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What Is Water Fasting? Benefits, Risks And More




Water fasting is a typical type of fasting in which you consume only water for a set length of time. Although fasting has long been performed for religious and spiritual reasons, it has recently become a hot wellness fad, with some suggesting that it can help with weight loss and overall health. But is it effective, and most importantly, safe?

Continue reading to learn more about water fasting, including what it is, how it works, and whether it’s worth trying.

What Is Water Fasting?

Water fasting is a practice in which you abstain from all food and only drink water for multiple days at a time.

Some people undertake water fasting to improve or preserve their health. Other reported health benefits include reduced inflammation, reduced oxidative stress, and improved lipolysis, which is the breakdown of fat.

Who Should Not Water Fast?

Kaytee Hadley, a functional medicine dietician based in Richmond, Virginia, advises against water fasting for everyone. Hadley emphasizes that the following groups should avoid water fasting:

  • Children
  • Teenagers
  • People who are pregnant or breastfeeding
  • Individuals with certain health conditions, including gout or insulin-dependent diabetes
  • Adults over 75 years of age
  • People with a history of disordered eating

It’s also best to talk to a doctor before trying prolonged fasts, as going 24 hours or more without food can be dangerous for some people.

How Does Water Fasting Work?

As the name implies, water fasting is limiting your meal intake and drinking solely water. Here’s a closer look at some of the most frequent methods and what to eat when it’s time to break your fast.

Water Fast

There are numerous ways to try water fasting, which vary depending on the length of your fast. 16/8 fasting is a popular, more manageable variation of intermittent fasting in which you limit your meal consumption to an eight-hour window each day and drink just water for the remaining 16 hours.

You can also try water fasting for whatever length of time that suits your own tastes and schedule. Fasting over longer periods of time (such as 24 to 72 hours) can be risky for some people and is generally not suggested unless prescribed by a doctor.

To stay hydrated during fasting, drink plenty of water. It is also generally recommended to avoid rigorous activity and instead engage in gentler hobbies such as yoga. If your profession is physically demanding, you should plan your fasts around your timetable to avoid unwanted side effects.


Following a balanced and nutritious food after your fasting period is essential. Try to eat nutrient-dense foods such as fruits, vegetables, nuts, and legumes, and be sure to get adequate protein, especially from plant-based sources or fish, to help maintain lean body mass. Staying hydrated by drinking enough of water might also benefit your general health after your fast.

It may also be beneficial to opt for smaller, lighter meals immediately after a fast before progressively introducing larger meals. This is especially crucial for prolonged fasts because it can help prevent refeeding syndrome, which is a dangerous illness caused by fluid and electrolyte imbalances after a period of famine.

Potential Benefits of Water Fasting

When done correctly, water fasting may provide some health benefits, particularly in terms of cardiometabolic health, insulin sensitivity, and autophagy, according to Ro Huntriss, a registered dietitian based in London and chief nutrition officer at Simple, an intermittent fasting app. “Some also suggest that water fasting promotes mental clarity and focus,” according to Huntriss.

Here are some of the potential benefits, according to experts.

May Improve Blood Sugar Levels

Melanie Murphy Richter, a functional dietitian located in Santa Monica, California, believes that fasting may assist lower blood sugar levels by increasing insulin sensitivity. This could help your body use insulin more efficiently, which is the hormone responsible for regulating blood sugar levels. “This may help with conditions like prediabetes and type 2 diabetes,” adds Murphy Richter.

A 2023 study in Nutrition Reviews discovered that prolonged fasting (defined by ingesting little to no caloric meals or beverages) lasting five to 20 days could lower fasting blood sugar and insulin levels while reducing insulin resistance. Researchers also discovered that it could lower levels of hemoglobin A1c (a sign of long-term blood sugar control) in persons with normal blood sugar levels. Similarly, a small, recent study found that prolonged fasting may be more beneficial than short-term fasting in boosting insulin release and glucose tolerance (or the body’s response to sugar).

May Increase Weight Loss

According to Murphy Richter, fasting with water can help you lose weight and fat. She adds that it can also assist break weight reduction plateaus by inducing ketosis, a metabolic state in which the body burns fat for fuel rather than sugar. “This produces ketones, which serve as an alternative energy source for the brain and other organs,” according to Murphy Richter.

In one small trial, individuals dropped an average of more than 13 pounds and had significant decreases in body fat after completing an eight-day water fast.

However, research suggests that, while fasting can help you lose weight, it can also cause you to lose muscle mass. This could be attributed to the accelerated breakdown of muscle proteins that happens after extended fasting.

Promotes Autophagy

According to Murphy Richter, one of the most significant benefits of water fasting is its capacity to initiate a process known as autophagy. This process occurs when the body begins “to clean out old and dysfunctional cells, making way for the generation of new, healthier cells,” according to her.

According to research, autophagy may help reduce the aging process and extend longevity. It may also help prevent neurodegenerative illnesses and metabolic disease.

Could Help Protect Heart Health

According to Murphy Richter, fasting can reduce various risk factors for heart disease, including lowering blood pressure in hypertensive persons and improving cholesterol by lowering LDL (bad) cholesterol while boosting HDL.

According to one 2021 study, water fasting could considerably improve blood pressure levels in persons with hypertension, or high blood pressure. However, researchers stated that additional research is needed to understand the impact of fasting on hypertension.

Risks of Water Fasting

Though water fasting may have certain benefits, it is unclear whether these benefits are sustained over time. In fact, one assessment found that the metabolic benefits of prolonged fasting disappeared three to four months after the fast was terminated, even when weight loss was maintained.

Furthermore, water fasting may pose a number of dangers. “Skipping meals means missing out on vital nutrients that sustain our bodies,” said Hadley. She points out that this can result in a number of dangerous short-term negative effects, including:

  • Low blood sugar
  • Sudden drops in blood pressure
  • Fatigue
  • Dizziness
  • Nausea

“When done long term, water fasting can be dangerous and even fatal without medical supervision because of nutrient and electrolyte imbalances,” said Hadley. As a result, it’s best to see a health care expert before attempting fasting, and stop if you suffer any of the symptoms listed above.

If you want to try water fasting, Johannes Uys, a general practitioner at Broadgate General Practice in London, recommends starting slowly. “Beginners can get used to longer water fasts of 24 to 72 hours by first fasting for shorter periods before slowly building themselves up until they can reach 24 hours without eating,” Dr. Uys said. “This is especially critical if you are used to eating enormous amounts regularly.

A few other tips to help you get started with water fasting include:

  • Gradually reduce your intake: “Start by reducing your portion sizes, cutting out snacks and slowly eliminating the number of meals you eat throughout the day,” adds the doctor. “Some people find that this is enough for them to get the results they’re looking for, so a taper is a great way of gradually testing the waters until you find a method that works for you.”
  • Drink more water: “A lot of people are surprised to find out that we receive around 20% to 30% of our daily hydration from the food we ingest,” Dr. Uys said. He emphasizes that while fasting, it is vital to drink more water than usual in order to compensate for the water lost from food consumption.
  • Talk to a doctor: If you have diabetes or another health condition that affects your gut, metabolism or heart, checking in with a doctor first can help reduce some of the risks associated with fasting, according to Dr. Uys.

Is Water Fasting Safe?

While water fasting may have a number of benefits, Huntriss and Murphy Richter both warn that it is not for everyone. “The safety of water fasting depends on various factors, including individual health conditions and medical history,” Murphy Richter, a physician, explains. Water fasting may not be suitable for pregnant or breastfeeding women, elderly adults, those at risk of eating problems, or people with specific health concerns, such as immunodeficiency disorders.

Water fasting can also disrupt the body’s water-mineral balance, according to Shinta Galej, a renal dietitian based in New York. According to Galej, this might lead to complications such as hyponatremia (low sodium levels), which can be serious or even fatal. According to Galej, water fasting can also raise uric acid levels, which is dangerous to people who have kidney illness or gout.

Also, keep in mind that lengthy fasting durations (range from 24 to 72 hours) might be deadly if not done under medical supervision. They can also cause your body to retain excess fat in response to starvation, negating many of fasting’s potential health benefits. As a result, it is preferable to stick to shorter fasts unless directed by a doctor.

When to See a Doctor

If you have any underlying health conditions, such as diabetes, see your doctor before attempting to fast on water. If you are using any drugs or supplements, consult your doctor before fasting. Some drugs and supplements must be taken with food to avoid stomach irritation or nausea, and missing meals may increase the risk of electrolyte imbalances if you are taking medications for heart disease or high blood pressure.

Water fasting may have various advantages, including enhanced weight loss, improved heart health, and better blood sugar control. However, it is not suitable for everyone and, in rare situations, can be hazardous. If you’re interested in trying water fasting, talk to a doctor or registered dietitian to determine if it’s a safe option for you and whether it can help you meet your goals.

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