Water Fasting: Benefits and Risks

Water fasting is a type of fasting method that permits drinking only water without any food for the duration of the diet. Usually, water fasting is followed as a weight loss or detox technique. Nevertheless, this ancient diet approach that dates back to ancient Greece may pose serious health consequences if not followed under medical supervision.

Water fasting may have limited short-term benefits if it is followed under the care of a healthcare expert. However, it may not be a sustainable approach to weight loss as depriving your body of food could be harmful to your health. Let us understand in detail what is water fasting along with its benefits and risks.

What is Water Fasting?

Water fasting is associated with the complete absence of food when the body is in an environment of complete rest. It has to be followed under medical supervision and can last anywhere from 5 to 40 days. Healthcare experts advise keeping the body in a complete rest environment, as your body won't require many calories.

Additionally, some studies suggest people drink mineral water during the fasting period so that the body can absorb some essential minerals. Being one of the popular weight loss or detox techniques, this fasting could be followed for religious or spiritual reasons and to prepare a patient for a medical procedure.

Several studies have connected water fasting with some potential health benefits such as lowering the risk of diabetes, heart disease or certain cancers. This fasting may also promote a process called autophagy in which the body breaks down and recycles the potentially dangerous parts of the cells. The lemon detox cleanse is also modelled after the water fast which permits you to drink a mixture of lemon juice, maple syrup and cayenne pepper per day for up to 7 days.

How to Do Water Fasting?

There may not be scientific guidelines on how to start water fasting but, ideally, you may prepare your body for being without food for three to four days before you begin with a water fast. This could be done by eating smaller portions or by fasting for part of the day. During the water fast, most people drink two to three litres of water per day and the fast should not last beyond 72 hours. Some people may feel dizzy or weak during a fast. You can keep your body at rest during the water fast and avoid activities that may require burning more calories.

After the water fast, you must resist the urge of eating a big meal. You can begin with a smoothie or smaller meals and then proceed to larger meals as you feel more comfortable. The post-fast phase is very crucial after longer fasts as your body may be at risk of refeeding syndrome. In this condition, the body undergoes rapid changes in fluid and electrolyte levels which may cause uncomfortable medical conditions. Generally, this phase lasts a day but in certain cases, where people fast for three or more days, the body may need up to three days.

People with certain medical conditions like chronic kidney disease, diabetes, eating disorders, heartburn and gastroesophageal reflux disorder (GERD) should never try water fast without medical advice. Furthermore, pregnant or breastfeeding women, teenagers under the age of 18 and people who are overcoming an addiction or are on prescription or over-the-counter (OTC) medications should always seek the personalized advice of their healthcare provider before water fasting.

Potential Benefits of Water Fasting

Water fasting may have certain short-term health benefits but research lacks substantial evidence on the same. Some of the potential health benefits of water fasting are as follows −

May Lower Blood Pressure

Medically supervised water fasts may help lower systolic blood pressure. Drinking more water and consuming less sodium can help in managing blood pressure. Also, in water fast, you are not allowed to consume any other beverage like tea, coffee or alcohol and avoiding alcohol may help in lowering blood pressure.

May Lower the Risk of Chronic Diseases

Water fasting may significantly lower blood pressure and triglycerides. Thus, this may reduce the risk of several chronic diseases like diabetes, cancer and heart disease. Free radicals in our body can damage parts of cells and trigger chronic diseases. Water fasting may help in cell recycling and prevents the cells from accumulating and growing. However, there are very few studies on water fasting which could confirm its role in autophagy or cell recycling.

May Promote insulin and Leptin Sensitivity

Insulin sensitive body can efficiently reduce blood sugar levels, while leptin sensitive body can prominently process hunger signals and helps the body feel full. These hormones can affect the body's metabolism and lower the risk of diabetes and obesity respectively. Studies have shown that water fasting may make the body more sensitive to insulin and leptin and greater sensitivity makes them more effective in the body.

Although research may claim the potential benefit of water fasting in the reduction of oxidative stress, lowering chronic medical conditions and weight loss, it’s still unclear if the effects are long-lasting.

Risks of Water Fasting

Water fasting may not be suitable for everyone and the potential risks involved with it are as follows −

The wrong type of Weight Loss

Fasting may trigger muscle loss in the body and this could negatively lead to weight loss. Consuming just water may cause more muscle loss than fat loss.


If you are drinking water but not consuming food you may suffer from dehydration as the body doesn't get the 20 to 30 per cent daily water that comes from the foods you eat. You may experience symptoms of dehydration such as dizziness, headache, constipation, nausea and low blood pressure.

Calorie Restriction and Nutrients Deficiency

Your body cannot perform at an optimal level when you don't consume the required number of calories as per your body’s needs. Such calorie restriction may cause fatigue, brain fog and dizziness. Furthermore, restricting calories limit the intake of essential vitamins, minerals, fatty acids, electrolytes and amino acids which can put you at risk of nutrient deficiencies.


This is water intoxication which may occur when the water and salt lost through sweating are replaced by water. Hence, people are advised not to exercise during a water fast. This health condition may also make you physically inactive.

Unsafe changes in Blood Pressure

Hypotension may occur if you drink too much water and there is a sudden drop in blood pressure. This sudden drop happens when you suddenly stand up and is called orthostatic hypotension. The symptoms of hypotension like dizziness and the risk of fainting could lead to an accident.

In addition to the above-mentioned risks, water fasting can often lead to digestive upset and binge eating and increase the risk of medical conditions like refeeding syndrome and gout.


Even though water fasting may have potential benefits; it does not adhere to the 2020-2025 United States Department of Agriculture (USDA) dietary guidelines. As a short-term diet, water fasting may be helpful, but the risks associated with this diet are more than the benefits. It is thus advised to go for water fasting only under medical supervision.

Updated on: 09-Feb-2023


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