36-Hour Fast: Benefits and Risks, Is it Effective for Weight Loss?

What Is a 36-Hour Fast or Monk Fast?

A 36-hour fast, aka monk fast, is a type of intermittent fasting where you need to avoid consuming calories for a consecutive 36 hours to reach health benefits [1].

You must avoid calories during the fasting period, i.e., you can’t eat solid foods, liquids with calories, and sugary drinks. The only things you can consume during fasting are non-caloric drinks like water, herbal tea, and black coffee to stay hydrated and suppress hunger. If needed, you can consume electrolytes to steer clear of dehydration.

You can plan the 36-hour fasting based on your routine. For example, you can fast from dinner on one day to breakfast on the following day.

Studies show that avoiding food for an extended period can lead to weight loss through various processes in the body.

Learn More: 18-Hour Fast Diet: Benefits and Weight Loss Results

Is a 36-Hour Fast Good for Weight Loss?

Yes, a 36-hour fast can boost weight loss because of the following processes that appear during this extended fasting period.

• Caloric Deficit: Consuming fewer or no calories can simply lead the body to use stored fat to provide energy, which means fat burn and weight loss [2].
• Fat Burning: During fasting, when glycogen stores are emptied so the body can provide the energy needed for various bodily functions, the body begins to burn fat instead of carbohydrates, which leads to weight loss [3].
• Insulin Sensitivity: Fasting can improve insulin sensitivity, meaning that the body can better control blood sugar levels and doesn't need to produce as much insulin to manage blood sugar, which helps prevent the storage of excess glucose as fat [4].
• Reduced Fat Storage: High insulin levels promote fat storage and interfere with the breakdown of fat for energy. By improving insulin sensitivity, your body can lower insulin levels, which facilitates the breakdown of stored fat (lipolysis) and reduces the creation of new fat cells [5].
• Decreased Hunger and Cravings: Improved insulin sensitivity can stabilize blood sugar levels, reducing sudden spikes and drops that lead to hunger and cravings, which can help you control your appetite and reduce overeating [6].
• Lower Inflammation: Insulin resistance is often associated with chronic inflammation, which can interfere with weight loss. By improving insulin sensitivity, you can reduce inflammation, which can help your body respond better to weight loss efforts [7].
• Appetite Regulation: Fasting can trigger hunger hormones like ghrelin and reduce appetite, which means less calorie intake during eating windows and better weight control [8].

Also, if you have followed low-carb diets you may have heard of a fat-burning state called ketosis, which results from cutting carbohydrates. This state can also be achieved with a 36-hour fast.

Learn More: What Is Fat Fasting? Side Effects, Meal Plan, and Food List

Will a 36-Hour Fast Put Me in Ketosis?

Yes, a 36-hour fast can put your body into ketosis, where the body uses ketones as an energy source instead of glucose from carbohydrates.

As you consume lower (almost zero) calories from carbohydrates during fasting, your body can enter ketosis and burn excess fat stored in your body.

So, how much weight can we lose on a 36-hour fast?

How Much Weight Can You Lose on a 36-Hour Fast?

The first important point to note about weight loss on a 36-hour fast is that the first weight you lose on intermittent fasting is probably water weight, not fat.

It will take some time for the body to enter ketosis and start burning fat. Although water weight loss is also weight loss, it can be returned by eating food or drinks.

The amount of weight you can lose on a 36-hour fast depends on various personal factors like your initial weight and metabolic function and there’s no one-size-fits-all answer.

Anyhow, you might lose 1-3 pounds of water weight, depending on how much glycogen your body has stored. Actual fat loss during a 36-hour fast can be around 0.25-0.5 pounds since burning a pound of fat requires a deficit of about 3,500 calories, which is more than most people burn in 36 hours.

But if you do not notice weight loss after a 36-hour fast, it may be because of one or some of the following scenarios.

Why Am I Not Losing Weight on My 36-Hour Fast?

• Water Retention: Your body may be retaining water due to various factors such as salt intake, hormonal changes, or stress, which can mask fat loss on the scale.
• Metabolic Adaptation: Your metabolism might slow down in response to fasting, reducing the number of calories you burn, which is a natural survival mechanism that conserves energy during periods of low food intake.
• Overcompensation After Fasting: If you eat significantly more than usual before or after your fast, you might offset the caloric deficit created during a 36-hour fast. Overeating in response to hunger or a sense of reward can negate the benefits of fasting.
• Muscle Loss: Extended fasting can lead to muscle loss, lowering your metabolic rate. Less muscle mass means fewer calories burned at rest, making weight loss more challenging.
• Hormonal Factors: Hormones like cortisol (the stress hormone) and insulin can affect weight loss. High cortisol levels can lead to weight retention, especially around the belly. Insulin sensitivity is also important in how your body stores and uses fat.
• Inaccurate Caloric Intake and Output: Misjudging the number of calories consumed before or after fasting, or overestimating the number of calories burned through exercise, can impact weight loss.
• Body Composition Changes: Sometimes, the scale doesn't reflect fat loss accurately. You might be losing fat but gaining muscle, which can result in no significant change in weight.

The good news, however, is that weight loss is not the only benefit you can get from extended intermittent fasting like a 36-hour fast, and there can be many health benefits.

Learn More: Can You Chew Gum While Fasting? 10 Best Gums for Fasting

The Benefits of a 36-Hour Fast

• Improved Insulin Sensitivity
• Cellular Repair through Autophagy
• Brain Health and Mental Clarity
• Anti-Inflammatory Effects
• Metabolic Benefits for Type 2 Diabetes

Improved Insulin Sensitivity

Intermittent fasting, including a 36-hour fast, can increase insulin sensitivity and lower the risk of type 2 diabetes. A 2005 study reported that intermittent fasting had a positive effect on insulin sensitivity and reduced insulin levels in participants with insulin resistance [9].

Cellular Repair through Autophagy

A 2007 study showed that fasting activates autophagy, a cell-level process to remove damaged cells and improve cellular health and longevity [10].

Brain Health and Mental Clarity

During extended fasting, when the body is not involved with processing food, it focuses on repairing and optimizing cellular function, which can result in mental clarity.

Also, a 2021 study analyzing various clinical studies indicated that intermittent fasting could lead to anatomical and functional changes in the brain through various processes, including producing brain-derived neurotrophic factor (BDNF), a protein for neuron growth and cognitive function.

These changes can help improve epilepsy, Alzheimer’s disease, multiple sclerosis, Parkinson’s disease, ischemic stroke, autism spectrum disorder, mood, and anxiety disorders [11] [12].

Anti-Inflammatory Effects

Chronic inflammation can lead to various diseases, including cardiovascular, neurodegenerative, autoimmune, respiratory, and diseases, metabolic and digestive disorders, cancer, and skin conditions.

A 2014 study on the effects of intermittent fasting on neuroinflammation and memory impairment found that intermittent fasting can decrease oxidative stress and inflammation [13].

Metabolic Benefits for Type 2 Diabetes

Various studies indicate a positive correlation between intermittent fasting and treating type 2 diabetes. Fasting can improve insulin sensitivity, which helps reduce the risk of type 2 diabetes. It can also promote cellular repair and improve metabolism [14].

Despite these positive health effects, a 36-hour fast can include some side effects, especially in those new to extended fasting and individuals with underlying health concerns.

Learn More: The 60-Hour Fast Benefits and Results: Is It Safe?

The Side Effects of 36-Hour Fast

• Dehydration
• Headache and Dizziness
• Fatigue and Weakness
• Hunger and Cravings
• Mood Changes
• Digestive Issues

Dehydration

Prolonged fasting decreases satiety, which may stop you from drinking enough water and cause dehydration. A 1982 study published in the Journal of Clinical Endocrinology and Metabolism reported that fasting for 36 hours without fluid intake resulted in significant water loss and dehydration.

To avoid dehydration, you can drink enough water, electrolyte drinks, and other non-caloric beverages during fasting hours [15].

Headache and Dizziness

A 2023 study on intermittent fasting over 1 to 3 months on male and female participants ranging from 18-35 years old found that avoiding food for an extended period like in a 36-hour fast can lead to headaches and dizziness [16].

Fatigue and Weakness

Various studies have indicated that not receiving enough calories daily like during extended intermittent fasting can cause lethargy, fatigue, and weakness [17].

It’s necessary to monitor your symptoms and break the fast in case of serious fatigue, headache, or similar side effects.

Hunger and Cravings

It’s no secret that hunger and cravings are among the most common side effects of intermittent fasting. Various studies have confirmed these side effects.

For example, a 2018 study on 112 men and women found that although intermittent fasting can lead to weight loss, it can cause hunger and cravings [18].

Another 2019 observational study on 1422 participants over 12 months found that although adverse effects were observed in less than 1% of the population, the participants showed hunger symptoms during the early days of fasting [19].

Mood Changes

A 2016 study on the psychological effects of intermittent fasting on women showed that some individuals may experience irritability and mood swings during fasting as a result of low blood sugar levels [20].

Digestive Issues

Avoiding food for a long period like during a 36-hour fast can cause indigestion, bloating, diarrhea, and nausea in some individuals because of consuming low levels of calories [21].

So, if you have decided to try a 36-hour fast or even if you’re hesitant, learning about the process of this type of intermittent fasting can help you find out if it aligns with your health goals and lifestyle.

Learn More: 16-Hour Fast: Benefits and Results [The Best Foods to Eat]

How to Do the 36-Hour Fast?

Here are the steps you need to take to try a 36-hour fast healthily.

Before You Start:

• Consult a healthcare professional to ensure a 36-hour fast is good for you, especially if you have pre-existing medical issues.

Preparation:

• Decide your fasting period based on your schedule and preferences. For example, you can start after dinner and break the fast with breakfast the day after next.
• Stay Hydrated: In the hours before starting the fast, drink plenty of water to stay hydrated.

During the Fast:

• Avoid Calories: Avoid consuming calories as food or beverages during the 36-hour fast, you can only drink non-caloric beverages.
• Stay Hydrated: You can drink water, herbal tea, and black coffee to stay hydrated and curb hunger.
• Listen to Your Body: Pay attention to your body's reactions and break the fast if you feel severe discomfort, dizziness, or other adverse effects.

Breaking the Fast:

• Start with Nutrient-Dense Foods: Break the 36-hour fast with whole, nutrient-rich foods. Eat balanced meals containing lean proteins, healthy fats, and complex carbohydrates.
• Start Slowly: Start with small portions and let your body adapt to the new eating habits.

After the Fast:

• Return to your regular eating habits and avoid overeating.
• Stay Hydrated: Keep drinking water throughout the day to stay hydrated.

Avoiding calories for 36 hours activates various physiological changes in your body. Since the beginning of the fast, your body goes through different stages.

Learn More: Can You Drink Diet Soda While Fasting?

What Are The Stages of The 36-Hour Fast?

• Hour 0-6: The body begins to use the glucose it has received from recent meals to provide energy. Insulin levels gradually decline, so the stored glycogen is broken down and used to provide energy.
• Hour 6-12: The body gradually uses all the glycogen stored, so it turns to stored fat for energy. Fat molecules are broken down into fatty acids. The liver tries to convert fatty acids into ketones as alternative energy sources.
• Hour 12-18: Ketone production increases and fat becomes the main source of energy. Autophagy is started.
• Hour 18-24: More ketone is produced, which improves mental clarity and insulin sensitivity as insulin levels decrease. Fat loss increases as the body relies only on fat for energy.
• Hour 24-36: Autophagy increases. Metabolism tries to adapt to energy energy-saving. Hunger hormones like ghrelin decrease, lowering the feelings of hunger.

When it comes to positive physiological changes, some individuals assume they can regularly fast to gain all the benefits. But there’s a limit and you should try a 36-hour fast based on the following important considerations.

How Often Should I Do 36 Hours Fast?

No one can decide the frequency of 36-hour fasting better than you, as you know your goals, health status, and comfort level.

It's no secret that individuals show different reactions to fasting, and we can't say one schedule is good for everyone.

Anyhow, if you consider a 36-hour fast, you can check the benefits, considerations, and cautions of different frequencies below.

36-Hour Fast Once a Week

• Benefits: A 36-hour fast once a week can have metabolic benefits, promote weight loss, and boost autophagy.
• Considerations: Doing a 36-hour fast once a week can be suitable for many individuals.
• Cautions: In case of extreme hunger, fatigue, or other negative effects, adjust the fasting schedule or consult a healthcare specialist.

36-Hour Fast 2 Times a Week

• Benefits: Doing a 36-hour fast two times a week can Increase insulin sensitivity and metabolic flexibility and speed up weight loss.
• Considerations: 36-hour fasting twice a week is more challenging and requires gradual adaptation. Avoid it if you're new to fasting.
• Cautions: If you experience nutrient deficiency or overexertion, you must seek medical help.

36-Hour Fast 3 Times a Week

• Benefits: Doing 36-hour fasting more than twice a week can improve weight loss and metabolic results.
• Considerations: You must be a veteran of fasting to try this frequency, as you need to gain enough nutrition.
• Cautions: Overdoing fasting can lead to nutrient deficiencies, fatigue, sleep disorders, and disruptions to daily life. It's better to be patient and keep it slow to get the best results healthily, as good things take time!

If you’re not sure about the 36-hour fast or are considering similar extended intermittent fasting plans, you can take a look at the below comparisons. Please remember that these types of fasting are more common among individuals with more fasting experience.

Learn More: 40-Hour Fast: Does It Work? [Benefits and Side Effects]

The 24-Hour vs. 36-Hour Fast

To easily compare the 24-hour fast with a 36-hour fast, check the table below, which is summarizing their main features.

• Goals: If you aim to lose weight and gain metabolic benefits, you can use both fasting methods. If you seek autophagy benefits, a 36-hour fast is more suitable.
• Comfort Level: A 36-hour may not be so comfortable for beginners, and a 24-hour fast or shorter periods can be better.
• Lifestyle: Your daily routine and lifestyle determine which fasting method better works for you.
• Consultation: If you consider these longer fasting periods, you need to consult a healthcare specialist first to ensure it’s safe for you.

Learn More: 24-Hour Fast: How to Do It? Is It Good for Weight Loss? [Expert Guides]‍

The 48-Hour vs. 36-Hour Fast

The table below compares the main differences between a 48-hour fast and a 36-hour fast.

• Goals: Both methods provide autophagy and good weight management, but the 48-hour fast may offer longer or more effective autophagy.
• Experience: You need to be experienced in fasting to try any of these two methods.
• Comfort: The 36-hour fast may be more comfortable for those who want the benefits of an extended fast without committing to a full 48 hours.
• Consultation: You must seek medical consultation before both approaches to see if your body allows avoiding food for long hours.

The 72-Hour vs. 36-Hour Fast

Another extended fasting period is a 72-hour fast. Let’s compare it with a 36-hour fast and see how they differ.

• Goals: Both methods provide autophagy and good weight management, but the 72-hour fast may offer longer or more effective autophagy.
• Experience: You need to be experienced in fasting to try any of these two methods.
• Comfort: The 36-hour fast may be more comfortable for those who want the benefits of an extended fast without committing to a full 72 hours.
• Consultation: You should consult medical experts before both approaches to ensure your body allows these fasting periods.

One of the many reasons numerous individuals try extended intermittent fasting is autophagy. Can a 36-hour fast provide the same autophagy as longer fasting plans?

Learn More: The 96-Hour Fast Benefits and Results: Is It Safe?

36-Hour Fast and Autophagy

A 36-hour fast can stimulate autophagy, which recycles damaged or dysfunctional cells. Simply put, it’s a cellular cleanup process that improves cellular health and longevity.

Autophagy can happen during a 36-hour fast because we consume fewer nutrients and produce less energy. But why all this is important?

Autophagy, this cell-cleaning process, can lower the risk of many diseases, including neurodegenerative disorders, cancer, and metabolic conditions. It can also improve metabolic health, immune function, and cellular resilience [22] [23].

Autophagy is a gradual process that doesn’t happen all at once, but it takes time to peak and provides health benefits. It usually takes 12-24 hours for the autophagy results to appear.

While avoiding food for extended periods can lead to autophagy, we also need to consume nutritious and healthy foods after fasting to boost this process.

Learn More: [Expert Guide] 20-Hour Fast Results, Side Effects, and How to

What Should I Eat After 36 Hours of Fasting?

Break the fast with a small but nutritious meal. The first meal must be small and easily digestible so the body and digestive system can adjust. Also, drink water or herbal tea gradually to rehydrate your body, and avoid digestive issues.

Also, the meals after the fast must contain various macronutrients—protein, healthy fats, and complex carbohydrates—to provide sustained energy.

Here are examples of the foods best to eat and avoid after a 36-hour fast. But you can always adjust based on the specific diets you’re on.

Foods to Eat

• Proteins: Lean protein sources like chicken, turkey, fish, tofu, or legumes
• Healthy Fats: Avocados, nuts, seeds, and olive oil
• Complex Carbohydrates: Whole grains like brown rice, quinoa, sweet potatoes, or whole wheat bread
• Vegetables: Various colorful vegetables
• Fruits: Fresh fruits like berries, apples, or oranges

Foods to Avoid

• Highly Processed Foods: Sugary snacks, fast food, and heavily processed foods
• Excessive Sugar: Sugary drinks, candies, and desserts
• Fried and Greasy Foods
• Large Portions

We generally assume that after 36 hours of not eating, we’ll be super hungry. But this may not be the case for everyone, and some may not have an appetite for food quickly after the fast. Here’s why.

Learn More: Carnivore Diet Fasting: Types, Food List & Meal Plan

Why Am I Not Hungry after Fasting for 36 Hours?

Not feeling hungry after fasting for 36 hours is likely due to a combination of decreased ghrelin levels, ketosis, autophagy, and psychological adaptations. These factors work together to suppress appetite and make longer fasting periods more manageable.

If you continue to experience unusual hunger patterns or any discomfort, it's always a good idea to consult a healthcare professional.

Also, if you’re an athlete or are used to doing regular exercise, you need to consider the following points.

Can You Work Out During a 36-Hour Fast?

Yes, you can work out during a 36-hour fast, but it’s important to tailor your exercise routine to your energy levels and overall well-being. Prioritize hydration, listen to your body, and adjust the intensity of your workouts to ensure safety and effectiveness.

Working out during a 36-hour fast can

• increase fat burning,
• improve insulin sensitivity, and
• enhance autophagy.

But you need to pay attention to the following factors if you decide to exercise during fasting.

• Energy Levels: Your energy levels might be lower than usual due to the lack of food intake. Adjust the intensity of your workouts accordingly.
• Hydration: Staying hydrated is crucial. Drink plenty of water, and consider electrolytes to maintain balance.
• Low to Moderate Intensity: Activities like walking, light jogging, yoga, or stretching are generally safe.
• High Intensity: High-intensity workouts, such as heavy lifting or intense cardio, might be more challenging and can lead to dizziness or fatigue.
• Listen to Your Body: Pay attention to how you feel. If you experience dizziness, fatigue, or any discomfort, it’s best to stop and rest.
• Post-Workout Nutrition: Plan your post-fast meal to include a good balance of proteins, fats, and carbohydrates to replenish energy and help recovery.

A common concern for athletes and individuals with regular exercising is losing muscle mass during fasting. Can a 36-hour fast result in muscle mass loss?

Will I Lose Muscle During a 36-Hour Fast?

While some muscle loss might occur during a 36-hour fast, it is usually minimal if you take steps to manage it properly. Maintaining adequate protein intake, staying hydrated, engaging in resistance training, and using amino acid supplements can help preserve muscle mass.

The benefits of increased growth hormone and autophagy during fasting also support muscle preservation.

So, it’s generally safe to work out during fasting without much to worry about. However, some individuals need special care regarding fasting, and should NOT try it without direct supervision of healthcare professionals. Let’s see if you’re among these individuals.

Who Should Not Consider Doing the 36-Hour Fast at All?

• Those with Underlying Medical Conditions
• Pregnant and Breastfeeding Women
• Children and Adolescents
• Individuals with Eating Disorders
• Those Who Had Recent Surgery or Illness
• Those under Specific Medication
• Highly Activity Individuals (Athletes)
• Individuals with Low Body Weight
• Sensitive Individuals

So, if you’ve consulted physicians and nutritionists and found that a 36-hour fast is safe for you, considering the following tips can help you get better fasting results.

Learn More: Taking Medications on Intermittent Fasting: Do Medications Break a Fast?

Tips for a Successful 36-Hour Fast

• Plan activities and keep busy to take your mind off food and fasting.
• Avoid intense exercising while fasting and go walking or do yoga instead.
• Have a balanced and nutritious meal before starting the fast. Include protein, healthy fats, and complex carbohydrates.
• Break the fast with small, nutritious meals, and avoid overeating and consuming sugary or processed foods after the fast.
• Monitor your body’s reactions and break the fast if you notice extreme symptoms like dizziness, extreme fatigue, mood swings, or excessive thirst.
• Rest and sleep adequately during fasting.

Summary

The 36-hour fast is another version of intermittent fasting tried by those more experienced in fasting. This kind of prolonged fasting can boost metabolic health, help weight loss, and renew cells.

Plan carefully based on your goals and needs to avoid nutrient deficiencies and health issues. Also, remember to drink lots of water on and off the fasting period to avoid dehydration.