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 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 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’ll 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 a 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 seven-day water fast is a diet that excludes all food and caloric beverages for a week, during which time you’re only allowed to consume water to hydrate and cleanse your body. This practice is undertaken for a variety of reasons, such as weight loss, detoxification, spiritual growth, or as a means of resetting your digestive system (10).

A seven-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 may reap more benefits, it also places you at risk of more extreme side effects. This type of fast should only be done under medical supervision. 

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How Do You Do a 7-Day Water Fast?

A fast can support several long-term goals, including weight loss through means of a calorie deficit or autophagy of cells, sensitivity to the hormones insulin and leptin, which play roles in weight management and satiety, blood pressure reduction, a break for the digestive system, and spiritual growth (10). However, a fast, particularly a longer one, can be incredibly dangerous if it’s done incorrectly and it’s not safe for everyone, so you should consult a health professional before you attempt any fasting plan (5). 

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. 

Preparation

The 36-48 hours leading up to a 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 make sure you choose wisely. Eating light, consuming whole foods or ones that have been minimally processed such as fruits and vegetables, and avoiding highly processed foods will allow your body to better capitalize on the benefits of fasting. 

The Fast

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

It’s important to remember that introducing any foods at any point during the seven days will trigger insulin release and effectively break your fast.

• At 12 hours – Around 12 hours of fasting will put you into a state of ketosis where your body starts to break down and burn fat for energy, as opposed to using glucose, a form of simple carbohydrate, as its primary energy source (4).
• At 18 hours – By 18 hours, fat-burning is the primary source of energy, and consequently, you’re generating significant ketones, which replace glucose as your primary energy source. 
• At 24 hours – At 24 hours, it’s 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 and 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 the water fast, insulin will have dropped to its lowest level, and your body will be becoming more sensitive to it. As a result, when food, particularly food that is higher in carbohydrates and simple carbohydrates, is introduced, insulin subsequently rises. Your body will then be quite effective at responding to the insulin increase and bringing nutrients from the blood and into cells.  
• At 72 hours – By the 72-hour mark, your body will start breaking down and generating new immune cells.

Read more: Navigating Intermittent Fasting With A Vegan Lifestyle

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 that occur when the body suddenly goes from a fasted to a fed state. Due to the role of fluids and electrolytes in maintaining the heart’s rhythm, refeeding syndrome can potentially be fatal (15). 

Following a period of extended fasting, without supplementation, your magnesium, potassium, and phosphate stores will be quite 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, particularly with the cardiovascular system. 

Due to the potentially dangerous effects of resuming food intake, it’s imperative to follow a medical professional’s advice closely. A good rule of thumb is to take half the length of the fast to gradually return to your original meal structure. So if you fast for seven days, you should take another 3-4 days to gradually increase your daily meals to their original structure.

During these 3-4 days, certain types of foods can be highly beneficial. Nutrient-dense foods, particularly fruits and vegetables, soft and liquid foods, which can be gentler on the digestive system, and fermented foods, for their probiotics benefitting the gut, should be emphasized. Examples include: 

• 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, are ideal. Due to its balance of macronutrients, this meal can support the stabilization of blood sugar levels and promote calmness. 

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, it’s highly beneficial to eat whole foods (fruits and vegetables are among examples of non-processed foods) and avoid highly processed foods (6). To keep off the weight you’ve lost, it’s highly beneficial to incorporate a workout routine of your choice (12). 

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What Are the Benefits of a 7-Day Water 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. Initially, this is largely due to a deficit in carbohydrates that in turn forces muscles to empty their glycogen, or stored carbohydrate, which leads to a drop in total body water. As a result, a large portion of this initial lost weight will be water, as you’ll first use up all of your stored glycogen, which releases water as it is burned for energy. Subsequent weight loss is largely due to the restricted calorie intake that makes your body burn stored fat for energy (2). 

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 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.

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, as insulin is responsible for bringing sugar from the blood and into the body. Healthy individuals can also experience an insulin spike, particularly if they’re dehydrated after eating a meal or snack that is high in 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 recommended to do so and supervised by their doctor.

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 intermittent fasting to be an effective way to help your liver rejuvenate (7). Research on this subject is still in its infancy, so little is known about it. 

Read more: What is Alternate-Day Fasting? Your Simple Guide to Extreme Intermittent Fasting Regime

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 and weakness. 

Dehydration 

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). 

Electrolyte imbalances caused by the loss of bodily fluids while fasting are also potential side effects, and they can be life-threatening, due to the role of electrolytes in maintaining the heart’s rhythm. Your doctor may recommend taking an electrolyte supplement that contains potassium, calcium, and sodium in order to avoid these very serious consequences.

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’re in a fasting state, the body should start burning fat for energy, but it will use up stored sugar first and 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, how much strength you have, and your metabolism both at rest and during physical activity. 

If you want to lose fat effectively and sustainably, a prolonged fast is not conducive to this goal.

Fatigue

Due to the role of foods, particularly carbohydrates, in supplying the body with energy, a fast can lead to a marked drop in energy. Individuals who are fasting can have significant challenges completing daily activities, particularly those that are more physically demanding and those that require more complex thought. While ketones are an energy source, they are not the brain’s primary energy source nor are they the most efficient energy source for muscles (10). As a result, it can be potentially dangerous to attempt anything that requires significant physical or mental effort during a fast.

FAQs

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

A seven-day water fast can result in an average weight loss of up to 10 pounds (4.5 kg), 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 the weight may return when you resume your regular eating habits, as these physiological changes will be reversed. However, loss in body fat from a fast can be maintained through careful diet and physical activity planning.

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

It’s unlikely that you’ll lose a significant amount of muscle mass during a seven-day water fast. The body generally uses 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 must 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 you must consume enough protein during refeeding periods.

• Is fasting for 21 days healthy?

No, fasting for 21 days is not healthy and can cause quite serious, potentially fatal, health problems. It’s also unnecessary and whatever benefits you hope 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 even death if it’s 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’ve completed the fast.

The Bottom Line

Short-term water fasting can be safe for healthy individuals in the right conditions, as long as medical advice is followed during the fast and when reintroducing foods. Short-term fasting can potentially have many health benefits such as disease prevention, mental clarity, and lower weight, although most of these have not been proven. 

However, fasting can also be dangerous if not performed correctly or when done 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 wish to do the fast as an alternative diet should seek professional advice before starting.