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Home arrow Nutrition arrow Intermittent Fasting arrow What Is Extended Fasting? Benefits and Drawbacks

What Is Extended Fasting? Benefits and Drawbacks

Written by Thalia Oosthuizen
Fact checked by Rosmy Barrios, MD
Last update: October 16, 2023
6 min read 1754 Views 0 Comments
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Long period of time without eating could be beneficial but it has several drawbacks as well. Should you try it? Find the answer in this article.

Extended fasting

With intermittent fasting, you tend to only fast for a short period of time; for example, 8 hours of eating and 16 hours of fasting.

However, there is a thing called extended fasting, where people can fast for upwards of 36 hours. But what is it? Is it safe to fast that long?

Our experts take a deep dive into the world of extended fasting to talk about the safety and risks, the health benefits, and how you can safely participate in an extended fast.

How Long Can You Fast Safely?

For the average person, 36 to 72 hours is the upward limit of fasting safely, though even then, you might start to feel fatigue, headaches, and general hunger discomfort.

Theoretically, the human body can go up to 30 days without food or on limited calories, but that isn’t a safe way to fast. For someone with diabetes, “too long” of a fast could be anywhere from 8 to 16 hours. To be frank, how long you can safely fast is entirely up to your body. 

Whether or not you can safely fast for 24 or 36 hours shouldn’t dictate whether or not you should. Listen to your body, talk to your doctor, and make sure you’re not pushing yourself further than you can handle just because it’s technically safe to do so.

Monk Fast: What Is It?

The monk fast is a take on a type of intermittent fasting called alternate day fasting, in which someone fasts for a 36-hour period once or twice a week. However, with the monk fast, someone drinks nothing but water for 36 hours.

The monk fast is also known as water fasting. There are many people who have championed the monk fast as a way to lose weight, while others have criticized it for being too extreme. With the monk fast, most people only drink water, though you’re also able to drink calorie-free drinks like green tea and black coffee.

While many people who have participated in the monk fast have said that it helps with weight loss results, the downsides could include dizziness, fatigue, nausea, diarrhea and headaches. These side effects are much more prevalent in people who have no history of fasting.

36-Hour Fast – Is It The Same As Monk Fast?

A 36-hour fast is usually completed once or twice a week for those who are looking for the most extreme and rigid end of intermittent fasting. This is the exactly same method as Monk fast.

For those who are taking part in a 36-hour fasting period, it’s usually recommended to start the fast on Monday evening and complete it on Wednesday morning.

It’s important not to dive headfirst into a 36-hour fast without first having some experience prior with intermittent fasting. While you can use this time to do water fasting, it’s also advised to ease into a 36-hour fast with calorie restriction rather than zero calories.

While doing prolonged fasting like this, you also want to make sure you’re drinking water. While on an extended fast, your body will likely start using stored body fat for energy in place of calories, which can cause some minor fatigue as your body gets used to the change.

36-Hour Fast Benefits

While there are some drawbacks to the 36-hour fast, especially if you’re not used to intermittent fasting, there are also a variety of health benefits.

#1 Weight loss

Of course, the majority of people who are committing to prolonged fasting are doing so because of the weight loss benefits. When you restrict your carbs for a long period of time, your body seeks out a new source of energy. With a 36-hour fast, this can encourage your body into the fat-burning state of ketosis.

#2 Heart health

Heart disease kills the most people in the United States every single year. Prolonged fasting could benefit your heart health. Fasting reduces blood pressure, as well as reduces the levels of bad cholesterol in the body. All of these things help reduce your risk of heart disease.

#3 Controls your blood sugar

Another major benefit of fasting is lowering your blood glucose levels and getting control of your blood sugar. Some studies have shown that prolonged fasting has the potential to help increase insulin sensitivity, which can improve insulin levels and reduce your risk of type 2 diabetes.

36-Hour Fast and Autophagy

When you have a particularly long fast length, such as 36 hours, your body can go into a state called autophagy. 

According to the dictionary, autophagy is known as the consumption of the body’s own tissue as a metabolic process occurring in starvation and certain diseases. While that might sound scary, it’s really not.

Autophagy should be looked at as a kind of housekeeping service that your body does. It allows your cells to better adapt to stress, as well as reducing dying or damaged cells, reabsorbing them to make new ones. For many people, 36-hour fasting methods can easily trigger autophagy.

Our bodies go through autophagy regularly, even without fasting. Forms of stress, like vigorous exercise, trigger the process and speed it up. Some studies have shown that our bodies use autophagy to fight off infectious diseases, boost our immune system, and even encourage mental health benefits, like fighting off depression.

When fasting for extended periods, it can trigger autophagy in places in our bodies that need it the most, like the muscles, pancreas, and liver. 

Long-Term Fasting for Weight Loss

Intermittent fasting has been shown to help encourage weight loss. However, experts in both fasting and nutrition agree that taking an extended fast in order to lose a large amount of weight in a short period of time is not particularly effective.

Many people look towards long-term fasting methods as a way to lose bodyweight and burn fat. Extended fasts often promise the benefits of extreme weight loss in a short period of time. However, losing weight is only one benefit of fasting, and long-term fasting for weight loss alone might not be the best method.

The safest way to lose weight is by focusing on a weight loss of 1 to 2 pounds per week. This means that it’s not recommended to lose any more than 4 pounds a week. Extended fasting can help encourage the body to enter into a fat-burning state, but doing so for long periods of time can also be detrimental to your physical health.

Fasting experts agree that while a 36-hour fast has health benefits, it’s important to remember that periodic fasting can also have its downfalls. These fasts work best when done once or twice a month, rather than on a weekly basis.

A Word From Our RD

Humans have been doing periods of fasting for as long as they have been hunting, gathering, and eating. Some spiritual practices even involve an extended period of fasting, some of them anywhere from 48 to 72 hours.

Fasts also often encourage the body’s natural systems: cell regeneration and clean up, the metabolic switch to ketosis, and more. Fasting for a long period of time can even benefit our hearts and brains, so long as we’re doing so under medical advice.

It’s important to remember that fasting, even short-term fasting for just a few hours, isn’t for everybody. While it may be tempting to lose a couple of pounds with a 36-hour fast, you should be talking to your doctor before undertaking something so extreme.

Your health and well-being are far more important than losing a few pounds!


Extended fasting is an eating pattern that requires up to 36 hours as your fasting window. Many people find the fast too extreme, but for those who are well versed with fasting and are looking for the health improvement that comes with extended fasting, it’s a tried and true method.

36-hour fasts can be anything from water fasting to fasting with restricted calories. These types of fasts can encourage the body to trigger a natural cycle called autophagy, in which the body quickly recycles damaged or dying cells and makes them into something new.

While extended fasting can encourage heart health, weight loss, and lower blood sugar, it’s also important to remember that it isn’t safe for everyone to try. If you’re new to fasting entirely, it’s better to stick with shorter 16-hour fasts before you jump into something like extended fasting.

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: October 16, 2023
6 min read 1754 Views 0 Comments

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