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Home arrow Nutrition arrow Intermittent Fasting arrow 5-Day Fast: What to Know Before You Start

5-Day Fast: What to Know Before You Start

Dr. Donika Vata
Written by Donika Vata, MD
Fact checked by Edna Skopljak, MD
Last update: October 17, 2023
9 min read 840 Views 0 Comments
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A 5-day fast is a type of prolonged fasting that can help your body in multiple ways. Read on to discover how to minimize the risks associated with a 5-day fast to reap its benefits.

5 day fast

Fasting, an ancient practice of restricting food that dates back thousands of years, offers not only physical benefits but also promises to improve mental well-being. This enduring approach has captivated the United States and brought intermittent fasting to the forefront of popular dieting methods. This particular fasting technique involves abstaining from caloric intake for a set period of time.

Among the many fasting protocols, the 5-day fast stands out as a preferred choice for experienced practitioners. While it may seem demanding at first, the health rewards are substantial. However, it is crucial to approach this fasting endeavor with proper care and precision.

Let’s now delve into the realm of the 5-day fast, explore what it entails, and unravel the proper way to embark on this transformative journey.

What Is a 5-Day Fast?

A 5-day fast is a prolonged fasting method that requires you to stop consuming all types of food and caloric beverages. It means that you need to rely only on water and electrolytes for 5 days.

It allows your body to get rid of contaminants that hinder the natural healing process. In addition, it can also help you lose weight, regulate high blood pressure, and improve cardiovascular health.

It’s important to note that a 5-day water fast might not necessarily be a comfortable experience. It’s especially true if you haven’t tried prolonged fasting before.

Other than food cravings, you’ll also experience a drop in energy levels as your body burns up its fat supply. But luckily, you can minimize this unpleasantness by using the water fasting technique discussed below.

How to Do a 5-Day Fast?

Let’s discuss a detailed process on how you can start and end a 5-day fast successfully.

Cut back on food gradually

To start a successful 5-day fast, you should begin by gradually reducing your food intake. Instead of having three meals a day, try having two for about a week.

It’ll decrease your calorie intake, and your body will start using muscle and liver glycogen for energy. This way, you’ll allow your body to adjust and minimize discomfort.

Additionally, you should also increase your water intake during this time. It’ll regulate appetite, prevent headaches, and avoid dizziness.

Don’t forget to stock up on vitamins before the fast since you won’t be able to take them during the five days.

Important note: You can also try a fasting-mimicking diet or intermittent fasting first. They make for easy fasting options and can help you prepare your body for a 5-day fast.

Get through the fast

To complete a 5-day fast successfully, it’s important to drink a lot of water and stay hydrated. But relying only on water can lead to overhydration and electrolyte imbalance. To prevent this from happening, you’ll need to increase your electrolyte consumption.

The simplest way to meet your electrolyte needs is to add a pinch of pink salt to your teas. You can also buy electrolyte-enriched water or supplements for the same purpose.

Choose your drinks wisely to make sure that you meet the daily recommended dose of electrolytes.

Daily recommended electrolyte dosage

Here’s the daily recommended dosage of electrolytes and water for adults over 18 years of age:

  • Water: 72 and 104 ounces (for women and men, respectively)
  • Sodium: 1,500mg
  • Potassium: 4,700mg
  • Magnesium: 320 and 420mg (for women and men, respectively)

Pro tip: You can also consume unsweetened teas to feel satisfied for a longer time.

Break a 5-day fast slowly

When ending a 5-day fast, it’s important to reintroduce food slowly. Start with light and easily digestible options such as soups, smoothies, fruits, and vegetables.

Spend at least two days eating these light food options to help your body adapt. For the first meal after the fast, consider a smoothie or protein shake. You can pair it with vegetable broth or bone broth and a fermented drink of your choice.

Your goal is to gradually increase your caloric intake to avoid shock to your digestive system. Focus on these options for a few days to help your body adjust smoothly after a 5-day fast.

Benefits of Fasting for 5 Days

Now that you understand how to fast for 5 days, let’s discuss the benefits of this fasting method.

#1 Blood sugar control

When you’re fasting, hormones like insulin and leptin play important roles. Leptin signals your body to stop eating, while insulin sends all the glucose into your body’s cells.

By depriving the body of sugar, fasting encourages the use of fat reserves for energy. This process can increase your body’s sensitivity to both leptin and insulin.

Improved insulin sensitivity helps lower blood sugar levels more effectively. While increased leptin sensitivity can manage hunger signals better and reduce the risk of weight gain.

#2 Fights inflammation

According to scientific research, fasting reduces inflammation in your body. It can also minimize the symptoms of chronic diseases caused by inflammation.

Fasting increases the body’s production of antioxidants, which can help with asthma, itchy skin, and fever. So fasting is especially important for people with chronic inflammatory problems.

#3 May enhance heart health

Prolonged fasting increases your ketone levels. It shows that you’re burning body fat and using fatty acids for ketone production. Recent research suggests that increased levels of ketones can regulate your cardiovascular system.

Fasting can also reduce LDL cholesterol and high blood pressure, which can also improve your heart health.

#4 Helps with weight loss

Fasting is an effective strategy for weight loss. When you fast, your body taps into its stored fat as a source of fuel. It means that your body starts relying more on fat breakdown for energy than other energy production processes.

For example, after fasting for 72 hours, the energy released from fat stores becomes about 6 times greater than the energy produced from the liver’s glucose production from amino acids.

This demonstrates that the longer you fast, the more fat your body burns, which helps in weight reduction.

#5 Promotes longevity

Autophagy is a bodily process that recycles and removes damaged or dead cells. It plays a big role in promoting longevity, but the level of autophagy naturally declines as we age.

While autophagy is a natural process that takes place during regular eating, fasting can help. It allows you to restrict your calorie intake, which improves this process. Research shows that up to 30% calorie restriction can improve autophagy-related genes significantly.

Risks and Side Effects of a 5-Day Fast

Along with the benefits, you should know some risks and side effects associated with 5-day fasting. Let’s discuss them in detail.

#1 Muscle atrophy

During a 5-day fast, there is a risk of muscle atrophy, which is the breakdown of muscle tissue. When you don’t eat, your body searches for energy and may start using muscles. Losing muscle mass can slow down your metabolism and increase the likelihood of weight regain after the fast.

Simply put, prolonged fasting can lead to lean muscle mass loss, which can be very harmful to your body. It negatively affects your metabolism and can lead to weight regain. Research shows that you can overcome this challenge by performing physical activity

#2 Fatigue

During a 5-day fast, it’s not uncommon to feel fatigued and experience a decline in energy levels. It usually happens during the initial days, as your body releases a lot of water and salt through urine.

You may experience feelings of weakness, dizziness, and lack of motivation. These effects on your body can also lead to reduced mental performance.

These symptoms occur as your body adjusts to the low calorie intake and the shift from using sugars to burning fats for energy.

You should be aware of these effects as they may affect your energy levels and cognitive performance during the fast. You won’t be able to stay productive, especially if you’re working on tasks that require focus.

#3 Feeling cold

During a prolonged fast of 18 to 24 hours or more, you might feel cold, especially in your hands and feet. This could make you want to wear more layers or use a heater to stay warm.

This happens because fasting activates the part of your nervous system that helps your body rest and digest. Plus, it also reduces your blood pressure, as discussed already.

So, feeling cold during fasting is actually a normal response as your body adjusts to burning fat for energy. It’s a protective mechanism that helps reduce cellular stress and tissue damage.

#4 Risk of health issues

Prolonged fasting can also pose risks to certain individuals with existing health conditions. For example, fasting isn’t recommended for people suffering from diabetes.

That’s because the blood sugar level decreases during fasting, and it can lead to hypoglycemia. It’s an extremely dangerous condition that can result in the worst cases.

People with kidney disease, hypothyroidism, persistent infections, and ulcers should exercise caution. In simple words, if you have any chronic disease, you should seek professional medical advice when considering fasting.

How Often Should You Do a 5-Day Fast?

The frequency of 5-day fasting can vary depending on the individual. Generally, if you have a lean body, you can do a 5-day water fast every 2–3 months. Each fast can make your body stronger and healthier.

For those with a significant amount of weight to lose, fasting once a month can be a suitable option. It’s important to listen to your body and adjust the frequency based on your own needs and health goals.

A recent scientific study has supported the idea of doing a 5-day fast once a month. It shows that it can prevent age-related illnesses like diabetes and cardiovascular disease.

A Word From a Dietitian

Before you begin your fast, you should consult with a healthcare professional. They’ll evaluate your medical history and give you personalized advice based on your needs.

You may experience some effects on your body during the fast, such as fatigue and feeling cold. These reactions are normal as your body adjusts to fasting.

It’s important to gradually reduce your food intake to help your body adapt. You should also drink plenty of water throughout the day to stay hydrated. This will help prevent dehydration and maintain important body functions.

To make fasting more manageable, try activities that help you relax. You can engage in light exercise, such as gentle walking, or practice meditation.

When you break your fast, introduce food back into your body gradually. Start with easy-to-digest foods and add regular meals over a few days. Again, this will help your body adjust properly.

Remember that fasting is a personal journey. This means that what works for one person may not work for you. So listen to your body and know your limits.


What happens after a 5-day fast?

During a 5-day fast, your body will go through many changes. Your digestive system gets a break, allowing it to rest and reset. You may experience weight loss as your body burns stored fat for energy. Lastly, your autophagy process and blood sugar control might also increase.

Is fasting for 5 days healthy?

Fasting for 5 days is healthy for most individuals and offers many benefits. However, it might not be a good option for people who are already suffering from some health conditions.

How to prepare for a 5-day fast?

To prepare for a 5-day fast, it’s recommended to cut back on your food intake gradually. This helps your body adjust to the lower calorie intake.


A 5-day fast can seem challenging, but it’s worth the effort because of the benefits it offers. However, there are risks and side effects to consider, especially for people with existing health problems.

Therefore, it’s important to approach this fasting protocol with caution. Make sure that you listen to your body and consult a healthcare professional if necessary.

If you embark on this journey, don’t forget to follow the tips and techniques discussed in this guide. It can help you maximize the benefit of 5-day fasting and mitigate its risks.

Written by Donika Vata, MD
Dr. Donika Vata is a highly accomplished MD whose extensive experience in the healthcare industry spans over 5 years, making her a distinguished Medical Writer and Researcher for the esteemed Health Reporter. Notably, she also holds the role of a General Practice Doctor and has rendered her exceptional patient care services in various clinics worldwide.
The article was fact checked by Edna Skopljak, MD
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Dr. Donika Vata
Written by Donika Vata, MD
Fact checked by Edna Skopljak, MD
Last update: October 17, 2023
9 min read 840 Views 0 Comments

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