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Home Fasting Extended Fasting: How To Fast Safely?

Extended Fasting: How To Fast Safely?

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Intermittent fasting has gained traction as an effective tool for weight loss in recent years. Numerous studies have found it a good tool for healthy weight loss that comes with many other health benefits.

Extended fasting, or prolonged fasting, falls within the intermittent fasting style of eating but is characterized by much longer periods of fasting. Fasting methods like the 36-hour fast fall into this category.

Prolonged or extended fasting is thought to increase weight loss as well as the other benefits of fasting, but what exactly does it entail, and is it safe for everyone?

In this article, we’re going to take a look at prolonged fasting, how it works, how it benefits the body, and how it can help you on your weight loss journey. Take a look below to find out more.

Extended Fasting – What Is It?

Extended fasting is a style of intermittent fasting in which you engage in extended fasting periods. Usually, a fast will last for 36 hours or more. During this time, you cannot consume any calories and must only drink water and unsweetened, zero-calorie beverages.

Intermittent fasting gained popularity for its effectiveness in weight management. By restricting the time you can eat, you’re effectively creating a natural calorie restriction and deficit across the day. A calorie deficit is where you burn more calories than you consume each day and is known to be an effective method of weight loss.

You can create a deficit by eating fewer calories but also by burning more calories during the day. You can burn more calories by incorporating a daily walk, a long-distance run, or even a pilates class into your routine.

Extended fasting also causes a metabolic switch in the body into the state of ketosis. When you fast for a long period of time, your blood glucose levels drop, meaning your body needs to find another source of fuel. Ketosis usually sets in around 12 hours into a fast and is where your body burns stored body fat for fuel in place of blood sugar.

The longer you fast, the longer your body remains in this state, and therefore, the more body fat stores that are burned to fuel the body. This helps with overall weight reduction and can help to boost health too.

If you’re considering starting a form of prolonged fasting, you could benefit from using the DoFasting app. The app provides a space for you to track your caloric intake, water intake, and weight loss progression as you embark on your extended fasting regime.

It offers a whole variety of fasting-friendly recipes, workouts, and tips and tricks for staying motivated while fasting. The app also has a handy alarm system that reminds you when to start fasting and when to stop.

Benefits of Extended Fasting

Prolonged fasting is thought to have many benefits for your health, including weight loss, better blood pressure control, and mental health benefits. We’ve summarized some of the top benefits of extended fasting below for you to check out.

#1 Weight loss

The number one reason people begin prolonged fasting regimes is to lose weight, and this kind of fasting has been shown to induce significant weight loss in individuals. The weight reduction mechanisms of extended fasting are threefold.

Firstly, extended fasting periods create a calorie deficit by reducing the amount of time you have to eat. Time-restricted eating is a well-known method of weight reduction and is featured in intermittent fasting styles like the 12-hour fast and the 16:8 method.

Fasting also causes a metabolic shift to the state of ketosis. This is the fat-burning state induced by fasting (and by the ketogenic diet), where the body uses fat stores for fuel. It is a natural state in the human body and offers survival when blood sugar stores are depleted.

Lastly, fasting may boost metabolism. Your metabolism is the process of your body turning the calories you consume into energy. A faster metabolism means burning calories quicker which may promote weight reduction.

#2 Better blood pressure management

Research suggests that fasting decreases BP levels in hypertensive and non-hypertensive patients when undertaken long-term, and fasting, in general, is known to lower BP and a range of other biomarkers of poor cardiovascular health.

While prolonged fasting may have a positive effect on BP, it is important to note that there are other ways to reduce hypertension. These include getting more exercise, perhaps by running daily or engaging in jump rope, and by decreasing sodium intake.

#3 Mental clarity

It has been suggested that prolonged fasting periods can boost mental performance, cognitive function, and mental clarity. Furthermore, there is some research to suggest that fasting could have a positive effect on mental health conditions, like anxiety, stress, and depression.

As fasting is not a cure-all, you should speak with a mental health professional if you are concerned about your anxiety, stress, or depression levels.

In addition, you can manage these conditions in other ways, like engaging in stress-reduction methods, like meditation and mindfulness, and getting more physical activity and fresh air, perhaps by walking a few miles each day.

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#4 Reduced inflammation

Fasting is well-known for its anti-inflammatory effects and is known to reduce both chronic inflammation and oxidative stress. Both of these have been linked with a number of chronic conditions, including arthritis, cancer, diabetes, and allergies. Fasting may help reduce the risk of developing some of these conditions.

#5 Improved insulin sensitivity

Prolonged fasting means lowering blood sugar levels and insulin levels for long periods of time. This can help boost insulin sensitivity and improve blood sugar control. Both of these factors can help reduce the risk of developing prediabetes and type 2 diabetes later in life.

If you already have prediabetes or type 2 diabetes, it is important you speak with your doctor before embarking on a prolonged fasting regime as a way to manage your condition. Indeed, it may even be safer to start with a less-challenging form of fasting, like the 12-hour method, before trying a longer fasting period.

Extended Fasting for Weight Loss – Is It Effective?

Prolonged fasting is thought to be an effective method of weight reduction. It is particularly useful for those who have engaged in unhealthy eating habits as it forces a natural calorie restriction but still allows you to eat what you want to.

Prolonged fasting also induces a state of ketosis. This can help alter body composition and reduce body fat, helping to support weight reduction overall.

While prolonged fasting is thought to be an effective tool for losing weight, it is important to continue to eat a healthy and balanced diet during your eating periods. This means consuming whole grains, fruits and vegetables, healthy fats, and protein and avoiding processed and refined foods.

You can increase your weight reduction efforts during a fasting period by exercising more. However, during prolonged fasting periods, it is best to exercise at a low intensity and keep hydrated so as not to exhaust yourself.

Tips on How to Get Started on Extended Fasting

When starting out with prolonged fasting, it is a good idea to try other fasting methods. You could start out with a less challenging method, like the 14:10 fasting method, to introduce your body to fasting.

As you gradually get used to this style and stop experiencing fasting side effects, like headaches, you can then move on to longer fasts, like the 20:4 method or even the OMAD style.

To get your body prepared for zero-calorie diets, you could also eat at a reduced calorie rate a few times a week. IF styles, like the 5:2 method, offer a structured way of trying this style out. In this method, you eat at a reduced calorie rate for 2 out of 7 days a week.

Once you have mastered this style, you can begin trying longer fasts. You could start with a 24-hour fast or a 36-hour fast and then move on to longer periodic fasting. It is very important, as you begin prolonged fasting, that you listen to your body. If you begin to feel weak or dizzy, then you must stop fasting immediately.

During long fasting periods, it is incredibly important that you stay hydrated by consuming zero-calorie drinks like green tea. You may also be able to curb some side effects, like hunger pangs, by taking a fiber supplement or appetite suppressant.

Always speak with a doctor or health professional before undertaking an extended period of fasting.

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Is Extended Fasting Safe? 

Extended fasting can be done safely, but it is a riskier method of losing weight and should be practiced with caution. Indeed, if you are planning on trying it out, you might want to speak with a doctor or nutritionist for tips on the safest method of prolonged fasting.

During a prolonged fast, it is imperative that you remain hydrated, either through drinking only water if you’re trying a strict water fasting method or through both water and other zero-calorie drinks. Indeed, you may even want to allow some calories, like in the 5:2 method, wherein you can eat 500 calories as a female and 600 calories as a male.

You may also want to try taking an appetite suppressant or fiber complex to reduce hunger pangs and cravings and should ensure you break the fast properly and safely.

There are some people who should never try a prolonged fasting regime, and these include:

  • Anyone with a history of eating disorders – prolonged fasting can promote disordered patterns of eating and could even lead to the development of an eating disorder.
  • Pregnant and breastfeeding people
  • Anyone with a chronic condition that would be exacerbated by an extended fast
  • Anyone under the age of 18
  • People with sleeping problems
  • People who need to take certain medications with food

How to Break an Extended Fast Safely

Breaking your fast safely is important to ensure you don’t promote weight gain or develop digestive issues. It is important to start out with soft, easy-to-digest food before working your way back up to your normal food intake.

Some goods foods to break an extended fast include:

  • Smoothies
  • Dried fruit
  • Soups
  • Fermented foods
  • Bone broth
  • Healthy fats

After you have reintroduced your digestive system to softer foods, you can begin introducing more complex foods. It is important that you do not exceed a normal calorie intake after an extended fast, as you may negate all of the health benefits of fasting for weight reduction.

You should also never break an extended fast with processed, refined, or sugary foods. These foods are very high in sugar and may cause a blood sugar spike that results in a crash. This can have a negative impact on insulin levels and could be dangerous for your health.

The key to breaking an extended fast is to do it slowly and with only the most nourishing foods.

A Word From Our Nutritionist

Extended fasting is an effective method of reducing body weight and pushing your body to burn fat. It has a number of health benefits, including promoting heart health, better blood sugar control, and weight management, as well as increased autophagy and reduced inflammation.

Prolonged fasting may be a good option for people who have struggled with other dieting methods. This is because an extended fast forces a caloric restriction without telling you what you can and cannot eat. So, you can still eat your favorite foods, just in your allotted feeding hours.

It could be a good idea for those prone to emotional eating or those who have formed an unhealthy eating pattern over the years.

That being said, the most successful fasters are the ones who eat whole and healthy foods during their eating window to enhance their weight reduction efforts.

Extended fasts are a riskier method of dieting. Indeed, they can result in low BP, lower blood sugar, and other side effects like hunger pangs, dizziness, and headaches. This is why it is imperative you undertake extended fasts in the safest possible way.

This means staying hydrated, balancing electrolytes, and using appetite suppressants to manage side effects. You may also consider consuming a few hundred calories each day to make long-term fasting easier.

Good IF methods to try out to prepare you for prolonged fasting include the alternate day fasting method, the 5:2 method, and the 36-hour fast.


Prolonged fasting is thought to be an effective method of weight and fat reduction but is considered a riskier style of dieting. It can be done safely, provided you listen to your body, stay hydrated, and stop if you feel unwell.

If you’re considering a prolonged fast but don’t know where to start, the DoFasting app is available to offer tips and tricks on a range of dieting methods and even provides a space for you to track your progress.

Written by
Edibel Quintero, MD

Edibel Quintero is a medical doctor who graduated in 2013 from the University of Zulia and has been working in her profession since then. She specializes in obesity and nutrition, physical rehabilitation, sports massage and post-operative rehabilitation. Edibel's goal is to help people live healthier lives by educating them about food, exercise, mental wellness and other lifestyle choices that can improve their quality of life.

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