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Home arrow Nutrition arrow Intermittent Fasting arrow 72-Hour Fast: The Benefits and Risks You Must Know

72-Hour Fast: The Benefits and Risks You Must Know

Written by Thalia Oosthuizen
Fact checked by Rosmy Barrios, MD
Last update: January 16, 2024
3 min read 2869 Views 0 Comments
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Every fasting regimen has a lot of health benefits and 72-hour fast is no exception

72 hour fast benefits

Fasting for 72 hours is an amazing feat that many dedicated to the intermittent fasting lifestyle take on. The challenge of fasting for that long is often outweighed by the health benefits.

Our fasting experts have taken the time to outline and detail the benefits of this fast, as well as take a look at some of the risks.

What Is 72-Hour Fasting?

A 72-hour fast is often also called a water fast. Water fasting is when someone does prolonged fasting without drinking anything other than water. No black coffee, no green tea, not even flavored water.

Some people fast by greatly reducing calories rather than not eating at all. But water fasting relies on no solid food, just water.

How Long Can You Fast Without Food?

When it comes to intermittent fasting, 72 hours is the limit of what anyone should fast without food. If for any reason you’re to go more than that limit, you must do so under medical supervision and with your doctor’s approval.

How long the human body can go without food is often tempered by how long the human body should go without food.

Our ancestors often spent days searching for food through hunting and gathering. Our bodies are designed to be able to survive 30 days without food. However, doing that can cause a whole host of health risks.

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7 Amazing Benefits of a 72-Hour Fast

There are a plethora of benefits of a 72-hour fast, but let’s take a look at some of the best.

#1 Cell regeneration

Our bodies need to rest and regenerate, including our cells. Fasting allows our bodies to focus on regenerating new immune cells rather than spending energy elsewhere.

#2 Autophagy

Autophagy is a process in which the body breaks down damaged or dying immune cells and reuses them. It’s like a natural form of recycling [1].

#3 Blood sugar levels decrease

Extended fasting can be wonderful for people who are at risk of type 2 diabetes due to the lowering of blood glucose levels.

#4 Heart health benefits

When you take time to fast, it can help lower your blood pressure. This can help reduce the risk of heart disease.

#5 Weight loss

Weight loss is one of the top reasons people do intermittent fasting. A fast that lasts 72 hours encourages the body to enter fat-burning mode and promotes weight loss.

Studies also show that extended fasting also may help you maintain muscle mass [2].

#6 Reduces inflammation

Chronic inflammation can cause all kinds of risks to the body, including cancer cells. However, fasting can reduce inflammation and reduce your risk of chronic diseases.

#7 Boosts the immune system

Finally, it has been noted that people who fast tend to stay healthier for longer and don’t get sick during the winter. This is because fasting encourages the body to boost the immune response.

Studies have shown that extended fasting also has a big impact on human growth hormone (HGH) secretion. HGH plays an important role in cell repair and metabolism [3]. 

Potential Risks of the 72-Hour Fast

While there are health benefits to fasting, such a long fast is not without risks. It’s important to go in knowing exactly what you’re getting into. 

Let’s go over some of the risks of water fast.

#1 Hypertension

While lowered blood pressure is a benefit, there are some people who go the opposite way. Hypertension is a concern with longer fasts, so keep an eye on your blood pressure [4].

#2 Dehydration

If you don’t drink enough water while you’re water fasting, you’ll end up incredibly dehydrated. Most people aren’t aware of just how much water they need in a day, so keep track of your water intake. 

#3 Dizziness and fatigue

If your metabolism isn’t used to using body fat as a form of energy, you’re likely going to feel dizzy and fatigued. If this happens, make sure to break your fast and talk to your doctor.

Try drinking bone broth while fasting, as it helps to keep you energized, especially if you are fasting for more than 36 hours.

#4 Eating disorders

And finally, a fast could possibly trigger eating disorders in some people. Make sure to talk to your doctor and be aware of your own mental clarity before attempting a fast.

A Word From Nutritionist

Going from a normal diet to fasting can be difficult for even the healthiest of people. It’s essential that you’re aware of any health conditions that could make fasting dangerous for you and stay in touch with your healthcare provider.

Before you cut out solid foods, make sure you have a good history of fasting to begin with; otherwise, the metabolic switch can be hard. Start with fasting for a few hours, then work up to alternate-day fasting.

Make sure your last meal is low in carbs and high in healthy fats. This will help encourage a state called ketosis and make it easier for you to make it through your fast. It’s also recommended to start with a low-calorie diet a few days beforehand.


The 72-hour fast has great benefits. From improving insulin levels to fat loss, whatever your reason for fasting, you’ll be sure to find it. An extended fast can help with cancer prevention, as well as reduce the risk of chronic disease.

However, it’s important to stay vigilant. Water fasting can also cause issues if you’re not prepared. Dizziness, dehydration, and eating disorders are risks for people who choose to take on a fasting challenge.


  1. Glick D, Barth S, Macleod KF. Autophagy: cellular and molecular mechanisms. J Pathol. 2010 May.
  2. Williamson E., Moore DR. A Muscle-Centric Perspective on Intermittent Fasting: A Suboptimal Dietary Strategy for Supporting Muscle Protein Remodeling and Muscle Mass? 2021.
  3. Moller L., Dalman L., Norrelund H., Billestrup N., Frystyk J., Moller N., Lunde Jorgensen JO. Impact of Fasting on Growth Hormone Signaling and Action in Muscle and Fat, The Journal of Clinical Endocrinology & Metabolism, Volume 94, Issue 3, 1 March 2009, Pages 965–972,
  4. Gonzalez JE, Cooke WH. Influence of an acute fast on ambulatory blood pressure and autonomic cardiovascular control. 2022 May.
Written by Thalia Oosthuizen
Thalia has always wanted to be a writer, starting her first local newspaper at the age of 11. She also has enjoyed a passion for health and fitness since a young age, playing many sports through her schooling career, and still enjoys biking, running, and swimming today. She studied English Language at University for 3 years, developing a passion for spelling, grammar, and research. She now has over 10 years of experience writing, proofreading, and editing, and has paired this with her love for health and fitness by writing health content.
The article was fact checked by Rosmy Barrios, MD
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Written by Thalia Oosthuizen
Fact checked by Rosmy Barrios, MD
Last update: January 16, 2024
3 min read 2869 Views 0 Comments

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