Blog Diets 5-Day Water Fast: How To Do It, Benefits, And Dangers

5-Day Water Fast: How To Do It, Benefits, And Dangers

5 day water fast

Humans have been fasting, in one way or another, for thousands of years. While all forms of fasting restrict food intake, some go as far as restricting fluid intake – like the water fast. This type of fast involves taking nothing but water for a period of time – no food, no broth, no juice, no vitamins. Just water.


Although the idea of living this way might seem crazy to some, many have tried water fasting and it has been proven to have several health benefits. But like all things diet, water fasting is not without its dangers. In this article, we look at the 5-day water fast – is it worth it, going for 5 days on nothing but plain water? Here is what you need to know before you embark on a 5-day water fast

What Happens To Your Body On A 5-Day Water Fast?

Water fasting works by helping your body naturally get rid of toxins and impurities. In a nutshell, the process is this: 

Your liver breaks down stored glycogen into glucose (sugar) so that it can be used as fuel for the rest of the body’s cells – this process requires water to happen (8). If no food is consumed, there will be no sugar available from food and all stored glycogen must be burned through oxidation. This means water must be present in order for insulin to bind with cell receptors, which allow glucose uptake into cells. Basically when you’re not eating food your body will use up fat stores first before going after muscle tissue to burn calories in place of sugar/glycogen being burned (4).

The liver will continue to use stored glycogen until it has been depleted. When that happens, the body begins a process called Ketosis, in which your body burns through muscle tissue (and eventually fat) for fuel because glucose is no longer available (9). How long this takes – and what your physical response feels like while you do it – depends on how much muscle mass you have vs. fat mass. Since most of us are made up of more than 50% fat cells (especially if we’re overweight), we start feeling horrible within a few days of doing a water fast with no calories at all.

See also
Strawberry Diets: Fad Or Sustainable Weight Loss Method?

5-day water fast

Read More: How Much Water Should I Drink While Fasting: Estimating Your Fluid Needs

How Long Can A Person Survive On Water?

Can you live on nothing but water for five days? Yes, you can. But it’s not going to be pretty. Your energy level will plummet and your body will start feeling like crap after a few days fat stores are spent and the water fast turns into ketosis. It’s called “hitting the wall” because you experience intense hunger pangs (even though there is no food for the body to convert into calories), weakness, dizziness, nausea, headaches and more that make it feel like you’re about to hit a brick wall if you don’t eat something soon (12).

How To Do A 5-Day Water Fast

There’s a lot of information out there about how to do a 5-day fast, and it can all get overwhelming. Essentially, all this information falls in three categories; the preparation stage, fasting stage, and breaking the fast

Get your personal plan according to your age and BMI
Select your gender
Male Female
Get your personal plan according to your age and BMI
Select your gender
Male Female

How To Prepare For A 5-Day Water Fast

The first thing you need to do is make sure your body is ready for a fast. First of all, if you’re pregnant or have cancer or any other health issue that could be made worse by fasting, please don’t begin this until after consulting with a doctor (7). 

Step 1 – Slowly Cut Back On Food

The best way to prepare the body for a water only fast is to slowly cut back on food. If you normally eat 3 meals per day, start cutting down one meal each week so that in 6 weeks time you will reduce it down to just one meal per day. This gradual reduction makes the transition easier and reduces discomfort during the early stages of the fast.

This slow elimination of calories allows the body time to get used to functioning with less fuel and stores up more energy in the muscles and liver, which are going to be your main energy sources during this type of fast. 

See also
CICO Diet: How It Works, Its Benefits, Risks, And Meal Plan Ideas

Another thing you can do is drink more water during this week prior to the fast. Being hydrated at all times will help control hunger pangs and avoid headaches or lightheadedness during these first few days (15). You also want to stock up on your vitamins, as you won’t be taking any during the 5-day fast. 

Step 2 – Survive During The Fast

Now that we’ve got our bodies prepared for the fast, it’s time to actually start the 5-day water fast. The first 2 days of a fast are usually the hardest, so it’s important to stick to your usual routine, and wait for these feelings to pass. By day two or three you will probably be feeling some fatigue, headaches and muscle weakness. It’s also equally important to listen to your body and rest when you need to. 

During these days instead of thinking about food, spend your energies focusing on staying positive. Try preparing yourself mentally for this change in lifestyle by reminding yourself that after 5 days you will have lost weight and have more energy if done correctly.

Looking for a way to break the vicious cycle of weight loss and tone up all the jiggly parts? Watch the extra pounds fly off and your muscles firm up with the BetterMe app!

5-day water fast

How To Break A 5-Day Water Fast

It’s important to break a long-term water only fast slowly. Doing it any other way puts you at risk of refeeding syndrome – a condition that can be fatal (13). 

To break a 5-day fast you should start with a bone broth or soup. Then gradually start adding foods back into your diet, starting with fresh fruits and vegetables first, and then increasing the calorie content of each meal over the next few days to avoid shock to your digestive system. 

Although you will have lost weight during the fast (around 1-2 pounds per day) if you go from zero calories for 5 days straight into eating whatever you want on day 6, you could actually gain all of that weight back plus more because of how your body reacts to sudden refeeding. Breaking a fast should be done as slowly as possible and with great care. 

See also
7-Day Detox Diet Plan: Can You Rejuvenate Your Body With Food?

Stick to small meals for two weeks. If at any time during this process you feel sick or faint, stop eating until you feel better and consult with a doctor if necessary. 

What Are The Benefits Of A 5-Day Water Fast?

Research has proven several 5-day water fast benefits, including (5):

Weight Loss

Most people who try this fast lose up to 10 pounds or more in just one week of drinking nothing but water. This is expected, because a water fast involves calorie restriction which has been proven to result in weight loss (2). 

However, the weight you lose may come from water, carbs, or worse – muscle. We’ll look at why the 5-day water fast weight loss is problematic in the dangers section of this article. 

May Promote Autophagy

Autophagy is the process in which your body rids itself of dead or damaged cells through a recycling process. It has been studied in animal models and clinical trials, and seems to slow down with age.

Although autophagy occurs naturally even if you are eating normally, it seems more prevalent when a person limits food intake by as much as 30%. Some studies also show that water fasting can help promote autophagy (5).

Autophagy is beneficial for prevention of cancer, Alzheimer’s, and heart disease. Furthermore, this process may help extend one’s life span.

Read More: Lemon Water Health Benefits – Does It Break A Fast?

5-day water fast

May Improve Insulin And Leptin Sensitivity

Leptin is a hormone that tells your body to stop eating, and insulin is what helps the glucose get into your cells during fasting (11). The idea behind water fasting is that you are tricking the body into burning fat stores because there isn’t any sugar available for it to use as fuel.

This will result in your body being more sensitive to leptin and insulin. Being more insulin sensitive means your body is more efficient at reducing its blood sugar levels. Meanwhile, being more leptin sensitive could help your body process hunger signals more efficiently, and in turn, lower your risk of obesity. 

See also
The 3-Day Fruit Diet For Weight Loss: Pros, Cons, And What To Expect

May Lower Blood Pressure 

Studies have shown that water fasting can lower blood pressure in people who suffer from high blood pressure (hypertension) (10). Most of these studies were focused on long fasts of more than 10 days

What Are The Dangers Of A 5-Day Water Fast?

There are several risks associated with an extended water fast, including:

Loss Of Muscle Mass

Before you get excited about your 5-day water fast results, there is something you should know. Not all weight loss is good, especially when you go on a water fast. 

In the absence of food, your body is going to look for some energy and turn to your muscles. Losing lean muscle mass lowers your metabolism and makes weight regain more likely even after you are done with your fast.

If you tend to let yourself off the hook, raise the white flag when things get tougher than you expected, send yourself on an unconscious binge-eating trip – BetterMe app is here to help you leave all of these sabotaging habits in the past!

5-day water fast

Poor Concentration Levels, Poor Memory 

Your mental performance – particularly attention span and memory – will decrease significantly when you’re doing a water fast. This is probably due to decreased glucose levels in the blood (6). 

Dehydration & Orthostatic Hypotension

The symptoms of dehydration can be very unpleasant, including weakness, dizziness, lightheadedness, nausea and more. It’s important to drink water during a water fast to keep you from experiencing these unpleasant symptoms. Because 20-30 percent of your water intake comes from food, you’ll need to compensate with more water (3).

Orthostatic hypotension is a drop in blood pressure that presents as dizziness when you suddenly stand up. It’s common while fasting, and puts you at risk of fainting (1). 

Danger Of Medical Complications 

People with certain conditions can experience drastic disturbances in their body’s acid/base balance by fasting for an extended period of time on just water (14). People with such medical conditions as diabetes, kidney disease, hypothyroidism, chronic infections and ulcers should avoid water fasting altogether! If you are taking any medications or have an ongoing health problem that requires medication – speak with your healthcare provider before attempting a long duration fast.

See also
Pilates Diet Guide: What To Eat Before And After A Pilates Workout

The Bottom Line

Water fasting for five days is not a walk in the park. There are many risks and side effects associated with water fasting, and you should be careful before considering it as an option! However, it can still be useful for autophagy and improving insulin sensitivity among other benefits. If you are curious about doing a 5-day water fast to lose weight or improve health – consult a doctor first, and put some thought into it before deciding if this is right for you.



This article is intended for general informational purposes only and does not address individual circumstances. It is not a substitute for professional advice or help and should not be relied on to make decisions of any kind. Any action you take upon the information presented in this article is strictly at your own risk and responsibility!


  1. Alan Goldhamer, dc: Water Fasting—The Clinical Effectiveness of Rebooting Your Body (2014,
  2. Calorie Restriction and Fasting Diets: What Do We Know? (2018,
  3. Contribution of Water from Food and Fluids to Total Water Intake: Analysis of a French and UK Population Surveys (2016,
  4. Energy Metabolism – an overview (n.d.,
  5. Fasting: Molecular Mechanisms and Clinical Applications (2015,
  6. Fasting: the history, pathophysiology and complications (1982,
  7. Fasting Therapy – an Expert Panel Update of the 2002 Consensus Guidelines (2013,
  8. Glycogen Metabolism – Biochemistry – NCBI Bookshelf (2002,
  9. Ketosis, ketogenic diet and food intake control: a complex relationship. Antonio Paoli et al. 2015 (2015,
  10. Medically supervised water-only fasting in the treatment of hypertension (2001,
  11. Narrative Review: The Role of Leptin in Human Physiology: Emerging Clinical Applications (2011,
  12. Public knowledge of dehydration and fluid intake practices: variation by participants’ characteristics (2018,
  13. Refeeding syndrome: what it is, and how to prevent and treat it (2008,
  14. Renal excretion of uric acid during prolonged fasting (1976,
  15. Water, Hydration and Health (2010,
Get started