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The 5 Day Fast: How To, Risks, and Benefits

By Liam McAuliffe Updated on

The world is brimming with trendy diets and quick fixes for losing weight and boosting overall health and well-being. But fasting is one technique that has been around essentially forever. The 5-day water fast is, for many people, the most potent form of this approach. 

Though seemingly extreme in the context of our “three meals a day plus snacks” dietary culture, a growing body of evidence suggests that short-term water fasting can offer a range of benefits beyond weight loss, including cellular renewal and slowed aging. 

In this article, we’ll explore the 5-day water fast, uncovering its potential benefits, examining potential challenges, and offering a guide to how you can safely undertake a 5 day fast of your own.

Table of Contents

What is the 5 Day Water Fast

health connection watercolor painting illustration hand drawing design symbol

The 5-day fast is a fasting protocol where you abstain from consuming any solid food or caloric beverages for five continuous days. 

The 5-day fast is considered at prolonged fast, which extends beyond the normal intermittent fasting windows that typically range between 12 hours to 36 hours. 

Prolonged fasting regimens have gained attention in recent years for their potential to provide powerful health benefits, including cellular regeneration and renewal, improved insulin sensitivity, and the stimulation of various beneficial hormones and growth factors. 

The 5-day fast is considered an advanced approach that generally requires some preparation and conditioning. It may not be suitable for everyone, especially if you are already underweight, have an eating disorder, or require specific dietary protocols to manage underlying conditions. 

If you have any questions about your readiness to undertake a 5-day fast, it is recommended that you speak to a healthcare professional knowledgeable in fasting protocols. 

Prolonged Fasting Through History

Fasting is as old as humanity. Humans evolved to hunt and feast on large fatty animals, then to fast between successful hunts. In fact, research shows that humans were hypercarnivorous apex predators for nearly 2 million years before the population of large land mammals collapsed under hunting pressure from a growing human population.

With fewer large animals, humans began to cultivate more consistent but dramatically less nutritious plant foods only around 10,000 years ago.

Our modern, industrial food systems and eating habits are an extreme extension of this historically recent and detrimental grain-based agricultural system.

Considering 5 day fasting in this historical light, this modern practice can be viewed as a way to reactivate beneficial metabolic processes that are encoded into our DNA. 

But we don’t have to resurrect fasting from pre-history. Fasting for health has featured in nearly every major civilization, including ancient Egypt, Greece, Rome, and China. 

In ancient Greece, Hippocrates, widely considered the father of Western medicine, advocated for fasting, believing that it allowed the body to heal itself and restore balance.

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What Can I Drink on a 5 day Fast? 

In this article, you may notice that we interchange between” 5-day fast” and “5-day water fast.” Both protocols are the same except for the inclusion of exclusion of noncaloric beverages other than water. 

On a 5 day non-water fast people most often allow unsweetened coffee or black, green, or herbal tea. On a 5-day water fast, you consume only mineral water.

How to Prepare for a 5 day Fast

The best way to prepare for a 5 day fast is to build up to it. Here we’ll outline a step-up approach. 

Graduated Conditioning 

Most people find that 16/8 intermittent fasting, or “Time Restricted Eating” protocol is a sustainable first approach. 

After adapting to these less intense routines for a few days, increase to a twenty-hour fast or an OMAD “One Meal a Day” approach. 

If one meal a day or 20 hours without caloric intake feels good, then move up to a 24 hour fast. Or if you’re feeling well adapted to caloric restriction, then jump straight to a 36 hour fast.  

If you’re comfortable and adapted to a 36 hour fast, it’s likely you’re ready to try a 5-day fast. 

Low-Carb High-Fat Eating

Another way to prepare your body for a 5 day fast is to practice a low-carb high-fat diet like keto or carnivore

Cutting carbs and focusing on nourishing fatty whole foods, especially meat, will train your body to efficiently metabolize fat for energy. This process, called ketosis, is a metabolic state that your body enters when you do a prolonged fast. Adapting to ketosis before a fast reduces the challenges of transitioning into a fasted state. 

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Avoid Processed Foods, Focus on Whole Foods

When gearing up for a prolonged 5 day water fast, it’s important to nourish your body with nutrient-dense whole foods. During a fast your body will rely on stored macro and micronutrients.

Foods to help you get nutritionally-replete before fasting include

Nutrient Dense Foods list


While focusing on these whole foods, it’s important to avoid processed foods high in toxic vegetable oils, added sugars, and refined grains. All of these industrial products cause inflammation, distort hunger/satiation hormones, and imbalance blood sugar. 

What are the Health Benefits of a 5 Day Fast? 

Most people have a intuitive sense that intentionally abstaining from food for periods of time can be physically rejuvenating, but few people actually know why and how fasting can benefit your health. So let’s take this opportunity to get into some of the science behind these health benefits. 

Autophagy and Cellular Regeneration

One of the most powerful benefits of fasting is that it stimulates a natural process of cellular regeneration and renewal called autophagy.

Think of autophagy as a natural detoxification process. On a cellular level, your body removes damaged cell parts and recycles the raw materials into new high-functioning cell parts. 

The resulting cellular regeneration has been linked to numerous health benefits, including increased longevity and reduced risk of various diseases.

On the other hand, interrupting autophagy with constant caloric intake can lead to diseases including diabetes, cancer, and infectious and neurological diseases. 

diagram of autophagy

Hormonal Balance Leading to Weight Loss

A 5 day water fast can significantly reduce insulin levels, allowing your body to become more sensitive to its effects. 

Improving insulin sensitivity regulates blood sugar and allows your body to efficiently metabolize stored fat.

The 5 day fast also increases leptin sensitivity. Leptin is another hormone associated with food cravings and weight gain and loss.

When you eat constantly, your brain becomes resistant to leptin signaling. And since leptin is responsible for telling your body that you’ve had enough to eat, being leptin resistant can cause a cycle where you crave and consume more food than your body needs, store excess fat, and lack the motivation to move your body.

Resensitizing and rebalancing insulin and leptin can aid in weight loss, while reversing type 2 diabetes and supporting cardiovascular health, cognitive ability, and fertility. 

diagram of leptin resistance cycle

Mental Clarity, Focus, and Cognitive Health

Fasting is a powerful way to boost mental clarity, focus, and improve overall cognitive health while defending against neurodegenerative disease.

The 5 day fast can support cognitive ability and preserve cognitive health in various ways, including

  • Reducing excess weight, thereby increasing blood flow to the brain
  • Activating neuropathways that promote the growth and maintenance of brain cells
  • Stimulating autophagy that renews and repairs brain cells
  • Reducing inflammation
  • Protecting the brain from elevated blood sugar
  • Feeding your brain cells with ketones–a superior energy molecule created from fat 

diagram of effects of fasting on brain health

Resetting Eating Patterns and Freedom from Food Cravings

handcuffed to donut

Embarking on a 5-day water fast can serve as a powerful reset for unhealthy eating patterns and food cravings. By abstaining from solid food for an extended period, individuals can break free from the cycle of emotional eating, mindless snacking, and processed food dependency. This newfound awareness and control over eating habits can lay the foundation for a healthier relationship with food moving forward.

Potential Challenges and Considerations

If you’re compelled to give the 5 day fast a try, it’s also important to be aware of any risks and how to avoid them. 

During this extended fast, most people will feel periods of hunger, fatigue, and temporary physical discomfort. 

Use extra caution and consult with a healthcare professional knowledgeable in fasting if you have serious underlying health conditions. 

This intensive fasting approach is not appropriate for women who are pregnant or breastfeeding, or for people who have a history of disordered eating. 

Consulting a healthcare professional and monitoring your body’s response throughout the process is crucial for a safe and successful fast.

Risks to Watch For

  • Nutritional Deficiencies: load up on fatty, whole foods before and nourish your regenerating cells with these same animal-based superfoods afterward. 
  • Electrolyte Imbalances: make sure you’re getting enough electrolytes, including sodium, potassium, and magnesium. Monitor for irregular heartbeat, dizziness, and fatigue.
  • Dehydration: when water fasting, make sure you are drinking mineralized water and add electrolytes when necessary. 

The 5 Day Fast: The Takeaway

The 5-day water can be a transformative experience with benefits that extend far beyond mere weight loss. 

By tapping into your body’s innate healing mechanisms, such as autophagy, stimulation of neuroprotective hormones, improved insulin sensitivity, and a reorientation to eating patterns,  the 5 day fast holds the potential for overall enhancement of wellbeing. 

However, it is important for most people to work up to such an intensive approach, beginning with shorter intermittent fasting protocols and practicing low-carb eating beforehand. 

Overall, the 5 day water fast can be a profound doorway into self-discovery, physical and mental rejuvenation, and a renewed sense that you have control over your well-being.

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