What Is 72 Hour Fast?

What Is 72 Hour Fast?

Written by Andrew Brewer. ⚕️Reviewed and fact checked by our medical team.

What Is 72 Hour Fast?Intermittent fasting is a great way for you to readjust your relationship with eating, viewing it as a way to fuel your body’s important processes. Of course, you can find enjoyment in eating, but Intermittent fasting teaches you that there is a time and a place for eating. Prolonged fasts like 48-hour or 72-hour fasts take that up a level.

Instead of eating each day, during a 72-hour fast, you will refrain from eating for three days. This will force your body to break down the fat stores that are already in your body, promoting weight loss, among other fantastic benefits.

The longer you fast, the more benefits you will trigger in your body. A 72-hour fast may seem intimidating, but once you get used to it, you will start to recognize the many benefits.

Key Takeaways

  • Intermittent fasting, including prolonged fasts like a 72-hour fast, can help readjust your relationship with eating and view it as a way to fuel your body’s important processes.
  • A 72-hour fast involves refraining from eating for three days, which forces the body to break down fat stores, leading to weight loss and other benefits.
  • During a 72-hour fast, the body enters ketosis after 12 hours without eating, using fat stores to produce ketones for energy and promoting weight loss.
  • 72-hour fasting triggers autophagy, a process where the body replaces dead and damaged cells with new ones, reducing the risk of diseases like cancer.
  • While a 72-hour fast can have benefits, it may cause side effects such as hunger, dizziness, brain fog, and confusion. It is important to consult a doctor, especially if you have pre-existing health conditions, before attempting prolonged fasts. Gradually building up to a 72-hour fast over time is recommended for optimal results.

72-hour Fasting and Weight Loss

One of the biggest reasons that people start a 72-hour fast is to lose weight – and with good reason. After 12 hours without eating, your body enters ketosis. This means there are no more calories to burn, so your body starts to turn its fat stores into ketones, which can be used for energy.

Simply put a 72-hour fast forces your body to burn its fat to keep the critical processes going. As a result, you will lose weight. Typically, you will lose a few pounds, but don’t be discouraged if you don’t see the needle move too much. You may notice your clothes are feeling looser or your face is looking slimmer. These still count as weight loss.

72-hour Fasting and Autophagy

In addition to weight loss, 72-hour fasting also triggers autophagy in the body. While that may sound intimidating, it is simply the process of the cells in your body replacing dead and damaged cells with new ones. As a result, you will reduce the risk of developing diseases, including cancer.

It may vary slightly from person to person, but typically, you will enter into autophagy after fasting for 18 hours. You can be both in ketosis and autophagy at the same time; however, you do not have to be in one to achieve the other.

Are There Side Effects to a 72-hour Fast?

Aside from hunger, there are several side effects that you may face during your 72-hour fast. These are normal, but if you have any concerns, you can see a doctor. Some people, especially those with pre-existing health conditions, should not undergo intermittent fasting, especially prolonged fasts, without supervision.

Some people report being dizzy and lightheaded during a 72-hour fast. Additionally, they may suffer from brain fog, confusion, and disorientation. These will pass after you eat, but make sure to stay hydrated and drink a lot of water to prevent getting dehydrated.

The benefits of a 72-hour intermittent fast far outweigh the positives, causing your body to rest and recover in ways that it could not if you were constantly feeding it.

You should not start with a 72-hour fast if you are new to intermittent fasting. Instead, train yourself over the course of months to be able to tolerate this for the best results.

Is a 72-hour Fast Good for You?

Yes, a 72-hour fast can be good for you, though some individuals may not react well to it if they have underlying medical conditions. Your body enters into autophagy and ketosis, helping you burn fat and feel good while doing it.

Ultimately, it’s your choice to undergo a prolonged fast, and if you can make it through three days without food, you will look and feel better, which is a reward unto itself!


  • What is a 72-hour fast?

A 72-hour fast involves abstaining from eating for a period of three consecutive days, forcing the body to rely on its fat stores for energy.

  • How does a 72-hour fast promote weight loss?

During a 72-hour fast, the body enters a state of ketosis after approximately 12 hours without food. In ketosis, the body burns stored fat to produce ketones, which can be used as an energy source, leading to weight loss.

  • What is autophagy, and how does it relate to a 72-hour fast?

Autophagy is a natural cellular process where damaged and dead cells are cleared out and replaced with new ones. A 72-hour fast triggers autophagy, which can have various health benefits, including reducing the risk of diseases like cancer.

  • Are there any side effects of a 72-hour fast?

While a 72-hour fast can have positive effects, there may be some side effects. Common side effects include hunger, dizziness, brain fog, and confusion. It is important to stay hydrated and consult a doctor, especially if you have underlying health conditions, before attempting prolonged fasts.

  • Can anyone do a 72-hour fast?

While a 72-hour fast can be beneficial for many individuals, it may not be suitable for everyone. People with pre-existing health conditions or those new to intermittent fasting should exercise caution and seek medical advice before attempting prolonged fasts. It is recommended to gradually build up fasting tolerance over time for optimal results.

  • How do I prepare for a 72-hour fast?

If you are new to intermittent fasting, it is advisable to start with shorter fasting periods and gradually increase the duration over several months. This allows your body to adapt and reduces the risk of experiencing severe side effects. Additionally, staying hydrated, consuming a balanced diet before and after the fast, and consulting a healthcare professional can help you prepare effectively.

  • Can I exercise during a 72-hour fast?

Engaging in light to moderate exercise during a 72-hour fast is generally safe and can even enhance the fat-burning process. However, listen to your body and avoid strenuous workouts that may cause excessive fatigue or dizziness. It is recommended to consult a healthcare professional or a fitness expert for personalized guidance.

  • Will I regain the weight lost after a 72-hour fast?

Weight regain after a 72-hour fast can occur if you resume unhealthy eating habits or consume excess calories. It is important to transition back to a balanced diet gradually and maintain a healthy lifestyle to sustain weight loss in the long term.

  • Can I consume any fluids during a 72-hour fast?

Yes, staying hydrated is crucial during a fast. You can drink water, herbal tea, black coffee, or other non-caloric beverages to support hydration. However, it is best to avoid sugary drinks or those with added calories to ensure the fast’s effectiveness.

  • Are there any specific guidelines to follow after completing a 72-hour fast?

After a 72-hour fast, it is advisable to break the fast with a light meal and gradually reintroduce regular, healthy foods to avoid digestive discomfort. Prioritize nutrient-dense foods and listen to your body’s hunger and fullness cues. If you have any concerns or questions, consulting a healthcare professional is recommended.

Andrew Brewer

Andrew Brewer

Andrew Brewer started Fastingapps.com to give people the guidance that he never received when he was first starting. His goal is to make your goals achievable and to offer you only the best fasting apps that the internet has to offer. You're not on your own - Andrew and the entire family of reviewers at Fastingapps.com are here with you every step of the way!