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

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

This article covers everything you need to know about this practice. In addition to finding out what a seven-day fast is, you will learn how it works, who shouldn’t try it, the risks associated with water fasting for seven days at a time, and the potential benefits.

What Is Water Fast?

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

What Is A 7-Day Water Fast?

A 7-day water fast is a diet that excludes all food and caloric beverages for a week, during which you are only allowed to consume water to hydrate and cleanse your body. This practice is undertaken for various reasons, including weight loss, detoxification, spiritual growth, or as a means to reset one’s digestive system.

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 might reap more benefits, it also puts you at risk of more extreme side effects. This type and duration of fast should only be done under medical supervision.

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. However, it can be dangerous if done incorrectly and it isn’t safe for everyone, so you should consult a health professional before attempting any fasting plan (5). 

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


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

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

7 day water fast

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 – Around 12 hours fasting will put you into a state of ketosis, in which your body starts to break down and burn fat for energy (4).
  • At 18 hours – By 18 hours, you’ve switched to fat-burning mode and are generating significant ketones, which replace glucose as your primary energy source. 
  • At 24 hours – At 24 hours, it is believed that your cells are recycling old components and breaking down misfolded proteins such as those linked to diseases like Alzheimer’s. This process is called autophagy which starts immune system regeneration (1).
  • At 48 hours – By the second or third day of fasting, your growth hormone level may have 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.
  • At 72 hours – By the 72-hour mark, your body will start breaking down and generating new immune cells.
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The Refeed

Knowing what to eat after a seven-day fast can make a lot of difference. Eating too much too soon puts you at risk of refeeding syndrome, a dangerous set of symptoms caused by rapid changes in electrolytes and water balance (15). 

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

Follow whatever instructions your doctor gives you, but 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 these 3-4 days, you should break your fast with these foods:

  • Fermented foods such as unsweetened yogurt and kefir
  • Clear bone broth
  • Diluted vegetable juice without pulp

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

The Aftermath

Once the week is over, you should take some time to rest before you consume normal amounts of food. Start with small portions and gradually increase them to your normal consumption level. When you do this, you need to eat whole foods (fruits and vegetables) and avoid highly processed foods (6). To keep off the weight you have lost, you’ll also need to incorporate a workout routine of your choice (12). 

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7 day fast

What Are The Benefits of A 7-Day Fast?

The benefits of a seven-day water fast include weight loss, cell regeneration (autophagy), regulation of insulin levels, and liver rejuvenation, all of which result from low caloric intake and the absence of sugars (10).

Weight Loss

Some studies have shown 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). A good portion of this weight will be water, as you will first use up all of your stored glycogen, which releases water as it is burned for energy.

Autophagy (Rebuild Your Body)

Autophagy is a process through which your body breaks down old cells and organelles and rebuilds them as required through natural cell death (1). 

The effects of autophagy have been studied extensively in cancer patients during chemotherapy treatment (16). It appears that autophagy can be either pro- or anti-tumor and that it can potentiate the cytotoxicity of chemotherapy drugs, but it has also been linked to drug resistance. As with many interactions and processes that we don’t yet fully understand, further research is required.

The potential benefits of autophagy are not limited to cancer patients and some healthy people are drawn to the idea of self-renewal in the belief that it may help prevent aging and disease. It’s mostly theory at this point, but autophagy and its relationship with fasting is an intriguing area for future research.

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Regulate Insulin Levels

High-sugar diets are notorious for their ability to increase blood sugar levels rapidly in some people, particularly those with type 2 diabetes. This change in blood sugar levels is often followed by an insulin spike. Healthy individuals can also experience this, particularly if they’re dehydrated after eating a meal or snack containing simple carbohydrates such as sugars and white flour products.

Fasting may help lower insulin levels and stabilize them. However, people with diabetes should not fast unless they are recommended to do so and supervised by their doctor.

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

Liver Rejuvenation

Your liver needs a break every now and then, and doing a seven-day water fast may help you with this. Some studies in animals have shown that intermittent fasting can be an effective way to help your liver rejuvenate (7). Research on this subject is still in its infancy, so there isn’t much known about it just yet.

7 day water fast guide

What Are The 7-Day Water Fast Dangers?

There are many potential side effects to a seven-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 may seem impossible, but you can become dehydrated while on a water fast, particularly if the fast continues for an extended period. Dehydration can cause dizziness, weakness, muscle cramping, disorientation, and more severe symptoms in extreme cases (14). 

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Electrolyte imbalances caused by the loss of bodily fluids while fasting are also possible side effects and they can be life-threatening. Your doctor may recommend you avoid this by taking an electrolyte supplement containing potassium, calcium, and sodium.

Muscle Loss

Reversing muscle loss is one of the main concerns for those who are curious about how to do a seven-day water fast to lose weight. Muscle is incredibly important for your body as it allows you to move and perform daily activities. It also helps you burn calories efficiently (8). 

Theoretically, when you are in a fasting state, the body should start burning fat for energy, but it will use up stored sugar first and also break down muscle tissue to turn the protein into glucose. Seven-day water fast weight loss will most likely be at least in some part muscle. Muscle loss is a major concern as this can lead to changes in the way your body looks and how much strength you have. 

If you want to lose fat effectively and sustainably, a prolonged fast is not the answer.

7 day water fast result


  • How much weight can I lose on a 7-day water fast?

A seven-day water fast can result in a weight loss of up to 10 pounds (4.5 kg) on average, but this may vary depending on individual factors such as starting weight and body composition.

The majority of this weight loss will be water weight. As you fast, your body uses up stored glycogen for energy, which is bound to water molecules (17). In addition, the elimination of processed foods and excess sodium intake can contribute to a significant drop in water weight.

This weight loss may not be sustainable and may return when you resume your regular eating habits.

  • Will I lose muscle if I fast for 7 days?

It’s unlikely that you will lose a significant amount of muscle mass during a seven-day water fast. The body is designed to first use up stored glycogen and fat for energy before it turns to muscle tissue.

However, it should be noted that prolonged fasting can lead to some muscle loss if you don’t take proper precautions.

The process of muscle loss, which is referred to as muscle wasting or atrophy, occurs when the body breaks down muscle tissue to use as fuel. For this to happen, the body needs to be in a state of prolonged fasting or starvation (11).

To prevent muscle loss, you shouldn’t extend your water fast beyond seven days, and make sure you consume enough protein during refeeding periods.

  • Is fasting for 21 days healthy?

No, fasting for 21 days is not healthy and can cause serious health problems. It’s also unnecessary and whichever benefits you’re hoping to achieve can be accomplished on shorter fasts.

The recommended maximum duration for a water fast is seven days, after which time you should gradually reintroduce solid foods into your diet.

Prolonged fasting can cause electrolyte imbalances, nutrient deficiencies, weakened immune system, and other health issues if it is not monitored properly.

  • Should I work out during a 7-day fast?

The only workouts that are recommended during a seven-day water fast are light exercises such as walking or gentle yoga. Intense workouts should be avoided as your body will be in a state of energy conservation and may not have enough fuel to sustain high-intensity activities.

In addition, excessive physical activity can increase the risk of dehydration and other health complications.

If exercise is important to you, it’s best to plan your seven-day water fast during a period of rest and avoid strenuous workouts until you have completed the fast.

The Bottom Line

Short-term water fasting can be safe for healthy individuals in the right conditions. It claims to have many health benefits such as disease prevention, mental clarity, and lower weight, although most of those have not been proven. 

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


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. Muscle atrophy (2021,
  12. Physical Activity for a Healthy Weight (2020,
  13. Physiology, Cortisol – StatPearls – NCBI Bookshelf (2021,
  14. Public knowledge of dehydration and fluid intake practices: variation by participants’ characteristics (2018,
  15. Refeeding syndrome: what it is, and how to prevent and treat it (2008,
  16. The Role of Autophagy in Cancer and Chemotherapy (2016,
  17. Water Fasting Is Almost Always a Really Bad Idea (2023,
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