How To Do A 5 Day Fast: The Complete Guide

Plus, the potential benefits and risks.

Fasting has been practiced for thousands of years in one way or another, and there are still many popular fasting diets and protocols that people use today.

For example, there are quite a number of iterations of intermittent fasting diets.

Some intermittent fasting diets involve time-restricted eating patterns, such as 20/4 intermittent fasting, wherein each day includes a 20-hour fast and a four-hour eating window, or intermittent fasting 18/6.

Then, there are intermittent fasting diets that use an alternate-day protocol, while other people practice fasting by doing a 24-hour fast once a week or 36-hour fast once a week. 

When you want to do “advanced” fasting, you might even try a 5 day water fast. 

In this guide, we will discuss the need-to-know details about how to prepare for and do a 5 day fast and if it’s a safe and beneficial practice that you should include in your health regimen.

Pour a glass of water for a 5 day water fast.

What Is a 5 Day Fast?

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 fasting from all food and caloric beverages and only allowing the consumption of water. 

Some people do 24-hour or 36-hour water fasts, which essentially involve abstaining from all caloric food and beverages for one day or one and half days, respectively, as a form of intermittent fasting. 

For example, someone may do a 24-hour fast once a week as an ongoing diet plan to help support weight loss rather than doing a daily calorie restriction diet.

A 5 day fast is an even more extreme protocol of water fasting, requiring the complete abstinence of all food and caloric beverages for a full five days.

It is often performed by people who want to work up to water fasting for a week.

Although such a prolonged water fast can support weight loss and may improve other markers of health, most medical providers would give the disclaimer that water fasting for a week is an extreme practice that is unsuitable and potentially dangerous for most individuals.

Therefore, if you are interested in embarking on a 5 day fast, it is highly recommended that you speak with your healthcare team to discuss the potential risk factors and important safety considerations.

Two doctors.

Is 5 Day Fasting Safe?

Long-term fasting2Ogłodek, 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 various side effects such as dangerous electrolyte and sugar imbalances or deficiencies that can potentially affect your cognition, decision-making ability, focus, nerve conduction, fluid balance, muscle contraction, and even heart rate and rhythm.

It’s very important to speak with your doctor before trying prolonged fasting.

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 5 day water fasting does not harm your health, and your doctor may have specific concerns or recommendations for safer fasting practices.

What Are The Potential Health Benefits Of a 5-Day Fast?

Research shows the potential benefits of fasting for certain medical conditions and health conditions.

  • Reducing the risk of cardiovascular disease and coronary artery disease 
  • Reducing the risk of metabolic syndrome by decreasing triglycerides.4Horne, B. D., Muhlestein, J. B., Lappé, D. L., May, H. T., Carlquist, J. F., Galenko, O., Brunisholz, K. D., & Anderson, J. L. (2013). Randomized cross-over trial of short-term water-only fasting: Metabolic and cardiovascular consequences. Nutrition, Metabolism and Cardiovascular Diseases23(11), 1050–1057. https://doi.org/10.1016/j.numecd.2012.09.007
  • Helping your body fight cancer.5Di Biase, S., Lee, C., Brandhorst, S., Manes, B., Buono, R., Cheng, C.-W., Cacciottolo, M., Martin-Montalvo, A., de Cabo, R., Wei, M., Morgan, T. E., & Longo, V. D. (2016). Fasting-Mimicking Diet Reduces HO-1 to Promote T Cell-Mediated Tumor Cytotoxicity. Cancer Cell30(1), 136–146. https://doi.org/10.1016/j.ccell.2016.06.005
  • Reducing the risk of heart attack and stroke.6MATTSON, M., & WAN, R. (2005). Beneficial effects of intermittent fasting and caloric restriction on the cardiovascular and cerebrovascular systems. The Journal of Nutritional Biochemistry16(3), 129–137. https://doi.org/10.1016/j.jnutbio.2004.12.007
  • Increasing the production of human growth hormone (HGH).7Home Page: The American Journal of Clinical Nutrition. (n.d.). Ajcn.nutrition.org. https://ajcn.nutrition.org/
  • Promoting optimal cellular health and autophagy, which is a cellular clean-up process whereby the healthy cells get rid of cellular waste products and dead and damaged cells.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
  • Helping the body defend your body from oxidative stress, which is damage that occurs from free radicals and reactive species.9Cienfuegos, S., Gabel, K., Kalam, F., Ezpeleta, M., Wiseman, E., Pavlou, V., Lin, S., Oliveira, M. L., & Varady, K. A. (2020). Effects of 4- and 6-h Time-Restricted Feeding on Weight and Cardiometabolic Health: A Randomized Controlled Trial in Adults with Obesity. Cell Metabolism32(3), 366-378.e3. https://doi.org/10.1016/j.cmet.2020.06.018
  • Reducing inflammation, a key driver underlying many chronic diseases such as obesity, metabolic syndrome, type 2 diabetes, heart disease, and certain cancers.10Jordan, S., Tung, N., Casanova-Acebes, M., Chang, C., Cantoni, C., Zhang, D., Wirtz, T. H., Naik, S., Rose, S. A., Brocker, C. N., Gainullina, A., Hornburg, D., Horng, S., Maier, B. B., Cravedi, P., LeRoith, D., Gonzalez, F. J., Meissner, F., Ochando, J., & Rahman, A. (2019). Dietary Intake Regulates the Circulating Inflammatory Monocyte Pool. Cell178(5), 1102-1114.e17. https://doi.org/10.1016/j.cell.2019.07.050
  • Stimulating neurogenesis (the growth of new neurons).11Baik, S.-H., Rajeev, V., Fann, D. Y.-W., Jo, D.-G., & Arumugam, T. V. (2020). Intermittent fasting increases adult hippocampal neurogenesis. Brain and Behavior10(1), e01444. https://doi.org/10.1002/brb3.1444
  • Increasing longevity.12Goodrick, C. L., Ingram, D. K., Reynolds, M. A., Freeman, J. R., & Cider, N. L. (1982). Effects of intermittent feeding upon growth and life span in rats. Gerontology28(4), 233–241. https://doi.org/10.1159/000212538
  • Reducing insulin levels, which can reduce the risk of insulin resistance while also supporting body fat loss.13Hoddy, K. K., Gibbons, C., Kroeger, C. M., Trepanowski, J. F., Barnosky, A., Bhutani, S., Gabel, K., Finlayson, G., & Varady, K. A. (2016). Changes in hunger and fullness in relation to gut peptides before and after 8 weeks of alternate day fasting. Clinical Nutrition35(6), 1380–1385. https://doi.org/10.1016/j.clnu.2016.03.011
  • Increasing metabolic rate assisting in maintaining or obtaining a healthy body weight or lowering BMI.14Teruya, T., Chaleckis, R., Takada, J., Yanagida, M., & Kondoh, H. (2019). Diverse metabolic reactions activated during 58-hr fasting are revealed by non-targeted metabolomic analysis of human blood. Scientific Reports9(1). https://doi.org/10.1038/s41598-018-36674-9
  • Reducing the risk of various diseases, such as diabetes, certain cancers, and neurodegenerative diseases.
  • Putting the body in a state of ketosis. Ketosis is a metabolic state where the body burns stored fat instead of glucose for fuel.

How to Prepare for a 5 Day Water Fast

As mentioned, before you actually start your 5 day fast, you should speak with your doctor to obtain medical clearance and discuss alternatives. 

If you get the go-ahead, you should begin physically and mentally preparing —both aspects are important.

To physically prepare for a 5 day fast, it’s typically helpful to try shorter water fasting protocols, such as 24-hour fasting or intermittent fasting, with reducing your eating windows.

For example, you might try 20/4 intermittent fasting for a week or two leading up to your 5 day water fast. This time-restricted eating approach involves prolonging the overnight fast for a full 20 hours every day and then only consuming food during a four-hour window.

No matter how you structure your “mini“ fasts, rehearsing some of the physical sensations you will experience during a 5 day fast will help prevent your body from feeling totally shocked by a sudden cessation of energy intake for numerous days in a row.

Even if you decide that you want to jump right into the 5 day water fasting without trying a shorter fast, you should prepare your body by carefully controlling your diet in the days leading up to your fast. 

Avoid highly-processed foods, such as refined grains, sweets and pastries, soda, alcohol, processed meats, hydrogenated oils and trans fats, and fatty meats.

These foods can irritate the gut microbiome and are very difficult to digest.

Furthermore, if you are fasting for weight loss or body fat loss, processed foods will work against your efforts because they are calorically dense but not nutritionally dense.

It’s also a good idea to prepare yourself mentally because 5 day water fasting is going to test your willpower, determination, and mindfulness. 

Make sure that you have gathered a few ideas for how you will deal with difficult emotions and challenging moments during your fast, such as meditation, journaling, and yoga workouts.

Pouring a glass of water.

How to Do a 5 Day Fast

So, how do you do a 5 day water fast?

Once you feel that you are ready, begin your 5 day water fast by abstaining from all food and caloric beverages for a full five days. 

Some people choose to also have non-caloric beverages like green tea, herbal tea, club soda, or very low-calorie beverages such as black coffee during the fast.

It’s also advisable to supplement your water with noncaloric, unsweetened electrolyte powders or have electrolyte tablets or capsules.

However, according to some water fasting gurus, during strict 5 day water fasting protocols, you are only technically allowed to lick pure pink Himalayan salt.

Of course, if you experience any concerning symptoms as you are fasting, you should consult your doctor immediately.

Pink Himalayan salt.

What Should You Eat After a 5 Day Water Fast?

When you fast, the digestive system gets a break15Puigserver, A., Wicker, C., & Gaucher, C. (1985). [Molecular aspects of the adaptation of pancreatic and intestinal enzymes to dietary regimens]. Reproduction, Nutrition, Developpement25(4B), 787–801. https://pubmed.ncbi.nlm.nih.gov/2417292/ from needing to process, digest, and absorb all the different foods and drinks you normally consume.

While this can be beneficial, and there are quite a number of potential benefits of fasting in general, jumping right back into your normal diet after a period of prolonged fasting (longer than the regular overnight fast) can be an unwelcome shock to your gut, especially if you were fasting for upwards of 24 hours or more.

Going from having nothing in your digestive tract—and thus allowing your digestive system to have a mini “vacation“ of sorts— to suddenly having a rich, heavy, calorie-laden meal can be a recipe for not only undoing some of the potential weight loss and health benefits of your fast, but also for a very uncomfortable and unhappy digestive system.

Furthermore, there is a condition called refeeding syndrome16Mehanna, 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 that can occur if you eat too much too soon after prolonged fasting. 

This dangerous condition is a result of the rapid changes in electrolytes and water balance that can occur once you finally give your body some nutrients after a prolonged fast.

Certain electrolytes, such as potassium, magnesium, and phosphate, are required for digesting and absorbing nutrients such as carbs, but because these electrolytes are depleted during extended water fasts, your body‘s ability to properly digest carbohydrates becomes significantly impaired.

Therefore, you need to gradually ease back into eating and choose foods to break your fast that are lower in carbohydrates, rich in electrolytes, and gentle on the stomach. 

Avoid processed foods and fatty foods like meat, fried food, and sweets, along with alcohol and some dairy products like cheese, ice cream, and full-fat milk.

After fasting for nearly a week, it is also best to avoid food such as raw cruciferous vegetables, legumes, seeds and seed bladders, and nuts and nut butter.

Although these are typically considered healthy foods and should be incorporated as part of your everyday diet, they can be difficult to digest.

It is not uncommon to experience excessive gas or sharp gas pains17Perez, F., Accarino, A., Azpiroz, F., Quiroga, S., & Malagelada, Juan-R. (2007). Gas distribution within the human gut: effect of meals. The American Journal of Gastroenterology102(4), 842–849. https://doi.org/10.1111/j.1572-0241.2007.01071.x when trying to digest high-fiber after a period of fasting because the digestive system is completely empty.

Therefore, ease slowly into eating beans, peas, lentils, nuts, peanut butter, flaxseeds, pumpkin seeds, squash seeds, raw broccoli, cauliflower, kale, or Brussels sprouts after fasting.

Cooked vegetables in a pan.

You can eat cauliflower, broccoli, and other cruciferous vegetables after fasting, but it’s a good idea to cook them because this helps break down some of the indigestible fibers. 

In fact, many people find that steamed cauliflower, brussels sprouts, or broccoli can be some of the best foods to eat to break a fast, but it is important to cook them thoroughly to reduce the risk of gas pains or a stomachache.

Most importantly, the worst foods to eat after fasting are those that you are not very accustomed to eating, particularly if they are high in sugar or fat.

For example, if you normally follow a very healthy diet filled with whole, natural, unprocessed foods like vegetables, fruits, whole grains, lean proteins, eggs, seeds, and nuts, it’s not a good idea to break your fast with toaster pastries or a couple of donuts. Try to hold off on your cravings!

Typically, fermented foods, bone broth, and cooked vegetables are a good starting place, but it’s important that you speak with your doctor to get individualized guidance about what foods to eat after fasting for 5 days.

To maximize the benefits and minimize the risks of 5 day water fasting, work with your doctor and discuss potential concerns.

Again, please remember to speak with your healthcare provider before taking on a prolonged fast, especially if you have a history of eating disorders or other preexisting medical conditions such as diabetes, where your blood sugar levels could dip dangerously low.

To warm up to a prolonged fast, check out this next guide.

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
    Ogłodek, E., & Pilis, Prof., W. (2021). Is Water-Only Fasting Safe? Global Advances in Health and Medicine10, 216495612110311. https://doi.org/10.1177/21649561211031178
  • 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
    Horne, B. D., Muhlestein, J. B., Lappé, D. L., May, H. T., Carlquist, J. F., Galenko, O., Brunisholz, K. D., & Anderson, J. L. (2013). Randomized cross-over trial of short-term water-only fasting: Metabolic and cardiovascular consequences. Nutrition, Metabolism and Cardiovascular Diseases23(11), 1050–1057. https://doi.org/10.1016/j.numecd.2012.09.007
  • 5
    Di Biase, S., Lee, C., Brandhorst, S., Manes, B., Buono, R., Cheng, C.-W., Cacciottolo, M., Martin-Montalvo, A., de Cabo, R., Wei, M., Morgan, T. E., & Longo, V. D. (2016). Fasting-Mimicking Diet Reduces HO-1 to Promote T Cell-Mediated Tumor Cytotoxicity. Cancer Cell30(1), 136–146. https://doi.org/10.1016/j.ccell.2016.06.005
  • 6
    MATTSON, M., & WAN, R. (2005). Beneficial effects of intermittent fasting and caloric restriction on the cardiovascular and cerebrovascular systems. The Journal of Nutritional Biochemistry16(3), 129–137. https://doi.org/10.1016/j.jnutbio.2004.12.007
  • 7
    Home Page: The American Journal of Clinical Nutrition. (n.d.). Ajcn.nutrition.org. https://ajcn.nutrition.org/
  • 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
    Cienfuegos, S., Gabel, K., Kalam, F., Ezpeleta, M., Wiseman, E., Pavlou, V., Lin, S., Oliveira, M. L., & Varady, K. A. (2020). Effects of 4- and 6-h Time-Restricted Feeding on Weight and Cardiometabolic Health: A Randomized Controlled Trial in Adults with Obesity. Cell Metabolism32(3), 366-378.e3. https://doi.org/10.1016/j.cmet.2020.06.018
  • 10
    Jordan, S., Tung, N., Casanova-Acebes, M., Chang, C., Cantoni, C., Zhang, D., Wirtz, T. H., Naik, S., Rose, S. A., Brocker, C. N., Gainullina, A., Hornburg, D., Horng, S., Maier, B. B., Cravedi, P., LeRoith, D., Gonzalez, F. J., Meissner, F., Ochando, J., & Rahman, A. (2019). Dietary Intake Regulates the Circulating Inflammatory Monocyte Pool. Cell178(5), 1102-1114.e17. https://doi.org/10.1016/j.cell.2019.07.050
  • 11
    Baik, S.-H., Rajeev, V., Fann, D. Y.-W., Jo, D.-G., & Arumugam, T. V. (2020). Intermittent fasting increases adult hippocampal neurogenesis. Brain and Behavior10(1), e01444. https://doi.org/10.1002/brb3.1444
  • 12
    Goodrick, C. L., Ingram, D. K., Reynolds, M. A., Freeman, J. R., & Cider, N. L. (1982). Effects of intermittent feeding upon growth and life span in rats. Gerontology28(4), 233–241. https://doi.org/10.1159/000212538
  • 13
    Hoddy, K. K., Gibbons, C., Kroeger, C. M., Trepanowski, J. F., Barnosky, A., Bhutani, S., Gabel, K., Finlayson, G., & Varady, K. A. (2016). Changes in hunger and fullness in relation to gut peptides before and after 8 weeks of alternate day fasting. Clinical Nutrition35(6), 1380–1385. https://doi.org/10.1016/j.clnu.2016.03.011
  • 14
    Teruya, T., Chaleckis, R., Takada, J., Yanagida, M., & Kondoh, H. (2019). Diverse metabolic reactions activated during 58-hr fasting are revealed by non-targeted metabolomic analysis of human blood. Scientific Reports9(1). https://doi.org/10.1038/s41598-018-36674-9
  • 15
    Puigserver, A., Wicker, C., & Gaucher, C. (1985). [Molecular aspects of the adaptation of pancreatic and intestinal enzymes to dietary regimens]. Reproduction, Nutrition, Developpement25(4B), 787–801. https://pubmed.ncbi.nlm.nih.gov/2417292/
  • 16
    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
  • 17
    Perez, F., Accarino, A., Azpiroz, F., Quiroga, S., & Malagelada, Juan-R. (2007). Gas distribution within the human gut: effect of meals. The American Journal of Gastroenterology102(4), 842–849. https://doi.org/10.1111/j.1572-0241.2007.01071.x
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.

4 thoughts on “How To Do A 5 Day Fast: The Complete Guide”

  1. I’m on day three of a five day water fast and was looking for information on how to break the fast and get back to eating again. This article was helpful but did not address how long to drink bone broth, green drinks, etc. before moving to solid foods. How long do you do the low calorie veggies before you can go back to meets, cheese, and higher caloric foods? Is it a day, two days? Don’t leave me hanging!

    Reply

Leave a Comment

This site uses Akismet to reduce spam. Learn how your comment data is processed.