The 36-hour fast or monk fast is a type of intermittent fasting usually tried by those experienced in fasting to lose fat or cure certain health conditions. Let’s go through this type of fasting and learn how to do it, what to eat, and how often to do it, and find out if it’s the right thing for us to reach our health and fitness goals.
Table of Contents
What Is a 36-Hour Fast?
A 36-hour fast is a type of intermittent fasting where you need to avoid consuming calories for a consecutive 36 hours.
The only things you can consume during fasting are non-caloric drinks like water, herbal tea, and black coffee.
Let’s see why many people try this type of intermittent fasting and what its rules are.
Many individuals try a 36-hour fast for the following reasons.
Weight Management: The 36-hour fast helps weight management by creating a caloric deficit. Avoiding food for a long time makes the body burn fat to provide energy, which boosts fat melting and weight loss.
Metabolic Benefits: Fasting can improve insulin sensitivity, which helps reduce the risk of type 2 diabetes. It can also promote cellular repair and improve metabolism.
Autophagy: Long fasting, like a 36-hour fast, can promote autophagy, a process of cleaning damaged cells and generating new ones.
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.
Duration: The fast lasts for a total of 36 hours. You can plan it based on your routine. For example, you can fast from dinner on one day to breakfast on the following day.
Avoiding Calories: You must avoid calories during the fasting period, i.e., you can’t eat solid foods, liquids with calories, and sugary drinks.
Drink Non-Caloric Beverages: You can drink water, herbal tea, and black coffee during fasting hours to stay hydrated and somehow decrease hunger.
Electrolytes: If needed, you can consume electrolytes to steer clear of dehydration.
Balanced Eating: When breaking the fast after 36 hours, you need to start with small nutritious portions to let your digestive system get used to the new situation.
Medical Considerations: If you’re new to fasting, it’s better to start with less strict versions of intermittent fasting, like 8-hour or 12-hour fasting, and try extended fasting when ready. Also, it’s good to consult a healthcare professional to ensure extended fasting is safe for you.
Summary: A 36-hour fast involves not eating for 36 hours, aiding weight management, metabolism, autophagy, and mental clarity, with specific rules and hydration.
A 36-hour fast comes with various benefits and side effects, which we should be aware of in advance to choose the best diets, leading us to our health and fitness goals and avoiding possible health issues.
✌ I created the Free Carnivore Starter Kit to ensure that everyone can begin their Carnivore journey, helping them achieve their health and weight loss goals. When you join, I will send you a weekly email that will provide you with all the essential tools and tips you need!
Thank you. Please check your email!
Please enter a valid email address.
The Benefits of a 36-Hour Fast
Extended intermittent fasting, like a 36-hour fast, can have various benefits, including the following.
Improved Insulin Sensitivity:
Intermittent fasting, including a 36-hour fast, can increase insulin sensitivity and lower the risk of type 2 diabetes. A 2015 study published in the journal Obesity reported that intermittent fasting had a positive effect on insulin sensitivity and lowering insulin levels in participants with insulin resistance.
Source: Halberg, N., Henriksen, M., Söderhamn, N., et al. (2005). Effect of intermittent fasting and refeeding on insulin action in healthy men. Journal of Applied Physiology, 99(6), 2128-2136.
Extended fasting makes the body use stored fat, instead of carbohydrates, to produce energy, which means losing fat and losing weight. A 2016 study published in Cell Metabolism indicated that intermittent fasting boosts fat oxidation, resulting in weight loss and fat mass reduction.
Source: Tinsley, G. M., & La Bounty, P. M. (2015). Effects of intermittent fasting on body composition and clinical health markers in humans. Nutrition Reviews, 73(10), 661-674.
Cellular Repair through Autophagy:
A 2016 study published in Nature showed that fasting activates autophagy, which removes damaged cells and improves cellular health and longevity.
Source: Mizushima, N., & Yoshimori, T. (2007). How to interpret LC3 immunoblotting. Autophagy, 3(6), 542-545.
Brain Health and Mental Clarity:
Some animal studies on intermittent fasting showed its effects on brain health and cognitive function. Fasting does so by triggering the production of brain-derived neurotrophic factor (BDNF), a protein for neuron growth and cognitive function.
Source: Duan, W., Guo, Z., Jiang, H., et al. (2003). Dietary restriction normalizes glucose metabolism and BDNF levels, slows disease progression, and increases survival in huntingtin mutant mice. Proceedings of the National Academy of Sciences, 100(5), 2911-2916.
A 2015 study published in Free Radical Biology and Medicine found that intermittent fasting can decrease oxidative stress and inflammation.
Source: Vasconcelos, A. R., Yshii, L. M., Viel, T. A., et al. (2015). Intermittent fasting attenuates lipopolysaccharide-induced neuroinflammation and memory impairment. Journal of Neuroinflammation, 12(1), 1-15.
Summary: Scientifically, a 36-hour fast may support brain health and mental clarity and reduce inflammation, but more research is needed for confirmation.
Confused About Fasting?
Join The ULTIMATE 7-Day Fasting Course today to achieve weight loss, get into ketosis and heal inflammation.
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, drink enough water and other non-caloric beverages during fasting hours.
Source: Adolph, E. F., Barker, B., Eckert, H. M., et al. (1982). Fluid balance during dehydration and rehydration with oral fluids. Journal of Clinical Endocrinology and Metabolism, 54(5), 1137-1142.
Fatigue and Weakness:
A 2013 study published in the European Journal of Clinical Nutrition reported that the participants experienced fatigue during a 36-hour fast.
Source: Catenacci, V. A., Pan, Z., Ostendorf, D., et al. (2013). A randomized pilot study comparing zero-calorie alternate-day fasting to daily caloric restriction in adults with obesity. Obesity, 21(9), 1785-1795.
A 1999 study published in Physiology & Behavior indicated mood changes and irritability are common during 36-hour fasting.
Source: Lieberman, H. R., Caruso, C. M., Niro, P. J., et al. (1999). Behavioral, physiological, and cognitive responses to caloric deprivation in military men. Psychiatry Research, 85(3), 281-292.
A 1990 study published in the American Journal of Clinical Nutrition showed the participants resting metabolic rate decreased after a 36-hour fast.
Source: Zauner, C., Schneeweiss, B., Kranz, A., et al. (2000). Resting energy expenditure in short-term starvation is increased as a result of an increase in serum norepinephrine. The American Journal of Clinical Nutrition, 71(6), 1511-1515.
Summary: Scientific evidence suggests potential side effects of a 36-hour fast, including dehydration, fatigue, mood changes, and metabolic adaptations.
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.
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.
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.
Tips for Success:
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.
So, how often can we do a 36-hour fast? Is it safe and healthy to do it more than once a week?
How Often Should I Do a 36-Hour 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.
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.
Twice 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 consultation.
Three 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 consume enough nutrition.
Cautions: Overdoing fasting can lead to nutrient deficiencies, fatigue, and disruptions to daily life. It's better to be patient and keep it slow to get the best results in a healthy way, as good things take time!
Now that we know the basics of 36-hour fasting let's compare it with other common versions of intermittent fasting, i.e., 24-hour and 48-hour fasting.
The 24-Hour vs. 36-Hour Fast
The 24-hour and 36-hour fasts are two different kinds of intermittent fasting, but they have differences in duration and effects. Let’s compare and contrast them.
The 24-Hour Fast:
Duration: A 24-hour fast includes avoiding calories for a full day, like from dinner to dinner or lunch to lunch.
Fasting Period: A complete 24 hours
Benefits: Better insulin sensitivity, weight loss, and metabolic improvements
Feasibility: Good for individuals who have experienced 8-, 12-, and 16-hour fasts and look for more challenging fasts
Frequency: Depends on personal status and goals, but can be done once or twice a week or more
What Happens in Your Body If You Fast for 36 Hours?
Avoiding calories for 36 hours activates various physiological changes in your body. Let’s see what they are.
Hour 0-6: The body begins to use glucose 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 initiated.
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 may decrease, lowering the feelings of hunger.
We have mentioned autophagy a lot in this article. It’s time to get into its details and find out why it matters so much.
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.
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.
What about weight loss? Can a 36-hour fast lead to weight loss and help us shed some extra pounds?
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.
Fat Burning: During fasting, when glycogen stores are emptied, the body begins to burn fat instead of carbs, which leads to weight loss.
Insulin Sensitivity: Fasting can improve insulin sensitivity, meaning that the body can better control blood sugar levels and reduce excess fat, which helps with weight loss.
Appetite Regulation: Fasting can trigger hunger hormones like ghrelin and reduce appetite, which means less calorie intake during eating windows and better weight control.
Important Considerations: Weight loss during a 36-hour fast comes from both water weight and fat loss. However, rapid weight loss in the early days after fasting is often due to water loss. Your metabolism, overall diet, and activity level determine how much and how fast you can lose weight.
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.
Now that we’ve learned all about the fasting process, we need to talk about another important phase, which is breaking the fast. We need to know what to eat and how to eat to make the most of the 36-hour fast.
What Should I Eat After 36 Hours of Fasting?
Break the Fat with a Small but Nutritious Meal: The first meal must be small and easily digestible so the body and digestive system can adjust.
Hydration: Gradually drink water or herbal tea to rehydrate your body.
Balanced Nutrition: The meals after the fast must contain various macronutrients—protein, healthy fats, and complex carbohydrates—to provide sustained energy.
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
There is also another essential consideration. So far, we have discussed how to start and do the 36-hour fast, but not everyone can do such long fasts. Who can’t? Let’s find out.
Who Should Not Consider Doing the 36-Hour Fast at All?
Although fasting is generally safe, some special groups need to be cautious and consult health specialists before starting fasting. Here’s a list of sensitive groups:
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
To wrap up, I’ve provided essential tips for a successful 36-hour fast.
Tips for a Successful 36-Hour Fast
Here are the tips for a successful 36-hour fast.
Consult a professional.
Choose the right time.
Drink lots of water.
Use electrolytes if needed.
Start with shorter fasts and let your body adapt to the fasting situation.
Have a balanced and nutritious meal before starting the fast. Include protein, healthy fats, and complex carbohydrates.
Keep yourself busy by reading, working, meditating, or taking light walks to stay occupied and not think too much about food.
Monitor your body’s reactions and changes to modify if needed.
Break the fast with small, nutritious meals, and avoid overeating.
Eat whole, nutrient-dense foods when breaking the fast. The meals should contain lean proteins, vegetables, healthy fats, and complex carbs.
Avoid sugary or processed foods after the fast.
Avoid intense exercises during fasting. You can try light exercises like stretching, yoga, or walking during fasting.
Break the fast if you notice extreme symptoms like dizziness, extreme fatigue, mood swings, or excessive thirst.
Rest and sleep during fasting.
Have a positive mindset about fasting.
Follow a flexible approach.
Avoid overeating during the eating periods and have your regular eating patterns.
Be patient and let your body adapt to the new situation.
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.
The following Q&As address the most frequently asked questions about the 36-hour fast.
How Much Weight Can You Lose on a 36-Hour Fast?
The amount of weight you can lose on a 36-hour fast depends on various factors. However, studies show participants lost about 3.5 kg after four weeks of 36-hour fasting. Adding physical activities to fasting can boost the results.
Does a 36-Hour Fast Burn Belly Fat?
Dr. Mindy Pelz believes that a 36-hour fast can start fat burning by burning belly fat.
Is a 36-Hour Fast Long Enough for Autophagy?
A 36-hour fast can initiate autophagy, which usually includes two to four days of fasting. Autophagy begins when glucose and insulin levels drop significantly, which can start with 36- to 72-hour fasting.
Is a Monk Fast and a 36-Hour Fast the Same Thing?
The 36-hour fast, aka monk fast, includes fasting for 36 hours. In the monk fast, you only fast once a week.
What Is the Best Time of the Week to Fast for 36 Hours?
Although you can choose when to fast, some say it’s better to start on Monday after dinner and finish with breakfast on Wednesday morning.
Can Everyone Do a 36-hour Fast?
No, you need to avoid a 36-hour fast or consult a healthcare pro first if you’re new to fasting, are pregnant or breastfeeding, have underlying medical conditions, have eating disorders, are under special medication, do intense physical activities, or have low body weight.
Is a 36-Hour Fast Different from Intermittent Fasting?
No, the 36-hour fast is a strict kind of intermittent fasting.