Water fasting: Benefits, Weight Loss, and How to do it

Water Fasting Definition and Benefits

Water fasting refers to absolute abstinence from food consumption with the exception of pure water, which is consumed as much or as often as desired or necessary, in an environment of complete rest.

Voluntary abstinence from solid foods and some beverages for therapeutic, spiritual, or political reasons have been part of human society for centuries. The earliest account of therapeutic fasting can be traced back to the 5th century BCE when the ancient Greek physician Hippocrates advised abstinence from food or drink for those illnesses which he considered were the result of over-eating.

Water fasting, as a form of medical therapy, was introduced in America during the 19th century by Dr. Herbert Shelton. By the middle of the 20th century, it was being used in medically supervised inpatient settings for weight reduction in morbidly obese patients. However, water fasting as a dietary measure soon fell out of favor due to lack of efficacy and concerns for its safety.

Since the 1980s, the reemergence of research into fasting has elucidated potential physiologic benefits from water fasting that may be advantageous in the management of metabolic diseases, chronic inflammatory diseases, cardiovascular diseases, pain syndromes, and even psychosomatic conditions. Additionally, intermittent water fasting in conjunction with healthy diet and lifestyle changes was found to be an effective method of weight loss.

As with all forms of therapy, water fasting is not without risks. Adverse effects such as low blood pressure, dehydration, gastrointestinal upset, musculoskeletal pain, as well as possible worsening of some chronic diseases can be related to water fasting, especially if done incorrectly.

What Is Water Fasting?

Therapeutic water fasting is the complete abstinence from all substances except pure water in an environment of complete rest, according to Dr. Alan Goldhamer, the founder of TrueNorth Health Center. He further states that water fasting is one of the most potent tools available for assisting the body in healing itself. This video is an extended interview with Goldhamer on water fasting by health and lifestyle YouTuber Rich Roll.

What Are The Reasons For Water Fasting?

The primary reasons for water fasting are to improve one’s health through weight loss, detoxification of toxic chemicals stored in fat cells, strengthening of the immune system, reduction of inflammation, and autophagy.

Based on the Expert Panel Update of the 2002 Consensus Guidelines on Fasting Therapy by Dr. Françoise Wilhelmi de Toledo, water fasting has empirically documented beneficial effects in the following conditions. Some types of conditions potentially benefited by water fasting are indicated in the following diagram.

Diseases Benefited by Water Fasting

  • Endocrine, Nutritional, and Metabolic Diseases: Type II diabetes mellitus, obesity, metabolic syndrome, hyperlipidemia.
  • Diseases of the Cardiovascular System: Hypertension, coronary artery disease, heart failure.
  • Diseases of the Musculoskeletal System and Connective Tissue: Rheumatoid arthritis, spondyloarthropathy, degenerative diseases of the musculoskeletal system, chronic lower and upper back pain, fibromyalgia.
  • Diseases of the Nervous System: Migraine, chronic tension-type headache.
  • Psychological Disorders: Depressive mood disorder, psychovegetative exhaustion.
  • Diseases of the Digestive System: Functional gastrointestinal diseases, irritable bowel syndrome, inflammatory bowel disease, chronic constipation, fatty liver.
  • Diseases of the Respiratory System: Chronic bronchitis, chronic-obstructive pulmonary disease, asthma, chronic sinusitis, allergic rhinitis, allergic diathesis.
  • Diseases of the Urogenital System: Recurrent cystitis, dysmenorrhea and premenstrual syndrome, climacteric syndrome, fertility disorders.
  • Diseases of the Skin: Neurodermatitis, psoriasis, urticaria, acne.

Outside of therapeutics, water-only fasting is part of Jainism, an ancient Indian religion in which only boiled water and no food is consumed for one to two weeks during birthdays, anniversaries, festivals, and on holy days.

Water fasting has been used as a form of protest. An example of this is the Irish hunger strike of 1981, during which members of the Irish Republican Army consumed nothing but water and salt in order to oppose British government policies.

How To Perform Water Fasting?

Water fasting is performed by determining if you are a candidate for the process, completing a pre-fast medical evaluation, preparing your body for the fast, creating an environment conducive to the fast, incorporating key behavioral changes during the fast, deciding when to end the fast, and restoring the body in a post-fast period. Whether done intermittently or for a prolonged time, water fasting requires a dietetic protocol that is ideally guided by clinicians to ensure safety and efficacy.

These are the steps to do before carrying out a water fast.

6 Steps Before Water Fasting

Step 1: Determine if you are a candidate for water fasting

Although water fasting can be attempted by everyone, some notable exceptions exist. According to a study by Dr. Alda Attinà and Dr. Claudia Leggeri from the School of Specialization in Food Sciences in Rome, the following patients should not attempt water fasting.

  • Children and adolescents have increased nutritional requirements for growth and development, and as such fasting can have negative psychological and physiologic consequences.
  • The Elderly(75 and older) should refrain from fasting due to the increased risk of complications.
  • Pregnant and Breastfeeding women have precise energetic and nutritional requirements, that if eliminated even for a short period can be detrimental to both the mother and child.
  • Those with an active infection, at risk of repetitive infection, or who are persistently immunocompromised should refrain from water fasting.
  • Diabetes mellitus is a contraindication to fasting according to the American Diabetes Association, even though proponents of water fasting argue that fasting helps promote insulin sensitivity and glucose control along with modest decreases in body weight, although little evidence exists to support these arguments.
  • Anorexia nervosa and other eating disorders preclude the use of water fasting.
  • Advanced diseases of cerebrovascular, renal, and hepatic systems serve as contraindications.

Step 2: Complete a pre-fast medical evaluation

A pre-fasting medical evaluation should be completed. This should include a comprehensive evaluation of an individual’s health as well as an analysis of any prescribed medication, such as steroids, contraceptives, antihypertensives, or anticonvulsants, which may be influenced by caloric restrictions.

Step 3: Prepare your body for the fast

If an individual is a good candidate for water fasting, the next recommended step is to prepare the body. The doctors from the School of Specialization in Food Sciences in Rome recommend the adoption of a balanced diet rich in plant-based foods. This includes whole grains, fresh fruits, and vegetables, legumes, nuts, and olive oil. Avoidance of processed and hypercaloric meals, soft drinks, caffeinated drinks, and alcohol is recommended.

Step 4: Create an environment conducive to a water fast

Before beginning a water fast, it is important to have a comfortable environment and a plentiful supply of good quality drinking water. A total water intake of 1.8 L/24h for all individuals is recommended by Prof. Lawrence E. Armstrong of the Human Performance Laboratory and Department of Nutritional Sciences at the University of Connecticut.

Step 5: Incorporate key behavioral changes during the fast

During the fast, non-stressful physical activity, behavioral and lifestyle modifications, and relaxation techniques are recommended.

  • Aerobic exercise, gymnastics, and/or yoga should be added to the water fast, and their intensity adjusted to the individual’s condition.
  • Behavioral introspection and lifestyle modifications aim to help the person fasting identify possible causes of the conditions they wish to improve, reinforce their motivation for fasting, and prevent lapses in the fasting regimen.
  • Relaxation therapies such as muscle relaxation, breathing techniques, meditation, and visualization can be helpful in minimizing possible unpleasant effects of water fasting and in maintaining the fast.

During the fast, water can be drunk ad libitum, meaning as much or as often as desired or necessary.

Step 6: Decide when to end the water fast

Ending, or “breaking” the fast is highly individualized. The decision to end the fast is based on an individual’s physical health, psychological state, and personal circumstances. Alternatively, medical indications for discontinuing fasting according to the Expert Panel Update of the 2002 Consensus Guidelines on Fasting Therapy include the following.

  • Non-compliance, which refers to not adhering to the water fast regimen.
  • The onset of serious or even life-threatening arrhythmias.
  • Stomach and reflux problems.
  • Severe electrolyte abnormalities.
  • Circulatory or cardiac depression with decreased heart rate and blood pressure.

This diagram shows the first six steps to take before starting a water-based fast.

Step 7: Post-fast period

After the water fast, slow and gradual reinstitution of feeding with whole, natural foods is essential. Adopting a long-term regular, balanced diet and appropriate physical activity is necessary to maintain the positive effects achieved through water fasting.

The goal of the entire water fasting process is to create an environment in which the body can heal itself. However, it is important to remember that monitoring and supervision during the fasting process are necessary to ensure efficacy and safety.

What Are The Common Mistakes Of Water Fasting?

The common mistakes of water fasting include starting too fast, insufficient preparation, unrealistic goals, not drinking enough water, and not implementing key behavior changes. Not paying attention to these issues can decrease the effectiveness of water fasting and can even have adverse effects on the faster’s well-being.

Common Mistakes of Water Fasting

  • Starting Too Fast: The biggest mistake one can make with water fasting is to start off fasting too drastically. Water fasting is a major decision that should be given adequate consideration and be gradually undertaken. Being unprepared, whether mentally, physically, or emotionally for a water fast will only lead to failure.
  • Insufficient Preparation: Undertaking water fasting without consultation and pre-fasting evaluation is another mistake. These steps are essential in ensuring that water fasting is the right choice for an individual and that the fast will not endanger their health in any way.
  • Unrealistic Goals: Setting unrealistic goals is a mistake. Water fasting should be approached gradually, especially by those who are new to it. Starting with intermittent feeding and fasting periods of short duration and gradually prolonging the water fasting intervals to several days is the best approach.
  • Not Drinking Enough Water: Not consuming enough water during your fast is a mistake. Water is essential to the fast, and inadequate intake can have dangerous health-related consequences.
  • Not Implementing Key Behavior Changes: Lastly, not incorporating exercise, behavioral and lifestyle modification, and relaxation techniques into the fasting period, as well as beyond it, will result in submaximal results.

What Are The Health Benefits Of Water Fasting?

The health benefits of water fasting refer to the ways in which it can be beneficial to an individual’s physical well-being and includes the following benefits.

  • Lowers blood pressure
  • Improves insulin
  • Regulates leptin sensitivity
  • Decreases chronic diseases

1. Lowers Blood Pressure

Water fasting can help reduce blood pressure. Medically supervised water-only fasting appears to be a safe and effective method of lowering blood pressure according to a study entitled “Medically supervised water-only fasting in the treatment of hypertension” published in the Journal of Manipulative and Physiological Therapeutics by Dr. Alan Goldhamer. The effects of this water fast on the blood pressure, weight, and body mass index (BMI) of patients are graphed below.

Impacts on Body of Water Fasting

The exact mechanisms are unclear, but fasting appears to reduce sodium levels, decrease cholesterol, and help control diabetes which are all risk factors for elevated blood pressure.

2. Improves Insulin

Water fasting can induce physiological responses which increase insulin sensitivity. Water-only or very low calorie (less than 200 kcal/day) fasting can enhance insulin’s actions and improve glucose utilization, which are mechanisms often abnormal in diabetes and metabolic syndrome according to a study entitled “Fasting: Molecular Mechanisms and Clinical Applications” by Dr. Valter Longo. However, the mechanisms for improved peripheral insulin sensitivity and glucose tolerance are unclear.

3. Regulates Leptin Sensitivity

Water fasting increases Leptin sensitivity. A study entitled “The influence of fasting and energy-restricted diets on leptin and adiponectin levels in humans’ by Dr. Hamed Varkaneh Kord from the National Nutrition and Food Technology Research Institute of Iran found that water fasting or very low-calorie fasting elicits a significant reduction in serum leptin concentrations, which increases tissue sensitivity to leptin.

Leptin is a hormone that modulates appetite and can be used as a marker for inflammation. Its suppressed levels indicate a state of suppressed inflammation and can improve cell response to insulin’s actions. The exact mechanism or consequences of this reaction have yet to be determined, but it is clear that alterations in body fat mass as a result of water fasting play a role in the regulation of leptin levels and sensitivity.

4. Decreases Chronic Diseases

Water fasting can improve and alleviate chronic diseases such as cancer, cardiovascular disease, autoimmune disease, Diabetes Mellitus, and neurocognitive decline according to the Institute for Functional Medicine. They suggest that water fasting improves metabolic health through improvements in insulin sensitivity, blood lipid markers, hypertension, and inflammatory markers which all play a role in the progression of chronic disease.

What Are The Health Risks Of Water Fasting?

The health risks of water fasting include dehydration, orthostatic hypertension, the worsening of other health conditions, losing the wrong type of weight, and a long list of moderate issues like headaches and back pain.

Risks to Human Body of Water Fasting

A study by Dr. John Finnell from the AOMA Graduate School of Integrative Medicine in Texas evaluated the safety of fasting through a medical history review of adverse events during medically supervised, water-only fasting in 768 cases. Among the most common adverse health effects related to water fasting were:

  • Fatigue - 48.2%
  • Insomnia - 33.5%
  • Nausea - 32.2%
  • Headache - 30.1%
  • Hypertension - 29.2%
  • Presyncope - 28.3%
  • Dyspepsia - 25.9%
  • Back pain - 25.7%
  • Pain in the extremities - 16%
  • Abdominal pain - 15.1%
  • Diarrhea - 14.2%
  • Vomiting - 12.5%
  • Arthralgia - 12.1%
  • Palpitations - 11.4%

Overall, the authors suggest that the adverse effects to one’s health experienced during medically supervised water-only fasting are mild to moderate in nature and well-known. The following are some of the more important risks to be aware of.

1. Causes Dehydration

As 20-30% of water is derived from the food we consume, dehydration can set in quickly if an adequate amount of water is not consumed to substitute for dietary water. Dehydration can manifest itself by symptoms and signs of thirst, lethargy, headache, confusion, dizziness, sunken eyes, and dry skin and mucous membranes.

2. Creates Orthostatic Hypotension

Orthostatic hypotension and syncope refer to a significant drop in blood pressure followed by loss of consciousness occurring upon standing up from a supine position. The most common cause of orthostatic hypotension is dehydration which can be induced by water fasting.

This video explains how Orthostatic Hypotension occurs and was produced by the patient advocacy group Treat Neurogenic Orthostatic Hypotension Now Coalition.

3. Worsens Several Health Conditions

Several health conditions can be exacerbated by and are not conducive to water fasting. The most notable example is Gout. Gout is a condition in which high blood levels of uric acid cause deposits of uric acid crystals to accumulate in joints leading to acute episodes of painful inflammation.

In water fasting, the increased cell breakdown leads to excess production of uric acid which can precipitate gout. Therefore, patients with gout should not participate in water fasting.

Additionally, conditions such as active infection, diabetes mellitus, anorexia nervosa, and other eating disorders, as well as advanced diseases of cerebrovascular, renal, and hepatic systems can be worsened by water fasting.

4. Loses Wrong Type Of Weight

Utilizing water for weight loss via water fasting, if approached incorrectly, can lead to not only the breakdown or metabolism of fat cells but protein from muscles and visceral organs. This type of weight loss is “inappropriate” as it leads to muscle and wasting.

Therefore it is essential that water fasting be done in a comfortable and restful environment without outside stressors. Stress may increase the energy requirements for the body, which may require the body to break down its protein stores from muscles and internal organs in addition to fats.

How Long Can Someone Perform Water Fasting?

Someone can perform water fasting for as short as less than a day to up to 40 days. But the duration of water fasting depends on an individual's goals, physical and mental health, and experience with water fasting. Those new to fasting should start with shorter fasts and ease into the longer practice.

Time-Restricted Feeding (TRF) and Intermittent Fasting (IF) are relatively short-duration water-only fasts ranging from half a day to three days. They are better choices for those new to this regimen. Prolonged Fasting (PF) should be reserved for therapeutic purposes and should only be undertaken under medical supervision.

How Long Can You Water Fast

1. Short-term Water Fasting (12-24 Hours)

Time-Restricted Feeding (TRF) represents short-term water fast during which food intake is restricted to a time window of 8–12 hours or less every day.

Dr. Corey A. Ryders from the University of Colorado Anschutz Medical Campus in his study on “Effectiveness of Intermittent Fasting and Time-Restricted Feeding Compared to Continuous Energy Restriction for Weight Loss” stated that TRF can be an effective strategy to reduce the overall caloric intake in those attempting to lose weight without having to involve caloric restriction.

Direct medical supervision is usually not necessary for short-term water fasting, but medical help should be available if problems arise.

2. Long-term Water Fasting (1 - 3 Days)

Longer periods of water-only fasting can be observed during Intermittent Fasting (IF). During intermittent fasting individuals alternate between several (approximately 2-3) days of water fasting and days of normal caloric intake.

Ruth E. Patterson and Dorothy D. Sears in their study on the Metabolic Effects of Intermittent Fasting found that intermittent fasting provides a broad range of benefits from the reduction of oxidative stress and blood sugar levels to improved memory and cognitive function.

Long-term water fasting is associated with health risks. Although close medical supervision may not be necessary, one should ensure they can reach a doctor quickly if problems develop.

3. Risky Long-term Water Fasting (3+ Days)

Prolonged fasting (PF) refers to fasting for an extended period, from 3 to even 40 days. This type of water-only fasting is reserved for therapeutic purposes and should not be undertaken without medical supervision.

Prolonged fasting can pose serious dangers to one’s health such as life-threatening dehydration, fainting and falls, dangerous arrhythmias, as well as significant reductions in heart rate and blood pressure.

As such, eligibility for prolonged fasting, how it will be carried out, and how long it should be done for should be decided in consultation with a medical professional. Furthermore, risky long-term water fasting should only be done under proper medical supervision.


  • Nina J

    Thank you for this Article on Water Fasting.
    In 2018 at 58 I was grossly over weight post Menopausal and depressed.
    After 21 days Water Fasting I began to feel more comfortable.
    After 10 days on Water Melons and avocado’s more benefits.
    Life since has been complex. IBS Reflux pain in upper abdomen upon eating, and just getting older needing adjustment to less food.
    I embark once again into
    Water Fasting for 15 days.
    I have not felt well a long time. Discovered my body does best on light fruits . I am working to be disciplined. Not a strength.
    Your You Tube interviews on True-north with Goldhamer is comprehensive and educational.
    I learn by doing best. Yet some facts as knowledge going in, is helpful.
    My daughter an adult now is managing her MS RR with Vegetable Juices, Papaya fruits in mass , and when well, cooked Salmon.
    Each of us with individual reasons, find our Western Culture of Foods, trigger symptoms, and cause pain.
    Do people over Time become stricter about what they eat after Water Fasting long term ? Does the body crave fat and sugar & salts less over time after long term Fasts ?
    Does Water Fasting help IBS that has become chronic?
    What generally is the meaning behind why the body as it ages tolerates less, and less foods eaten years before?
    Are Doctors in The States now more open to benefits of Water Fasting longer Term ?
    Thank you for the opportunity to leave comments here. Warm regards

  • Lindiwe Nhleko

    Thank you so much for the information

Leave a comment

Please note, comments must be approved before they are published