trained professional before attempting any extreme fasts. 

Moreover, if your main goal is to lose weight, remember that there are other less restrictive alternatives. A good example is intermittent fasting, which allows other calorie-free beverage options besides water. 

If you prefer a prolonged fast, you can try a 24-hour intermittent fasting or a 36-hour monk fast

Possible Benefits of Water Fasting

Here, we discuss several potential benefits of a water fast. It’s important to note that the scientific evidence supporting some of these claims is limited, and individual responses can vary. 

Studies report that water-only fasting brings about significant weight loss [1], reduces blood pressure [2], and improves glucose metabolism [1]

This form of fasting is also said to induce ketosis and autophagy, the process whereby the body destroys damaged cells and reduces inflammation [3]

There is also anecdotal evidence that a water fast will improve mental clarity and focus. It is also assumed that drinking only water for extended periods will help the body eliminate toxins.

Risks of Water Fasting

While water fasting has been proven to have potential benefits, there may also be various risks and side effects. It’s crucial to be aware of these not-so-desirable effects before considering or engaging in such a fast, especially if you’re planning to follow an extended water fast. 

Possible nutrient deficiencies

Prolonged water fasting can lead to insufficient essential nutrients, including macro and micronutrients. These nutritional deficiencies can lead to various health problems, such as fatigue, brain fog, and immune malfunctions. 

Electrolyte imbalances

Since water fasting completely restricts the intake of foods, there’s a high risk of not getting enough electrolytes such as sodium, potassium, and magnesium [4]. This can result in severe cases of electrolyte imbalances, thus producing side effects such as dizziness, weakness, and confusion [5]

Muscle mass loss

Another severe risk of water-only fasts is loss of muscle mass, which can happen if the fast continues for too long. Research suggests that around two-thirds of the weight lost during a water fast comes from muscle loss, while only one-third is fat loss [1].

Low blood sugar

There’s also a risk of low blood sugar levels due to extended hours of not eating. This can lead to dizziness or shakiness and, in more severe cases, might even lead to fainting. 

Avoiding food for long periods can also cause high levels of ketone bodies in the blood, thus resulting in starvation ketoacidosis [6]. This condition raises blood acidity, which can cause serious health problems if not controlled. 

May increase eating disorder risk

Prolonged water-only fasts also carry the risk of inducing eating disorders due to their restrictive nature. 

They can also result in short-term side effects such as irritability, sleep issues, and headaches [1]

Who Will Benefit from Water Fasting & Who Won’t

As we explained, water fasts have several potential health benefits, and you can consider trying it out if you’re generally healthy. For instance, if you want to lose some pounds, water fasting might give you a head start on weight loss. 

It can also help you kickstart new healthy eating habits while giving you a mental and physiological break from a less healthy diet. 

You can also follow a water fast if you are looking to improve conditions such as metabolic syndrome, insulin resistance, or high blood pressure. However, make sure that you discuss the pros and cons with your healthcare provider before starting the fast.

While there are considerable health benefits of water fasting, certain individuals, such as pregnant or nursing women and those who have a history of eating disorders, should approach water fasting with caution. 

It’s likely that the risks of water fasting outweigh its benefits for these individuals. 

Also, going without food can affect some people who are on certain medications. Moreover, those with a particularly demanding lifestyle will likely find it hard to comply with the challenges of water fasts. 

How to Water Fast

The basic rule of water fasting is simple: You should avoid food and any other beverage except water for the duration of the fast. However, there are some additional water-fasting tips you better follow to ensure safe and effective water fasting. 

Here are some of the essential guidelines:

  • Check with your doctor or nutritionist before starting your fast.
  • Choose a suitable duration, such as 24 hours once a week, to ensure higher compliance and to reduce the risk of side effects.
  • Keep yourself sufficiently hydrated.
  • Eat a healthy and balanced diet while not fasting to avoid any nutritional deficiencies.
  • Opt for mineral water to prevent any electrolyte imbalances.
  • Plan your fast to ensure you can stick to the fast and minimize physical and mental excursion.
  • Listen to your body. Break the fast immediately if you feel any serious side effects.

Water Fasting and Working Out

To decide if you can work out while you’re water fasting, you need to consider certain factors, such as the duration of the fast, your overall health, and endurance levels. For instance, if you regularly work out and are used to fasting, you might be able to do some light to moderate exercises during a short-term fast that is 24 hours or less. You can choose some gentle forms of exercise such as walking or yoga.

On the other hand, if you’re new to fasting or are not physically fit, it’s best to keep your exercises to a minimum during your fast.

Workouts are not generally recommended if you’re fasting for longer durations beyond 24 hours. Your body needs energy to work out, and your energy reserves will deplete when you don’t eat. 

How Much Weight Do You Lose in Water Fast?

Studies confirm that you can achieve a weight loss of a little less than 1 kilogram, or 2.2 pounds per week, during water fasting. However, studies also report that this weight is regained within three months of regular eating [1]

The amount of weight you lose during a water fast can vary widely depending on several factors, including the duration of the fast, your metabolism, and your body’s ability to retain water. 

Bottom Line

Water-only fasting is often associated with various claims of health benefits, potential risks, and side effects. Individual responses may vary, and you must pay attention to your body during the process. 

Short-term water fasting may be safe for some people. However, you need to consult a healthcare professional before trying prolonged fasting. Restricting food for extended periods without proper medical supervision can lead to adverse effects.

Disclaimer This article is intended for general informational purposes only and does not address individual circumstances. It is not a substitute for professional advice or help and should not be relied on to make decisions of any kind. Any action you take upon the information presented in this article is strictly at your own risk and responsibility!

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