The 2 Day Water Fast: A Complete Guide [How To + What To Expect]

Our nutrition coach discusses the risks and benefits of water fasting for 2 days.

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Although intermittent fasting diets seem to be a recent health trend and weight loss strategy, fasting has been practiced for thousands of years. 

The most common intermittent fasting diets involve time-restricted eating patterns, such as 18/6 intermittent fasting, wherein each day includes an 18-hour fast and a six-hour eating window, or a stricter intermittent fasting 20/4.

But, there are also intermittent fasting diets that use an alternate day protocol, by fasting 24 hours every other day and eating regularly on the off days.

This type of approach to eating, health, and weight management can be extended to longer fasts such as a 2 day water fast.

A water-only fast for 48 hours can potentially be a strategy to help burn fat, reach a healthy weight, and experience some of the other benefits of water fasting such as improving the regulation of blood sugar levels. However, there are also risks of extended fasting.

In this guide to 2 day water fasting, we will discuss how to do a 2 day water fast, tips for getting through the fasting period, and how to prepare for water fasting for 2 days.

A glass of water and an alarm clock.

What Is a 2 Day Water Fast?

Before we look at the potential health benefits of water fasting and how to do water-only fasting, it’s important to present the disclaimer that I am a certified nutrition coach with a master’s degree in Exercise Science and Nutrition.

However, I am not a registered dietitian (RDN) nor a healthcare professional, so this should not be taken as medical advice.

Water fasting is not safe for certain individuals, especially those with underlying medical conditions or chronic diseases, women who are pregnant or breastfeeding, individuals with a history of eating disorders, or those who have health conditions that affect blood sugar regulation (such as anyone with type 1 or type 2 diabetes or insulin resistance).

A water fast1Finnell, J. S., Saul, B. C., Goldhamer, A. C., & Myers, T. R. (2018). Is fasting safe? A chart review of adverse events during medically supervised, water-only fasting. BMC Complementary and Alternative Medicine18(1). https://doi.org/10.1186/s12906-018-2136-6 involves abstaining from all food and caloric beverages and only drinking water for the duration of the fast.

Intermittent fasting is a short-term version of water fasting that might involve extending your overnight fast through the next afternoon and eating your first meal mid-day.

Some people do 24-hour water fasts or even 36-hour water fasts as an ongoing diet plan to help support weight loss rather than restricting calories to a moderate amount every day.

A 2 day water fast is an even more extreme protocol of water fasting, requiring the complete abstinence of all food and caloric beverages for a full 48 hours. 

A 48 hour water fast is often performed by people who want to lose weight, improve overall health and wellness, and know that something like a 5-day water fasting is an unsafe period of time to abstain from nutrients.

Three empty plates with the word fasting written above them.

Is a 48 Hour Water Fast Safe?

Any type of fasting can potentially help lower your body weight to reduce the risk of obesity and may improve other markers of health.2Johnson, J. B., Summer, W., Cutler, R. G., Martin, B., Hyun, D.-H., Dixit, V. D., Pearson, M., Nassar, M., Tellejohan, R., Maudsley, S., Carlson, O., John, S., Laub, D. R., & Mattson, M. P. (2007). Alternate day calorie restriction improves clinical findings and reduces markers of oxidative stress and inflammation in overweight adults with moderate asthma. Free Radical Biology and Medicine42(5), 665–674. https://doi.org/10.1016/j.freeradbiomed.2006.12.005

‌However, most medical providers say that it is unnecessary to do prolonged fasting to achieve the effect of fasting on your metabolism, hormones, and insulin sensitivity.

With that said, 2 day water fasting teeters right on the edge of what most people can safely attempt on their own to maximize the benefits of fasting and an overly aggressive and potentially unsafe fasting routine that requires medical guidance and supervision.

However, it is still highly recommended that you speak with a healthcare professional to discuss the potential risks, side effects, and important safety considerations before doing a 48 hour water fast.

Medical supervision3Wilhelmi de Toledo, F., Buchinger, A., Burggrabe, H., Hölz, G., Kuhn, C., Lischka, E., Lischka, N., Lützner, H., May, W., Ritzmann-Widderich, M., Stange, R., Wessel, A., Boschmann, M., Peper, E., & Michalsen, A. (2013). Fasting Therapy – an Expert Panel Update of the 2002 Consensus Guidelines. Forschende Komplementärmedizin / Research in Complementary Medicine20(6), 434–443. https://doi.org/10.1159/000357602 will help ensure that water fasting for 2 days does not put your health in danger, and your doctor may have specific concerns or recommendations for safer diet and weight loss practices.

Long-term fasting4Ogłodek, E., & Pilis, Prof., W. (2021). Is Water-Only Fasting Safe? Global Advances in Health and Medicine10, 216495612110311. https://doi.org/10.1177/21649561211031178 can result in dangerous electrolyte and blood sugar imbalances, low blood pressure, poor hydration levels, loss of muscle mass, high uric acid levels, and deficiencies that can potentially affect your cognition, decision-making ability, focus, nerve conduction, fluid balance, muscle contraction, and even heart rate and rhythm.

Pouring a glass of water.

How to Prepare for a 2 Day Water Fast

When people first take an interest in 2-day water fasting, they often ask, “Can I water fast for 2 days?”

This question can actually entail two underlying sub-questions: How do you do a 48-hour water fast from a physical or practical standpoint (what can you eat, what supplements do you need, etc.), and can I water fast for 2 days from a mental standpoint (will I be able to control my appetite, cravings, hunger, etc.)?

Both aspects are important for success during your 2 day water fast, so it’s helpful to begin physically and mentally preparing yourself before the actual water fast begins.

To physically prepare for a 48 hour water fast, it’s often helpful to try shorter water fasting protocols, such as time-restricted intermittent fasting with reduced eating windows.

For example, you might try 20/4 intermittent fasting for a week or two leading up to your 2 day water fast. This is a time-restricted eating approach that involves prolonging the overnight fast for a full 20 hours every day and then only eating during a four-hour window.

Or, you might try doing a 24 hour water fast the week before your 48-hour water fast.

These “mini“ fasts can help your body rehearse some of the physical sensations that you will experience during a 2 day water fast so that it won’t be a complete shock to the system once you cease all energy intake for a full two days.

An empty place setting symbolizing the 2 day water fast.

Even if you decide that you do not want to try any sort of shorter fasting protocols to practice for your full 2 day water fasting diet, it is still a good idea to be deliberate in your food choices in the several days leading up to your water fast. 

Focus on eating nourishing, easily digestible foods such as fresh vegetables and fruits, lean proteins, eggs, soups, and fermented foods. 

Avoid alcohol, excessive caffeine, and processed foods high in sugar, salt, and industrial oils. It is also usually helpful to avoid particularly fatty meats and rich, heavy foods, as these can slow digestion and ultimately are probably not supportive of the health and weight loss goals you are striving for by taking on a 48 hour water fast in the first place.

Mentally preparing for a 2 day water fast is highly individualized and depends on your experience with fasting, your comfort level being hungry, whether you often feel cravings for carbs or other foods (and how difficult it is for you to resist!), and methods that work well for you to help you through difficult situations— your best “self-care tool kit,“ if you will.

It is a good idea to preemptively brainstorm a few strategies that tend to help you through uncomfortable physical and emotional sensations and be prepared to rely on them when things get tough.

Examples include journaling, mindfulness meditation, walking, arts and crafts, Reiki, prayer, singing, or relaxing by watching your favorite TV shows.

Ultimately there’s no way around it: fasting for 48 hours is likely going to be physically and emotionally difficult, and you will experience hunger pangs, dips in energy, and moods that you might not be accustomed to.

However, if you are motivated by the potential benefit of a 2 day water fast, these discomforts might be worth it and are all part of the journey; furthermore, it is partially the very challenge of overcoming the discomfort that drives many people to do prolonged fasting.

The one thing to be mindful of is that if you start to experience adverse symptoms or concerning physical sensations, it is important to let go of your ego and your motivational drive to accomplish what you have set out to achieve and seek medical support or resume eating as soon as possible.

What Are the Benefits of Fasting for 2 Days?

When we fast, the body has to become metabolically flexible in the sense that we have to start burning alternative fuels for energy. 

When you are taking in calories from a well-rounded diet on a consistent basis to meet your energy needs, your body can readily use carbohydrates and fats to create energy and maintain proper blood glucose levels. 

Certain cells in the body, such as the brain cells and the cells in the medulla of the kidneys, require glucose (sugar) to survive and cannot use alternative sources of energy. 

This glucose can be easily obtained by breaking down dietary carbohydrates or stored glycogen in your muscles and liver.

However, if you are on the keto diet, another low-carbohydrate diet, or are fasting, your glycogen stores will become depleted, leaving no ready access to glucose. 

In these situations, the liver can create glucose, in a process termed gluconeogenesis, through other substrates. However, this process is energy intensive. 

Practicing shorter fasting protocols can help your body become more efficient at gluconeogenesis, as well as burning ketones for energy, which is the other metabolic “consequence“ of prolonged fasting. 

Ketosis is associated with many physical benefits, but it can be a shock to the body if you are suddenly having to function largely on ketones for energy when you are accustomed to carbohydrates.

Intermittent fasting is written on a clipboard, an empty plate, a clock, and utensils.

Health benefits of water fasting can include fat loss,5Tinsley, G. M., & La Bounty, P. M. (2015). Effects of intermittent fasting on body composition and clinical health markers in humans. Nutrition Reviews73(10), 661–674. https://doi.org/10.1093/nutrit/nuv041 reducing oxidative stress and chronic inflammation,6Johnson, J. B., Summer, W., Cutler, R. G., Martin, B., Hyun, D.-H., Dixit, V. D., Pearson, M., Nassar, M., Tellejohan, R., Maudsley, S., Carlson, O., John, S., Laub, D. R., & Mattson, M. P. (2007). Alternate day calorie restriction improves clinical findings and reduces markers of oxidative stress and inflammation in overweight adults with moderate asthma. Free Radical Biology and Medicine42(5), 665–674. https://doi.org/10.1016/j.freeradbiomed.2006.12.005 decreasing LDL (“bad”) cholesterol and triglycerides levels,7Bhutani, S., Klempel, M. C., Berger, R. A., & Varady, K. A. (2010). Improvements in Coronary Heart Disease Risk Indicators by Alternate-Day Fasting Involve Adipose Tissue Modulations. Obesity18(11), 2152–2159. https://doi.org/10.1038/oby.2010.54 promoting autophagy (cell cleanup) and cellular health,8Bagherniya, M., Butler, A. E., Barreto, G. E., & Sahebkar, A. (2018). The effect of fasting or calorie restriction on autophagy induction: A review of the literature. Ageing Research Reviews47, 183–197. https://doi.org/10.1016/j.arr.2018.08.004 reducing the risk of hypertension (high blood pressure), boosting the secretion of human growth hormone (HGH), improving blood sugar regulation,9Barnosky, A. R., Hoddy, K. K., Unterman, T. G., & Varady, K. A. (2014). Intermittent fasting vs daily calorie restriction for type 2 diabetes prevention: a review of human findings. Translational Research164(4), 302–311. https://doi.org/10.1016/j.trsl.2014.05.013 and reducing the risk of diseases including cancer, heart disease and heart failure, and neurodegenerative diseases.

Electrolyte powder being poured into a glass.

How to Do a 2 Day Water Fast

Once the 2 day water fast begins, all you have to do is drink plain water, or water with unsweetened electrolyte powders that contain sodium, potassium, magnesium, and calcium, for a full 48 hours.

Aim to drink a minimum of 1-2 liters of water per day, and more if you have a larger body, sweat a lot, or live in a hot climate.

Electrolyte tablets will help prevent electrolyte imbalances, or hyponatremia,10Ogłodek, E., & Pilis, Prof., W. (2021). Is Water-Only Fasting Safe? Global Advances in Health and Medicine10, 216495612110311. https://doi.org/10.1177/21649561211031178 a potentially fatal condition in which sodium concentration in your body becomes too depleted.

Make sure to slowly reintroduce foods after extended fasting to reduce the risk of refeeding syndrome.11Mehanna, H. M., Moledina, J., & Travis, J. (2008). Refeeding syndrome: what it is, and how to prevent and treat it. BMJ336(7659), 1495–1498. https://doi.org/10.1136/bmj.a301

Refeeding syndrome is a dangerous condition that can occur if you eat too much too soon after prolonged fasting. 

A 48 hour water fast is a challenging but potentially doable approach to boosting health and reducing body fat. However, it is advisable to speak with your healthcare team before embarking on a 2 day water fast to make sure it’s the best choice for you.

To start out with a 24-hour water fast first, check out our guide to 24-hour water fasting here.

A clock with utensils as hands.

References

  • 1
    Finnell, J. S., Saul, B. C., Goldhamer, A. C., & Myers, T. R. (2018). Is fasting safe? A chart review of adverse events during medically supervised, water-only fasting. BMC Complementary and Alternative Medicine18(1). https://doi.org/10.1186/s12906-018-2136-6
  • 2
    Johnson, J. B., Summer, W., Cutler, R. G., Martin, B., Hyun, D.-H., Dixit, V. D., Pearson, M., Nassar, M., Tellejohan, R., Maudsley, S., Carlson, O., John, S., Laub, D. R., & Mattson, M. P. (2007). Alternate day calorie restriction improves clinical findings and reduces markers of oxidative stress and inflammation in overweight adults with moderate asthma. Free Radical Biology and Medicine42(5), 665–674. https://doi.org/10.1016/j.freeradbiomed.2006.12.005
  • 3
    Wilhelmi de Toledo, F., Buchinger, A., Burggrabe, H., Hölz, G., Kuhn, C., Lischka, E., Lischka, N., Lützner, H., May, W., Ritzmann-Widderich, M., Stange, R., Wessel, A., Boschmann, M., Peper, E., & Michalsen, A. (2013). Fasting Therapy – an Expert Panel Update of the 2002 Consensus Guidelines. Forschende Komplementärmedizin / Research in Complementary Medicine20(6), 434–443. https://doi.org/10.1159/000357602
  • 4
    Ogłodek, E., & Pilis, Prof., W. (2021). Is Water-Only Fasting Safe? Global Advances in Health and Medicine10, 216495612110311. https://doi.org/10.1177/21649561211031178
  • 5
    Tinsley, G. M., & La Bounty, P. M. (2015). Effects of intermittent fasting on body composition and clinical health markers in humans. Nutrition Reviews73(10), 661–674. https://doi.org/10.1093/nutrit/nuv041
  • 6
    Johnson, J. B., Summer, W., Cutler, R. G., Martin, B., Hyun, D.-H., Dixit, V. D., Pearson, M., Nassar, M., Tellejohan, R., Maudsley, S., Carlson, O., John, S., Laub, D. R., & Mattson, M. P. (2007). Alternate day calorie restriction improves clinical findings and reduces markers of oxidative stress and inflammation in overweight adults with moderate asthma. Free Radical Biology and Medicine42(5), 665–674. https://doi.org/10.1016/j.freeradbiomed.2006.12.005
  • 7
    Bhutani, S., Klempel, M. C., Berger, R. A., & Varady, K. A. (2010). Improvements in Coronary Heart Disease Risk Indicators by Alternate-Day Fasting Involve Adipose Tissue Modulations. Obesity18(11), 2152–2159. https://doi.org/10.1038/oby.2010.54
  • 8
    Bagherniya, M., Butler, A. E., Barreto, G. E., & Sahebkar, A. (2018). The effect of fasting or calorie restriction on autophagy induction: A review of the literature. Ageing Research Reviews47, 183–197. https://doi.org/10.1016/j.arr.2018.08.004
  • 9
    Barnosky, A. R., Hoddy, K. K., Unterman, T. G., & Varady, K. A. (2014). Intermittent fasting vs daily calorie restriction for type 2 diabetes prevention: a review of human findings. Translational Research164(4), 302–311. https://doi.org/10.1016/j.trsl.2014.05.013
  • 10
    Ogłodek, E., & Pilis, Prof., W. (2021). Is Water-Only Fasting Safe? Global Advances in Health and Medicine10, 216495612110311. https://doi.org/10.1177/21649561211031178
  • 11
    Mehanna, H. M., Moledina, J., & Travis, J. (2008). Refeeding syndrome: what it is, and how to prevent and treat it. BMJ336(7659), 1495–1498. https://doi.org/10.1136/bmj.a301
Photo of author
Amber Sayer is a Fitness, Nutrition, and Wellness Writer and Editor, as well as a NASM-Certified Nutrition Coach and UESCA-certified running, endurance nutrition, and triathlon coach. She holds two Masters Degrees—one in Exercise Science and one in Prosthetics and Orthotics. As a Certified Personal Trainer and running coach for 12 years, Amber enjoys staying active and helping others do so as well. In her free time, she likes running, cycling, cooking, and tackling any type of puzzle.

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