Fasting is an ancient practice where people abstain from food (and sometimes drink) for a limited period of time [1]. It’s been part of many cultures for centuries. The reasons behind this practice were mostly of spiritual and religious nature, but people have been practicing it for medical reasons as well.

Water fasting, specifically, is a type of fast where you consume only water and nothing else for a set period. Nowadays, interest in water fasting seems to be growing, mostly as a way to lose weight. But is water fasting a good weight-loss and health-boosting method? To answer that, here’s an overview of what water fasting actually is and how it may or may not work.

What Exactly Is Water Fasting?

Water fasting, also known as water-only fasting, is a type of fast. It’s similar to other fasting methods like intermittent fasting, the 5:2 diet, and alternate-day fasting in some respects. What makes it different from some other fasting methods is that you’re allowed to consume only water during the whole duration of the fast.

Water fasting usually lasts 24–72 hours because anything longer than that can be dangerous, especially without medical supervision. A study examining the safety of a water-only fast found that fasting for 2 consecutive days under medical supervision was generally safe [2]. Adverse events in this study included fatigue, nausea, insomnia, headache, hypertension, and lightheadedness, to name a few.

The history of water fasting can be traced back to ancient religious practices, like days of Paryushan in Jainism or the eucharistic fast of Roman Catholicism.

Today, many people follow water-only fasts to lose weight or to detox.

Water Fasting Benefits

Other than for religious and spiritual reasons, many people water fast to reap its health benefits. Here are some of the potential health benefits of water fasting.

May reduce oxidative stress

In one study, 10 participants completed water fast for 11 days and then followed a regeneration diet for 11 days. Results revealed that water fasting reduced oxidative stress, body weight, and blood pressure [3].

May improve insulin sensitivity

Insulin resistance is when your body’s cells don’t respond correctly to the signals from the insulin hormone. This can lead to a spike in blood sugar and also cause other adverse effects such as weight gain. Fasting has been found to improve insulin resistance and decrease blood sugar levels.

One study investigated the effectiveness of fasting in 10 adults with type 2 diabetes [4]. Results showed that fasting helped improve blood sugar and body weight without any adverse effects.

May normalize blood pressure

A 2001 study explored the effectiveness of water fasting in 170 patients with high blood pressure [5]. The patients were put on a short pre-fasting period for 2–3 days in which they only consumed fruits and vegetables. After that, they completed a medically supervised water fasting for 11 days, followed by a week of refeeding. Results revealed that medically supervised water fasting was safe and effective in normalizing blood pressure.

Water Fasting Risks

Water fasting, especially prolonged water fasting (more than 72 hours) can cause adverse effects in some people. Some of those side effects are [2]:

  • Symptoms related to loss of electrolytes
  • Fatigue
  • Dizziness
  • Vomiting
  • Headache

How to Water Fast

Before you try your hands at water wasting, it’s a good idea to learn more about the dangers and risks associated with water fasting. Dehydration, electrolyte imbalances, hypoglycemia, and other problems are real risks associated with water fasting, especially if you find that any of the following applies to you:

  • Diabetes
  • Kidney disease
  • Pregnant and/or breastfeeding
  • Eating disorders

With that said, here are steps you need to take to safely practice water fasting for weight loss or better overall health.

1. Warm-up

If you’ve never fasted before, it might be a good idea to prepare for your water fast for a few days first. You could start by reducing the portion size of your meals, or you could try replacing a meal with water. Do this for 4–5 days to prepare your body and to see how your body may react when you start the water fast.

2. Stick with 24–72 hours only

You may come across testimonies of people claiming they did the water fast without any adverse effects for 20+ days. However, it can be dangerous to try that. The safe recommended time to water fast is anywhere between 24–72 hours.

3. Try it during the weekend or days off

Water fasting is not for everyone, and it may cause weakness and dizziness in some people. If your job requires a lot of physical and mental effort, you may want to try the water fast during the weekend or on your days off.

4. Resist the urge to eat a big meal after your fast.

You may be starving by the end of your fast and feel the urge to consume a large meal. However, you should resist the urge to do that because it may cause some adverse effects such as bloating and other digestive problems. Instead, break your fast with a light meal or a smoothie, and you can gradually increase the portion size throughout the day.


  1. Water fasting is a type of fast that requires you to consume only water during the whole duration of the fast.
  2. Typical water and most recommended water fast is anywhere between 24–72 hours, and anything more than that can cause severe consequences in some people.
  3. Please consult with your doctor before trying a water fast, especially if you have health conditions such as diabetes or low blood sugar.


  1. Fasting. Encyclopaedia Britannica. 2020 Jan. —
  2. Finnell JS, Saul BC, Goldhamer AC, R. Myers T. Is fasting safe? A chart review of adverse events during medically supervised, water-only fasting. BMC Complement Altern Med. 2018; 18: 67. –
  3. Mojto V, Gvozdjakova A, Kucharska J, Rausova Z, Vancova O, Valuch J. Effects of complete water fasting and regeneration diet on kidney function, oxidative stress and antioxidants. Bratisl Lek Listy. 2018;119(2):107–111.
  4. Arnason TG, Bowen MW, Mansell KD. Effects of intermittent fasting on health markers in those with type 2 diabetes: A pilot study. World J Diabetes. 2017 Apr 15; 8(4): 154–164.
  5. Goldhamer A, Lisle D, Parpia B, Anderson SV, Campbell TC. Medically supervised water-only fasting in the treatment of hypertension. J Manipulative Physiol Ther. 2001 Jun;24(5):335–


Cited from MEDIUM.COM