Blog Nutrition 72-Hour Fast: Benefits And Dangers Of A Long Water Fast

72-Hour Fast: Benefits And Dangers Of A Long Water Fast

Intermittent fasting is a form of dieting that involves alternating between periods of eating and periods of not eating. In the case of water fasting, it means drinking only water for some time. The length can vary from 12 hours to 72 hours, depending on what you want to achieve.

Water fasting has been around for centuries, and many records show its use in ancient civilizations. It is still used today for many different reasons.

Intermittent fasting is generally safe and healthy, with only a few limitations: it is not encouraged to those who are underweight (BMI < 18.5); pregnant or breastfeeding women should not do it at all; diabetics or those with other medical conditions should consult their doctors before doing it; children and adolescents should never attempt to fast.

The Five Stages Of Intermittent Fasting

When your body perceives environmental stress (such as a limited food supply), it adjusts the activity of genes that are relevant in defending you from stress as a result of intermittent fasting. The changes occur in five stages depending on how long you fast:

At 12 Hours – Ketosis 

In the first stage, which lasts from 12 to 18 hours after your last meal, your body has used most of its available carbohydrates for energy and starts  burning fat, as well as converting protein into energy. During this period, a large number of fats are released into the bloodstream and converted into a fuel known as ketones (9). When this happens, you experience a state called ketosis.

At 18 Hours – Fat Burning Mode

In this stage, which is from 18 to 24 hours after your last meal, your body starts using ketones as its primary source of energy. In addition to breaking down fats in the process known as beta-oxidation, your liver begins producing ketones that are actually used by your brain, which normally gets its energy from glucose (16). When this happens, some people say that they feel more focused and energized than ever before. Others experience difficulty concentrating or “brain fog”.

At 24 Hours – Autophagy 

During stage three, which lasts from 24 to 48 hours after your last meal, autophagy is believed to be happening at its peak level. This process is an important mechanism for maintaining health as it recycles cellular components like amino acids to make new proteins and mitochondria (the powerhouses of cells) and make new energy for your body cells (2). It also breaks down defective proteins in the cell to prevent them from accumulating inside the cell, which may lead to degenerative diseases like cancer and Parkinson’s Disease. Research indicates that fasting can trigger autophagy and that this happens around the 24-48 hour timeframe, but most studies have been done in animals.

See also
18 Allspice Benefits For Health, Weight Loss, And More

At 48 Hours – Growth Hormone 

The fourth stage, which occurs from 48 to 54 hours after your last meal, is when hormones such as human growth hormone (HGH) and noradrenaline increase dramatically (1). These hormones may play an important role in the growth and improvement of your overall health by preventing heart attacks, strokes, and diabetes and speeding up the repair process for damaged cells.

7 day water fast weight loss

At 72 Hours – Cell Regeneration 

Animal and in vitro studies suggest that prolonged fasting may promote stem cell regeneration.  Theoretically, because autophagy has been activated, old and defective cells have been removed from the system (20).

In addition, fasting may result in  a general decrease in inflammation and improved insulin sensitivity which brings about a variety of health benefits such as the reduced risk of chronic diseases.

Read More: 21-Day Fasting Diet to Improve Spiritual Well-Being

How To Do A 72-Hour Fast?

72-hour water fast quite simply involves not eating and only drinking water for 72 hours. You’re also allowed to drink unsweetened black coffee and green tea to break up the monotony of plain water.

What To Eat After A 72-Hour Fast?

After going without food for days, you’re excited and relieved when it’s time to eat. However, you have to be very careful when breaking your fast. Choose a meal that’s gentle on your stomach and good for your metabolism. 

Here’s how to break a 72-hour fast with the right foods:

Bone Broth

Bone broth contains numerous vitamins and minerals, as well as amino acids and other components that can help the body and gut function optimally post-fast. This makes it an ideal first meal to have as you slowly ease into eating meals. 

See also
Mustard Greens Benefits, Nutrition Facts, Side Effects, And Meal Ideas

Bone broth also contains gelatin, a protein that can help heal a ravaged digestive system by providing possible anti-inflammatory effects (6).


Poultry or fish are ideal post-fast protein choices. Protein is made up of building blocks called amino acids and is essential for building healthy body cells (3). Steamed or baked salmon or chicken is a great addition to your plate while you’re easing back to eating solid foods

Non-Starchy, Non-Cruciferous Vegetables

Since vegetables contain important vitamins and nutrients that your body needs to post fast, having a portion of greens is ideal. Make sure to avoid cruciferous vegetables like broccoli and cauliflower while fasting because they can cause gas after a prolonged period of not eating solid food. Use leafy greens like spinach and bok choy, saute them in healthy fats to make them easier for your stomach to digest.


72 hour fast

Foods To Avoid After A 72-Hour Fast

Eating these foods might cause discomfort, gas, bloating, diarrhea, or constipation, so it’s best to avoid them until you have fully transitioned from your fasted state:

Processed, High-Glycemic Carbs

This includes crackers, chips, white bread, and other refined carbohydrates. These foods are broken down quickly by the body and raise blood sugar levels, which may be a shock to your system after a few days of not eating (5).


Milk contains lactose (sugar), which can irritate your stomach and cause bloating (17). If you’re not lactose intolerant, you might be able to indulge in one to two servings of dairy post-fast as long as it’s properly digested. In general, though, stay away from most forms of dairy until you’ve fully transitioned from fasting mode.

Cruciferous Vegetables

Broccoli, kale, cauliflower, and cabbage contain indigestible carbohydrates which are fermented by your gut bacteria,  causing gas. These veggies are nutrient-dense, so you should have them after breaking your fast if you tolerate them well. Just ease your way into enjoying them again.

BetterMe is your fast-track ticket to a long-lasting weight loss! Tailor your fitness journey and maximize your results with just a couple of swipes!

Tips For Surviving A 72-Hour Fast

The first few days of fasting can be very tough psychologically. Lack of food over an extended period is an extremely unnatural situation that puts extra stress on the body. 

See also
Quick Antioxidant Smoothie Recipes For Improved Immunity

Here are two tips to help ease your mind during this process: 

Stay Hydrated

Drink plenty of water during your fast. Without food, the body relies on stored energy in the form of glycogen, which holds onto water. As glycogen is depleted during fasting, your body will give up its water stores. Drinking plenty of water while fasting not only helps prevent dehydration but also reduces hunger significantly (23). You’ll need to get electrolytes from fluids as well, since you won’t be getting them from foods during this time.

Keep Busy

You’re more likely to think about food if you’re bored. Keep yourself occupied with activities that take your mind off food. This might include exercise, reading, taking a walk, or spending time with friends and family.

Ease Hunger Pangs With Black Coffee

Drinking coffee breaks up the monotony of having plain old water all day. It’s also a mild appetite suppressant that can help you get through cravings for junk food or sweets (4). However, remember that too much caffeine will dehydrate you further, so limit your intake to two cups maximum per day while fasting to avoid this problem. 

Break Your Fast Gently And Slowly

Your stomach needs time to adjust to digesting solid foods again, so easing back into eating is very important. Eat small amounts of simple meals for the first couple of days until you feel ready to go back to normal portions. Overstuffing your body post-fast can cause nausea, vomiting, or cramps, which defeats the purpose of fasting altogether.

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

Read More: Low-Carb Intermittent Fasting- Everything You Need To Know


Benefits Of 72-Hour Fasting

Both human and animal studies have linked water fasting to a variety of health benefits, including:


This is a physiological mechanism that involves the formation and activation of macroautophagy and other related intracellular processes known as autolysosomes (8). It is the process by which your body breaks down and recycles old or damaged cellular materials. It is believed that fasting can trigger autophagy, but this has mostly been studied in animals.

Blood Glucose

Levels of insulin become more stable while blood sugar levels decrease, which may result in improved regulation of metabolism and overall weight reduction.

See also
Just Beet It: The Multiple Health Benefits Of Beetroot Juice, Explained


HDL cholesterol has been seen to increase and triglycerides to decrease significantly, reducing risk for cardiovascular diseases such as atherosclerosis (21).

DNA Repair

It is believed that the metabolic adaptations to the stress of fasting may help prevent DNA damage (8).

Heart Health

A study involving obese individuals with metabolic syndrome found that three days of fasting using only water resulted in weight reduction, improvement of heart health markers, and lower levels of C-reactive protein (CRP), which is a marker for inflammation (14). 

Immune System Function

Fasting may help improve the immune system by regenerating stem cells so they can rebuild damaged tissue more quickly (20). This could potentially result in improved recovery time after an illness or injury, as well as a lower risk of chronic diseases.

Insulin Sensitivity

One study on type 2 diabetes patients showed that these individuals have an increased insulin sensitivity after fasting. The results were attributed to the normalization of blood glucose levels since there’s a lower need for insulin production and improved function of the pancreas (15). People with diabetes or other medical conditions should not fast without first consulting with their doctor.


Animal studies have suggested that cycles of fasting may extend have beneficial effects on longevity, aging, and disease (13). Much research still needs to be done to fully understand the effects of fasting on humans.

Weight Loss

Studies show that intermittent fasting can lead to significant weight loss as effectively or more so than conventional diets or simply restricting calories alone (12).

If you’ve mustered up the courage to crush your weight loss goal, let Betterme take the sting out of this demanding process. Our app will help you restructure your habits, remold your life and crank up your fitness results!

72 hour fast

Water Fasting Dangers

Even though water fasting has its benefits, it’s not advisable for everyone. 

Here are some of the dangers of 72-hour water fast:


Some of our water and most of our electrolytes come from food, so fasting can reduce how much of both you’re getting every day. Dehydration can cause dizziness and severe headaches, as well as health conditions such as kidney damage (23).

See also
How Many Calories in a Banana? And the Secret to Losing Weight With Bananas

Orthostatic Hypotension

This is a major problem for those who suffer from heart disease since water fasting may result in a temporary decrease of blood pressure due to lack of food intake, causing fainting (18). 

Worsen Medical Conditions

There are a few conditions that may be aggravated by water fasting. These include:

  • Gastrointestinal Issues

 Those suffering from stomach ulcers, colitis, and Crohn’s disease may not be able to fast without experiencing nausea and diarrhea as well as abdominal pain.

  • Gout

Water fasting increases uric acid production, which may cause an acute gout flare-up (22).

  • Hypertension

Hypertensive Individuals should also avoid prolonged periods of water fasting to prevent severe health conditions such as heart attacks and strokes.

  • Heart Disease

The lack of food intake during a long time, like 72 hours without any food, could result in an irregular heartbeat that can cause serious heart problems.

People who suffer from any of these listed conditions or illnesses should not fast for 72 hours:

  • Alzheimer’s disease
  • Chronic fatigue syndrome
  • Eating disorders
  • Diabetes
  • Gastrointestinal diseases such as abdominal pain, heartburn, and irritable bowel syndrome (IBS)
  • Metabolic disorders like high cholesterol levels, high blood pressure, etc. should consult with their doctor first

Individuals who are pregnant or breastfeeding should also avoid water fasting since it can cause malnutrition or affect the development of their unborn child or infant (10). Those with heart disease and kidney failure patients on dialysis shouldn’t consider water fasting at all unless they seek advice from a health care provider first.

Experts recommend that children and teenagers under 18 years old should avoid water fasting since their bodies need more nutrients than adults for proper development.

The Bottom Line

Water fasting can be an effective way to lose weight and may even add more years to your life. But it shouldn’t be done without thorough research on what you can and cannot do, especially if you have any medical conditions or take medication regularly. If you’re planning to try water fasting for 72 hours, make sure that you tell your healthcare provider about it in advance and avoid doing so if you suffer from any of the conditions mentioned above.


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. Augmented growth hormone (GH) secretory burst frequency and amplitude mediate enhanced GH secretion during a two-day fast in normal men (1992,
  2. Autophagy: cellular and molecular mechanisms (2010,
  3. Biochemistry, Essential Amino Acids – StatPearls – NCBI Bookshelf (2021,
  4. Caffeine, coffee, and appetite control: a review (2017,
  5. Carbohydrates and Blood Sugar | The Nutrition Source | Harvard TH Chan School of Public Health (n.d.,
  6. Collagen and gelatin (2015,
  7. Effect of Alternate-Day Fasting Among Metabolically Healthy Obese Adults (2017,
  8. Fasting: Molecular Mechanisms and Clinical Applications (2014,
  9. Fasting: the history, pathophysiology and complications (1982,
  10. Fasting during Ramadan Increases Risk of Very Preterm Birth among Arabic-Speaking Women (2019,
  11. Fasting enhances growth hormone secretion and amplifies the complex rhythms of growth hormone secretion in man (1988,
  12. Fasting for weight loss: an effective strategy or latest dieting trend? | International Journal of Obesity (2015,
  13. Intermittent and periodic fasting, longevity and disease (2021,
  15. Intermittent fasting dissociates beneficial effects of dietary restriction on glucose metabolism and neuronal resistance to injury from calorie intake (2003,
  16. Multi-dimensional Roles of Ketone Bodies in Fuel Metabolism, Signaling, and Therapeutics (2017,
  17. Nutrients | Free Full-Text | Lactose Intolerance, Dairy Avoidance, and Treatment Options (2018,
  18. Preventing and treating orthostatic hypotension: As easy as A, B, C (2010,
  19. Progressive alterations in lipid and glucose metabolism during short-term fasting in young adult men | American Journal of Physiology-Endocrinology and Metabolism (1993,
  20. Prolonged Fasting Reduces IGF-1/PKA to Promote Hematopoietic-Stem-Cell-Based Regeneration and Reverse Immunosuppression: Cell Stem Cell (2014,
  21. Randomized cross-over trial of short-term water-only fasting: Metabolic and cardiovascular consequences (2013,
  22. Renal excretion of uric acid during prolonged fasting (1976,
  23. Water, Hydration and Health (2010,
150 million people
have chosen BetterMe

I've struggled to maintain programs…

I've struggled to maintain programs before, but somehow I've been able to stick with this. I enjoy the workouts and have made healthy changes to my diet with the challenges. Its nice for something to really have stuck and worked. I did the sugar free challenge and it's really changed how I relate to the signals my body is giving me about the food I'm eating.

Our Journey

This has been an awesome journey for my wife and I. Not only are we losing weight , but we are living a new life style. Our eating habits have been reformed by following the meal plan and our bodies have become stronger by simply doing the ten minute, sometimes twenty minute workouts. It really has been easy and convenient to transition into a healthier routine and has truly re energized our lives moving forward into the future.

It Works! This program is working for me!

lynne R.
This program is working for me! After a little over a month, I have lost 10 pounds. Slow, but steady. Guided exercises are done daily and there is an option to do other routines beside the one chosen for the day. It is very helpful having the recipes for all meals plus a snack. Would like if we could know the ingredients the day before. Makes preparing alot easier. I like the fact that alternative foods are suggested in case you can't eat(or don't like) the recipes listed. This is a very good program. Stick to it and YOU will see results. I have!