Mya Care Blogger 02 Jan 2024

A water fast is a type of fast that involves consuming only water for the period of the fast, which usually ranges from 24 to 72 hours. People practice water fasting for religious, spiritual, or health reasons, such as weight loss, detoxification, or disease prevention. If you are considering water fasting, then it is important to understand the benefits as well as the risks and how to water fast safely and effectively.

In this blog, we will answer some of the most common questions about water fasting and provide tips and guidelines for those wanting to try it.

Water Fasting Benefits

People try water fasting primarily to improve their health. In fact, several studies have correlated water fasting with some compelling health benefits, such as:

  • Stimulating cell regeneration via autophagy, a process that supports your body in breaking down and recycling old or damaged parts of your cells. Autophagy may protect against various diseases, such as cancer, neurodegenerative disorders, infections, and metabolic conditions.
  • Enhancing human growth hormone (HGH) production, a hormone that stimulates cell growth and regeneration, preserves muscle mass, and burns fat for energy. HGH levels may increase significantly during water fasting, especially in the first few days.
  • Lowering blood sugar and insulin levels, which may improve insulin sensitivity and reduce the risk of type 2 diabetes and its complications.[1] Water fasting may also lower blood pressure and cholesterol levels, which may benefit cardiovascular health.
  • Reducing inflammation and oxidative stress, factors linked to aging and chronic diseases. Water fasting may modulate the expression of genes and proteins involved in inflammation and antioxidant defense.
  • Promoting weight loss, through creating a calorie deficit and shifting the metabolism to burn fat for fuel. Water fasting may also suppress appetite and hunger hormones, making it easier to persist with a reduced-calorie diet after the fast.
  • Increasing longevity, by triggering biological processes that slow down aging, prevent chronic diseases, and improve metabolic function.[2]

However, water fasting has several risks and can be very dangerous if followed for too long or without proper guidance. These are discussed in the following sections.

Stages of Water Fasting: How to Water Fast Safely

Water fasting is not suitable for everyone and should be done with caution and medical supervision. Some people should not water fast at all, such as those who are:

  • Pregnant or breastfeeding
  • Underweight
  • Diabetic or have a similar health condition
  • Physically dependent on medications that require food

Choose a time to fast when you are not under stress, have no social obligations, and can rest and relax. Avoid fasting during extreme weather conditions, such as intense heat or cold.

Preparing for the Fast

If you have never fasted before, it is a good idea to spend 3–4 days getting your body ready to go without food. Eating smaller portions at each meal, fasting for part of the day, and switching towards a plant-based whole-food diet can be helpful in this regard. Avoid processed foods, added sugars, caffeine, and alcohol. This will help you adjust to the hunger and cravings that may arise during the water fast.

During the Fast

While fasting, you need to avoid eating or drinking anything besides water. You should drink at least 2 to 3 liters of water daily, preferably mineralized water, to stay hydrated and replenish your electrolytes.

You might feel your mood and energy levels rise and fall during the fast, as well as hunger pangs. These symptoms are usually transient and pass within an hour or two. You may need to nap in between.

Breathe: You may want to practice deep breathing exercises to lower possible stress associated with not eating, keep your energy levels up, and feel clear-headed and more refreshed during the fast.

Be Aware of Ketosis: During the water fast, your body will undergo several metabolic changes. Your body will typically deplete its glycogen stores (the main source of energy from carbohydrates) in around 12 to 16 hours of fasting. This will trigger a state known as ketosis, where your body burns fat for fuel instead of glucose.[3]

Ketosis can have several benefits, such as

  • Suppressing your appetite
  • Enhancing your cognitive function
  • Improving your blood lipid profile

However, ketosis can also cause some side effects, such as bad breath, constipation, headache, fatigue, and nausea. These symptoms usually pass with rest or drinking more water. If you feel too overwhelmed, end the fast.

Monitor for Signs of Dehydration, such as thirst, dry mouth, headache, dizziness, fatigue, weakness, vomiting, muscle cramps, or fainting. If you experience any of these, drink more water, add some salt to your water, or end the fast.

Breaking the Fast

Breaking a water fast is as important as the fast itself. You should not rush back to your normal eating habits, as this can shock your system and cause digestive distress, such as bloating, cramping, diarrhea, or vomiting. You should also avoid binge eating, which can undo the benefits of fasting and cause weight gain.

This is especially true if participating in a 7-day water fast, as you can risk refeeding syndrome if you start eating lots of food too soon afterward.

The best way to break a water fast is to gradually reintroduce foods, starting with easily digestible liquids and soft foods. Here are some tips for what to eat after a water fast:

  • Drink a glass of water with some lemon juice or apple cider vinegar before your first morsel of food. This will help stimulate your digestive enzymes and prepare your stomach for a meal.
  • Make a bone or vegetable broth to drink as the first meal. This will provide some nutrients and electrolytes, as well as soothe your gut lining.
  • Introduce fruits and vegetables into subsequent meals. It can be a good idea to consume a stew at the second mealtime to restore your gut.
  • Gradually increase and resume consuming other foods as part of your diet. Consume in small portions as you do this, and continue to avoid overly processed foods until you are back on a completely plant-based diet again. You might be a lot more sensitive to some foods depending on how long you fasted. Avoid consuming foods that cause a reaction.
  • Continue to drink plenty of water.

You can resume your normal diet after a few days. Keep in mind that your body and digestive tract will be a lot cleaner after fasting and that you may not respond the same way to certain foods or beverages. This is not a bad sign. Instead, it shows you can better sense a reaction to a particular food. A similar principle is used for people on an elimination diet who are suffering from allergies or sensitivities and struggle to pinpoint the triggering food.

How Long Can You Water Fast for?

Most people choose to water fast for 2-3 days. Studies have shown that healthy individuals may undergo 7-day water fasting without an issue, provided fasting is not contraindicated.[4] Participants showed the following water fasting results after 7 days:

  • Reduced perceived stress
  • Enhanced sense of well-being
  • Weight loss
  • Better hydration and urinary health
  • Less body acidity
  • Lower blood sugar levels
  • Reductions in blood sodium and blood pressure

The downsides to the study were very minimal and included depletion of calcium and magnesium stores (yet not deficiency), as well as kidney protein sparing. Any longer than 8 days may begin to border on starvation and push the body towards a less desirable state of being.

Water Fasting Dangers: Potential Risks and Side Effects

Water fasting is not without risks and side effects. These include:

  • Losing muscle mass, as your body may break down muscle tissue for protein and energy. This may lower your metabolic rate and make it tougher to maintain or lose weight in the long term.
  • Experiencing hunger, cravings, irritability, mood swings, or boredom. These may affect your mental and emotional well-being and make it difficult to persist with fasting.
  • Having low energy, reduced physical performance, and impaired cognitive function. These may affect your daily activities, work, or school.
  • Developing nutritional deficiencies, especially if you fast for longer than 72 hours or do it frequently. You may miss out on essential vitamins, minerals, and antioxidants that your body needs for optimal health.
  • Triggering or worsening eating disorders, such as anorexia or bulimia. Water fasting may become a form of self-starvation or binge-purge cycle, which can have serious consequences for your physical and mental health.

Ketoacidosis is a rare yet serious condition that can occur due to prolonged insufficient availability of glucose as the body’s primary energy source.[5] It happens after prolonged ketosis, often due to starvation, which causes excessive blood acidity. Ketoacidosis can cause symptoms such as nausea, vomiting, abdominal pain, confusion, and, in severe cases, coma. It can also lead to dehydration, electrolyte imbalance, and organ damage. Ketoacidosis from fasting requires immediate medical attention and treatment, which may include intravenous fluids, electrolytes, insulin, and glucose.

Who Should Not Water Fast? Side Effects, Contraindications, and Safety Considerations

As mentioned above, water fasting is not recommended for people who have certain medical conditions or take medications that require food. Additionally, water fasting is not advised for people who are:

  • Under 18 or over 75 years old, as they may have different nutritional needs and higher risks of complications.
  • Underweight or have an eating disorder. Water fasting can worsen their nutritional status and psychological condition.
  • Trying to conceive, as water fasting may affect fertility and hormonal balance.
  • Pregnant or breastfeeding. Water fasting can deprive the mother and the baby of essential nutrients and calories, which can affect their health and development.
  • Fighting an infection or have a compromised immune system. Water fasting can impair the immune response and increase the risk of complications.
  • Preparing for or recovering from surgery or a medical procedure. Water fasting can interfere with the healing process and the medication effects.
  • Diabetic or taking insulin or other blood sugar-lowering medications. Water fasting can cause hypoglycemia, which is a dangerous drop in blood sugar levels.
  • Diagnosed with heart disease or taking blood pressure or heart medications. Water fasting can cause electrolyte imbalance, which can affect the heart rhythm and blood pressure.
  • Patients with kidney disease or taking diuretics or other kidney medications. Water fasting can cause dehydration, which can worsen kidney function and increase the risk of kidney stones.
  • Living with gout or taking gout medications. Water fasting can increase uric acid levels, which can trigger gout attacks.

Does Water Fasting Affect the Menstrual Cycle?

Fasting is known to lower female reproductive hormones, which may be problematic during weeks 3 and 4 of the menstrual cycle for some women. According to certain sources, some women may prefer to fast during weeks 1 and 2 of their menstrual cycles, when they have the most energy[6], while others may not notice any difference.

Does Water Fasting Cause Diarrhea?

Water fasting can cause diarrhea in some cases, yet it is not very common unless you are unwell, using electrolytes on the fast, or break the fast with a large, rich meal (fat-heavy, high in sugar, or spicy). Diarrhea during fasting can be dangerous, as it can lead to dehydration, malnutrition, and electrolyte imbalance. Therefore, if you experience severe diarrhea while fasting, you should end your fast and drink plenty of water and electrolyte-replacement drinks.

Frequently Asked Questions

Is it Safe to Work Out While Water Fasting?

While beneficial for your health, working out on a water fast may not be the best idea. Exercise increases energy expenditure, appetite, and muscle breakdown, which may make water fasting difficult, unpleasant, and undermine the benefits.

However, light exercise while on the water fast might help to keep your mood and energy levels stable, depending on what you choose to do. Gentle exercise can help lower stress and has benefits that overlap with fasting. The body moves into a state of ketosis to provide energy during periods of starvation, where we would be encouraged to get physically active in search of food.

Considerations include your level of health, your metabolism and the kind of exercise you prefer to do while fasting, as well as the length of the fast. If you want to exercise during a water fast, here are some tips to follow:

  • Choose low-intensity and low-impact activities, such as walking, yoga, stretching, or light cycling. Avoid high-intensity and high-impact exercises, such as running, jumping, lifting weights, or HIIT.
  • Listen to your body and stop if you feel dizzy, faint, nauseous, or weak. Do not push yourself beyond your limits or ignore any warning signs.
  • Drink enough water to prevent dehydration, and try not to break a sweat while exercising or lose fluids excessively.

Can You Take Medication While Water Fasting?

One should not take medications or supplements while on a water fast, as these can potentially interfere with the process. This includes antibiotics, painkillers, cough syrups, antacids, multivitamins, caffeine, or energy drinks.

If on prescription medications, it is important not to stop your prescription in order to try fasting, especially if the medication induces physical withdrawal effects. These effects may even occur in those taking their medication while trying to fast, which is why those with health conditions should avoid fasting.

Can I Chew Gum While Water Fasting?

While chewing gum is technically not a form of eating, gum contains a lot of additives as well as sugars that can defeat the point of water fasting. Chewing gum can impact the metabolic shift towards ketosis, and this might also increase your hunger and decrease the benefits.

Chewing gum also causes the stomach to produce more stomach acid, as chewing acts as a signal for digestion[7]. Chewing gum for a prolonged period without food can relax the gastric sphincter and may cause the lining of the esophagus and stomach to suffer, which can increase the risk for ulcers and gastroesophageal reflux[8]. While chewing gum may lower the risk of reflux after a meal and may help relax the gut when fasting prior to gastrointestinal surgery, it is not likely to be beneficial during a 3-day or longer fast or to use for fasting on a regular basis.


Water fasting involves a type of fasting where one only consumes water for the fast’s duration. It may have several health benefits, such as stimulating cellular growth, regeneration, and renewal, lowering blood sugar and insulin levels, decreasing stress and blood pressure, reducing inflammation and oxidative stress, and promoting weight loss. However, it also has some potential risks and side effects, such as losing muscle mass, experiencing hunger and mood changes, having low energy and cognitive function, developing nutritional deficiencies, and triggering or worsening eating disorders.

Water fasting is not suitable for everyone and should be done with caution. If you want to try water fasting, you should prepare your body for the fast, choose a time when you can rest and relax, drink enough water, monitor yourself for signs of dehydration, and break the fast gently and gradually. You should also avoid exercising intensely and taking medications or supplements that may break your fast or interfere with your metabolism. Avoid fasting if you have certain medical conditions or take prescription medications that require food.

Water fasting is not a magic bullet or a quick fix for your health problems. If done in a safe and effective way, factoring expert advice and following the guidelines and water fasting tips, it can be used as a tool to improve your health and well-being. It is advisable to consult a doctor before starting a regimen that involves prolonged fasting.

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