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Blog Nutrition The 7-Day Water Fast Guide: Benefits, Dangers, And Everything Else You Should Know

The 7-Day Water Fast Guide: Benefits, Dangers, And Everything Else You Should Know

7 day water fast

Water fasting is a practice that has been around for hundreds of years. It has grown in popularity as a quick way to lose weight and get healthier. Some water fasting advocates even claim that it can cure cancer, help you live longer, and make your brain function better. However, health experts warn against the dangers of doing a 7 day water fast without supervision.

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This article will cover everything there is to know about this practice. In addition to finding out what a 7 day fast is, you will learn how it works, who should not try it, the risks associated with water fasting for seven days at a time, and also some potential benefits. 

What Is Water Fast?

As its name suggests, a water fast involves consuming no food but only water (10). Some variations of this diet allow unsweetened black coffee and green tea. This helps break the monotony of drinking plain water for a whole week. While on this fast, you’re also allowed to balance electrolytes by licking pure pink Himalayan salt. 

A 7-day fast is more extreme than other types of fasting, such as alternate day fasting and 2-3 day water fasts. While its extended period means you get to reap more benefits, it also puts you at risk of more extreme side effects. 

How To Do A 7-Day Water Fast?

The goal of the long-term fast is to give your body a break and allow it to repair itself. It can be dangerous if done incorrectly, so consult with health professionals before attempting a long-term fasting plan (5). 

Long fasts can result in nutrient deficiency and other physical complications, but knowing how to navigate the seven  days can help you avoid these.

7 day water fast


The 48-36 hours leading up to the water fast is important to get your body and mind prepared for what is to come. Attempting a 16-hour fast for the day or two before will give your body time to adjust and then reduce the intake of energy-intensive food

What you eat before the fast can make or break how successful the next few days of fasting are, so be sure to choose wisely. Eating light, consuming whole food (fruits and vegetables), and avoiding having processed foods will allow your body to better capitalize on the benefits of fasting.

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

The Fast

What are the phases of a 7-day water fast? Here’s what happens in your body during the fast. 

Remember, introducing any foods at any point during the seven days triggers insulin release and effectively breaks your fast.

  • At 12 hours – 12 hours fasting will put you into a state of ketosis, in which your body starts to break down and burn fat (4).
  • At 18 hours – By 18 hours, you’ve switched to fat-burning mode and are generating significant ketones. 
  • At 24 hours – At 24 hours, your cells are recycling old components and breaking down misfolded proteins linked to diseases such as Alzheimer’s. This process is called autophagy which starts immune system regeneration (1).
  • At 48 hours – By the second day of fasting, your growth hormone level has increased by up to five times.
  • At 54 hours – By around 60 hours into water fast, insulin has dropped to its lowest level, and your body is becoming more sensitive to it. A person with type 2 diabetes would benefit from this, as their body re-sensitizes itself to insulin.
  • At 72 hours – By the 72-hour mark, your body will start breaking down and generating new immune cells.
7 day water fast dangers

The Refeed

Knowing what to eat after a 7-day fast can make a lot of difference. Eating too much too soon puts you at risk of refeeding syndrome– a set of symptoms caused by changes in electrolytes and water balance (14). 

After a period of extended fasting, without supplementation, your magnesium, potassium, and phosphate stores are very low. As you start consuming food again, and your body starts processing macronutrients, especially carbohydrates, your body requires those same minerals to process the food. Eating a lot of food right away can cause a large drop in blood potassium levels and thus lead to serious complications. 

A good rule of thumb is to take half the time of the fast to ease back into eating. So if you fast for seven days, you should take another 3-4 days to break the fast.

During the 3-4 days, break your fast with these foods:

  • Fermented foods like unsweetened yogurt and kefir
  • Clear bone broth
  • Diluted vegetable juice without the pulp

After the first 3-4 days, eat a small refeed meal made up of a balance of carbohydrates, proteins, and fats. Some lean protein like salmon and fibrous vegetables like broccoli would be ideal. This meal will help stabilize blood sugar levels and keep you calm.

7 day water fast dangers

The Aftermath

Once the week is over, take some time to rest before consuming normal amounts of food. Start with small portions and gradually increase them to your normal consumption. When you do, eat whole foods (fruits and vegetables) and avoid unhealthy processed foods (6). To keep off the weight loss, you’ll also have to incorporate a workout routine of your choice (11).

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What Are The Benefits of A 7-Day Fast?

Several studies have shown the following benefits of extended fasting:

Weight Loss

In addition to the boost in metabolism that comes from water fasting for seven days at a time, some studies show that it can help you lose up to 1 pound per day. This is largely due to the restricted calorie intake that makes your body burn stored fat for energy (2).

7 day water fast weight loss

Autophagy (Rebuild Your Body)

Autophagy is a process by which your body breaks down old cells and rebuilds them as needed through natural cell death (1). Interestingly, a long-term fast appears to kill off short-lived immune system cells in the body called “plasmacytoid dendritic cells.” These immune cells tend to live for just 2-3 weeks before being replaced by newer ones. It’s suggested that when these older cells die off, newer cells are better equipped to respond to vaccination. 

The effects of autophagy have been studied extensively in cancer patients during chemotherapy treatment (15). It seems that with each round of chemo, cancer returns. However, those who have fasted regularly display higher levels of “cleaner” cells and fewer malignant tumor cells than those who have not fasted. 

This is due to autophagy which rebuilds immune system cells and destroys faulty ones. This means that cancer patients undergoing chemo or radiation can benefit from this type of diet (3). It can cause them to live longer and feel better during treatment while also helping them heal once it has ended. 

The benefits of autophagy are not restricted to patients; even healthy people can experience them too.

7 day water only fast

Regulate Insulin Levels

High sugar diets are notorious for their ability to raise blood sugar rapidly in some people, especially type 2 diabetics. This change in blood sugar levels is often followed by an insulin spike. Healthy individuals can also experience this, especially if they are dehydrated after just eating a meal or snack that contains simple carbohydrates like sugars and white flour products.

Fasting helps lower insulin levels and stabilize them. After fasting for 72 hours, insulin sensitivity increases significantly compared to non-fasting scenarios (9).

Read More: Bulletproof Coffee Fasting: Should You Say No To Keto Coffee When You’re On A Fast

Quality of Sleep

Fast days provide the body time to repair cells, restock nutrients and rebuild energy sources that are depleting as a result of daily activity. A 7-day fast can improve sleep quality by reducing cortisol levels which cause an imbalance of energy in the body. 

Cortisol is a hormone that helps the body cope with stress by increasing blood pressure, blood sugar, and metabolism. However, the constant production of cortisol can be damaging to cells if it occurs too frequently or for too long (12).

Water fast allows the body time to rest and repair itself, which results in lower levels of cortisol in your bloodstream.

7 day water fast exercise

Liver Rejuvenation

Your liver needs a break now and then too, and doing a 7-day water fast could help you with that task. Some studies show fasting can be an effective way of helping your liver rejuvenate (7). The research on this subject is still in its infancy stages, so there isn’t much more known about it just yet. 

What Are The 7-Day Water Fast Dangers?

There are many potential side effects to a 7-Day Water Fast, including rapid heartbeat, dizziness, and fatigue. The two  most severe side effects are dehydration and muscle loss/weakness.

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It might seem impossible, but you can be dehydrated while on a water fast, especially if the fast continues for an extended period. Dehydration can lead to dizziness, weakness, muscle cramping, disorientation, and more severe symptoms in extreme cases (13). 

Electrolyte imbalances caused by the loss of bodily fluids during fasting are also possible side effects. This can be easily remedied by taking an electrolyte supplement that contains potassium, calcium, and sodium.

7 day water fast guide

Muscle Loss

Reversing muscle loss is one of the main concerns for those who are curious about how to do a 7-day water fast to lose weight. Muscle is very important for your body because it helps it burn calories efficiently (8). 

Theoretically, in a fasted state, the body should start burning fat for energy and use up stored sugar first before beginning to break down muscle tissue. The 7-day water fast weight loss should be fat, but some of it can be muscle. Muscle loss is a major concern as it can lead to changes in the way your body looks and how much strength you have. 

People who are trying water fasting as a weight loss diet should have their urinalysis checked to confirm they are producing ketones, not breaking down muscle tissue.

Intermittent Fasting According To The Age

The Bottom Line

Water fasting is safe for healthy individuals under the right conditions. It comes with many health benefits such as improved sleep, mental clarity, and lower weight. 

However, it can also be dangerous if not performed correctly or by those who have certain medical conditions. Fasting for seven days should only be attempted under supervision by a doctor, and those who have medical concerns or are trying to do the fast as an alternative diet should seek professional advice before beginning.

If you are interested in healthy meal plans, you may be curious about other methods of supporting your body health. Supplement a proper meal plan with some exercise and take up this 20 Min Full Body Workout at Home.

See also  Best Foods For PCOS: Eat This To Help Manage Your Condition


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. Autophagy: cellular and molecular mechanisms (2010,
  2. Calorie Restriction and Fasting Diets: What Do We Know? (2018,
  3. Fasting: Molecular Mechanisms and Clinical Applications (2015,
  4. Fasting: the history, pathophysiology and complications (1982,
  5. Fasting Therapy – an Expert Panel Update of the 2002 Consensus Guidelines (2013,
  6. Healthy Eating for a Healthy Weight (2021,
  7. How intermittent fasting changes liver enzymes and helps prevent disease: Research on mice reveals surprising impact on fat metabolism (2020,
  8. Increasing muscle mass to improve metabolism (2013,
  9. Intermittent fasting dissociates beneficial effects of dietary restriction on glucose metabolism and neuronal resistance to injury from calorie intake (2003,
  10. Is fasting safe? A chart review of adverse events during medically supervised, water-only fasting (2018,
  11. Physical Activity for a Healthy Weight (2020,
  12. Physiology, Cortisol – StatPearls – NCBI Bookshelf (2021,
  13. Public knowledge of dehydration and fluid intake practices: variation by participants’ characteristics (2018,
  14. Refeeding syndrome: what it is, and how to prevent and treat it (2008,
  15. The Role of Autophagy in Cancer and Chemotherapy (2016,
Jeremy Mukhwana
Jeremy Mukhwana

Jeremy is a writer and part-time soccer player who is keen on demystifying the matters of fitness, health, and weight loss. His articles are focused on providing factual information and helping readers enjoy their fitness journeys. He understands that wellness is an often misunderstood yet deeply rewarding avenue of improving one’s life, which is why he is so committed to encouraging people to live their healthiest lives through his work. When he’s not typing away at his keyboard, he’s indulging his passion for soccer. The motto that guides Jeremy through his life is  ‘Be the change that you wish to see in the world.’

J. Paul
J. Paul

Jovial is from Dubai, and is a Head EMS Instructor/Fitness Manager/Nutrition Consultant for REMS Fitness. He is certified by the Gold’s Gym Fitness Institute and Registered as a Gym Instructor.
Jovial specialises in HIIT training, Rehabilitation/injury recovery, Strength and Conditioning, Kickboxing, Body Weight Training and Weight Training, and practices each discipline himself. His approach is to focus on improving his clients’ lifestyle by motivating them and setting an example.

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