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A 96 hour fast is not for everybody. You need to be experienced in fasting, and your healthcare provider should approve it. If you are in the right condition to do this prolonged intermittent fasting, you can boost weight loss, control blood sugar levels, improve your immune system, and more. However, you may also experience some side effects. To decide if a 96 hour fast is worth trying, let’s learn about it and find out how to do it the right way.
Highlights
A 96 hour fast is a challenging four-day extended fast that helps with weight loss, insulin sensitivity, autophagy, mental clarity, and detoxification.
Its rules include avoiding calories, artificial additives, and sweeteners, and drinking only water, herbal tea, and black coffee during fasting.
You should break a 96 hour fast gradually with light, balanced, and nutritious meals to avoid digestive issues.
Its side effects may include headaches, dizziness, and dehydration.
The safety of a 96 hour fast depends on your health and experience with fasting, but it is not recommended for beginners or those with certain medical conditions.
Consulting a healthcare professional is necessary to ensure your body is ready for prolonged fasting.
What Is a 96 Hour Fast?
A 4-day or a 96 hour fast is a type of extended fasting where you should consume no calories for four whole days! It doesn’t seem easy, right?
Actually, no! It is not easy to avoid food and caloric drinks and only consume water and non-caloric beverages for four nights and days in a row.
So, why do people try it? Well, it can have specific health benefits, especially weight loss, for those experienced in fasting. It can also improve metabolic health and lead to autophagy (a cleaning process in the cells).
Despite all the benefits, it can have some side effects, and some people need to steer clear of it! But before going into the benefits and side effects, let’s learn about the rules and goals of a 96-hour fast.
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Rules
Consume no calories. You need to resist the urge to consume foods and drinks containing calories. It means no solid foods and no caloric drinks, only water, herbal tea, black coffee, and other non-caloric beverages.
Use no calorie-free sweeteners or flavors. Artificial additives, calorie-free sweeteners, or flavors to your water are also excluded because they can spike insulin, which kills fasting benefits.
Supplement with electrolytes. To keep the balance of electrolytes, you can use sodium, potassium, and magnesium to prevent dizziness or muscle cramps.
Monitor your body’s reactions to the fasting situation and stop the fast if you feel severe discomfort, dizziness, or other serious symptoms.
Dr. Elson Haas, Author of "The New Detox Diet"
"Fasting is a cleansing therapy - it is a way to purify, energize, and rejuvenate the body and mind."
Goals
Losing weight by avoiding food and creating a caloric deficit
Improving insulin sensitivity
Inducing autophagy, a cleaning process to remove damaged or dysfunctional cells and boost longevity
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The Benefits of a 96 Hour Fast
The main benefits of a 96-hour fast include
Managing blood sugar levels,
Boosting weight loss and lowering inflammation, and
Improving immune function.
Managing Blood Sugar Levels
A 96 hour fast can lower blood glucose levels and increase oxygen uptake. It can also positively affect the expression of genes responsible for fat oxidation and thermogenesis [1].
Fat oxidation is the process by which your body breaks down stored fat to use as energy. During a 96-hour fast, your blood sugar levels drop, so your body starts using more fat to provide energy.
Thermogenesis is the process of producing heat in your body, which also burns calories. A 96 hour fast can activate genes that help your body burn fat and generate heat, supporting both energy production and metabolism during the fast.
Additionally, studies show that intermittent fasting can boost glucose tolerance in normal-weight male mice through Histone hyperacetylation [2].
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Improving Immune Function
A 96 hour fast can help increase the production of intestinal stem cells. It can also boost the immune system and the microbiome [3].
Extended fasting decreases IGF-1/PKA to increase hematopoietic stem cell-based regeneration and reverse immunosuppression.
It simply means that fasting for several days can activate stem cells in your bone marrow, helping your body make new immune cells and strengthen the immune system [4].
Boosting Weight Loss and Lowering Inflammation
Prolonged intermittent fasting can help treat obesity by restricting calories and creating a caloric deficit. It can help control body weight, improve glucose homeostasis and lipid profiles, and have anti-inflammatory effects [5].
But the question is how much weight you can probably lose on an extended 96 hour fast.
Summary: A 96 hour fast can lower blood glucose levels, increase oxygen uptake, boost gene expression related to fat metabolism, help with obesity treatment, weight control, glucose regulation, support the immune system and microbiome health, and provide anti-inflammatory effects.
The amount of weight you can lose on a 96-hour fast depends on different personal factors, including your starting weight, body composition, metabolism, and diet. Let’s focus on some of these important factors affecting your weight loss.
Initial Weight: If you weigh more at the beginning of the fast, you need to burn more body fat than those with lower weights.
Caloric Deficit: Losing weight on a 96 hour fast happens through caloric deficit, which is directly related to your metabolism and activity level. The greater your caloric deficit (the difference between calories burned and calories consumed), the more weight you can lose.
Water Weight: The early weight loss you experience after fasting comes from losing water weight, not body fat. It differs in different individuals, but can be a few pounds.
Metabolism: As mentioned above, your metabolism rate affects how quickly you can burn calories during fasting. Those who have faster metabolisms can lose weight faster.
Muscle Mass Preservation: Extended fasting can break down your muscles to provide energy. You can avoid muscle mass reduction by consuming protein and doing regular physical activity.
Breaking the Fast: How you break the fast and how many calories you consume before and after fasting directly impact your weight loss. If you eat heavy and high-calorie foods too quickly, you may regain weight.
Weight Loss Rate: Generally, you can lose 2 to 10 pounds (0.9 to 4.5 kilograms) during a 96 hour fast. However, most of this number comes from water weight loss, and the real weight loss slows down as the fast progresses.
A 96 hour fast can trigger autophagy, which is a cleansing process in your cells to remove dysfunctional or damaged components, such as proteins, organelles, and cell membranes.
Removing them boosts cellular health and longevity. But how can a 96-hour fast trigger autophagy? Let’s find out.
Glycogen Depletion: In the early 24 to 48 hours of fasting, your body uses all the stored glycogen, which leads the body to burn fat. Fat breakdown produces molecules called ketones, and this process is called Ketosis, which promotes autophagy.
Hormonal Changes: Fasting changes our hormone production system. For example, it can decrease insulin levels, which increases autophagy, as insulin can slow down the process.
Increased Cellular Stress: Fasting imposes mild stress on cells, like nutrient deprivation and energy depletion. These stressors can trigger autophagy to protect, repair, and maintain cellular health.
Mitochondrial Quality Control: Autophagy helps remove damaged mitochondria, the energy-producing organelles in cells. A 96 hour fast can improve mitochondrial function and quality.
Protein Degradation: Autophagy can help degrade damaged or dysfunctional proteins inside cells, and extended fasting can boost this process and clear out toxic proteins.
Despite these beneficial effects, a 96 hour fast can come with some downsides. It is wise to learn about these side effects and be prepared.
While intermittent fasting can bring various benefits, including weight loss, it can cause the following side effects in some individuals because they don’t consume calories for many hours.
A 96-hour fast can lower blood glucose levels, enhance oxygen uptake, boost gene expression related to fat metabolism, help obesity treatment, weight control, glucose regulation, support the immune system and microbiome health, and provide anti-inflammatory effects.
Headaches, Dizziness, and Low Energy Levels
A 2023 study on the effects of intermittent fasting (IF) found that some of the common side effects of an IF diet include lethargy, mood swings, dizziness, and polyuria [6] [7].
Decreasing Bone Density
A 2019 study on the effects of a 96 hour fast on bone quality in rats showed that 96-hour fasting does not significantly change the macroscopic morphology of bone but can dramatically decrease bone density [8].
Dehydration
Different studies on intermittent fasting indicate that fasting for long hours can cause dehydration if you forget to consume enough zero-calorie drinks like water, herbal teas, etc. [9].
Sleep Disorders
A 2019 study on 1422 participants trying intermittent fasting for 4-21 days found that some of the subjects (about 15%) experienced disrupted sleep as a result of fasting [10].
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Weakness and Fatigue
A 2017 study on intermittent fasting, known as intermittent energy restriction (IER), showed that lowering the intake of calories can lead to weakness and fatigue in some individuals because of lowered blood sugar levels [11].
Digestive Problems
A 2019 study on extended intermittent fasting found that avoiding food for long hours can cause some digestive issues, including indigestion, bloating, constipation, diarrhea, and nausea [12].
Summary: A 96 hour fast can cause headaches, lethargy, mood swings, dizziness, and reduced bone density. It can also cause dehydration, weakness, fatigue, nausea, indigestion, diarrhea, indigestion, and constipation.
So, to avoid possible side effects and use the benefits, you need to do this extended fasting the right way. Let’s learn how to do the fast and how to break it safely.
Here are the steps to start a 96 hour fast the right way:
Consult a Healthcare Professional First
Before trying an extended 96-hour fast, you must consult a healthcare professional and do the necessary medical tests to ensure it is safe for you.
Set Goals
Before fasting, think carefully and decide why you want to fast. Defining your goals helps you choose the best methods and make the most of fasting. Your goals can include weight loss, improving metabolic health, etc.
Choose a Specific Time
Set a fixed period for your fasting to make yourself mentally and socially ready to avoid food. Choose a period when you don’t have a busy schedule, specific obligations, or intense physical activity.
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Transition to Fasting
In the days before fasting, gradually decrease your calorie intake and consume more whole foods, fruits, vegetables, and lean proteins. Decrease and gradually avoid carbohydrates and processed foods.
Stay Hydrated
Drink plenty of water and other zero-calorie beverages before fasting to avoid dehydration and its side effects during the fast.
Beginning the fast in the morning aligns more with your body's natural circadian rhythms, which helps you manage the initial fasting stages more easily.
Use Electrolytes
You can consume electrolytes like sodium, potassium, and magnesium to boost bodily functions and prevent electrolyte imbalances. You can simply add a pinch of salt to a glass of water and use it as an electrolyte drink.
Summary:
Summary: A 96-hour fast can cause headaches, lethargy, mood swings, dizziness, and reduced bone density. It can also cause dehydration, weakness, fatigue, nausea, indigestion, diarrhea, indigestion, and constipation.
Monitor Your Body’s Reactions
Check how your body is changing and monitor your body’s reactions. Break the fast and seek medical help if you experience extreme discomfort, dizziness, weakness, or other serious symptoms.
Also, record your changes and evaluate your fasting experience to adjust your method if needed to reach your goals.
Plan the Meals after Fasting
Before starting the fast, think about how you are going to break it. Start with balanced, small, light, and easily digestible meals containing whole, nutritious foods, including fruits and vegetables.
Here’s your step-by-step guide to breaking a 96-hour fast. Why do you need a guide? Because breaking the fast is as important as doing the fast. If you don’t follow the rules, you may get adverse results.
Start Slowly and Consume Nutritious Foods
Do not consume big meals right after finishing a 96-hour fast to let your digestive system adapt. It’s best to have a balanced, light, and easily digestible meal containing whole, nutritious foods. Also, consume nutritious foods to provide vitamins and minerals after the fast.
Steer Clear of Sugar and Processed Food
When you break a fast, your body is more sensitive because it has been in a resting, low-insulin state for a long time.
Eating sugar or processed foods right after it can shock your digestive system and cause a rapid spike in blood sugar and insulin levels. This can lead to bloating, nausea, energy crashes, and even digestive discomfort.
So starting with gentle, whole foods helps your digestion adjust smoothly and prevents unpleasant side effects.
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Chew Thoroughly
Your digestive system has not done a lot for four days, and now you are giving it a lot of responsibilities. So, chew your food slowly and thoroughly to help digestion.
Stay Hydrated
Drink water and other beverages like herbal tea, coffee, and electrolyte solutions to avoid dehydration and other problems it can cause.
Avoid Overeating and Undereating
Pay attention to your body’s hunger and fullness signals, and do not solely rely on your emotions. You know, after four days of not eating, you may want to dine well and eat as much as you can. But you shouldn’t! You need to follow a balanced diet to make the most of fasting, and do not pressure your body.
Avoid Alcohol and Caffeine
It is better to avoid alcohol and caffeine during the early hours after fasting, as they can be harsh on an empty stomach.
Try Small and Frequent Meals
Avoid three heavy meals and try several smaller meals or snacks throughout the day to allow your digestive system to adapt. You can include the following foods in your meals.
Please note that these are the general foods you can consume after extending fasting. If you are on a specific diet, you need to consume only the foods allowed in your diet.
Fresh Fruits: Non-acidic and water-rich fruits, including watermelon, cantaloupe, honeydew, and ripe bananas
Steamed or Lightly Sautéed Vegetables: Spinach, zucchini, broccoli, or carrots
Bone Broth
Lean Proteins: Try boiled or baked chicken, turkey, or fish after a few hours. Avoid fatty cuts of meat right after a 96-hour fast.
Complex Carbohydrates: Brown rice, quinoa, or whole-grain bread (in moderation)
Soft Cooked Eggs: Scrambled or soft-boiled eggs
Plain Yogurt
Nuts and Seeds: Almonds, chia seeds, or pumpkin seeds
Herbal Teas: Chamomile or ginger tea
Hydrating Foods: Cucumber, celery, and leafy greens
Dr. Jason Fung, Author of "The Complete Guide to Fasting"
"Fasting is not a fad, it’s a fact of nature."
Foods to Avoid after a 96 Hour Fast
Sugary and Processed Foods: Such foods can increase blood sugar levels and cause digestive discomfort.
Fatty Meats
Highly Spiced Foods: Spicy foods can irritate the digestive system.
Acidic Fruits: Citrus fruits like oranges, grapefruits
Alcohol
Caffeine: Coffee or energy drinks
Heavy, Greasy, or Fried Foods
Large Meals
Processed Snacks: Chips and packaged foods
Dairy Products: Avoid dairy if you are sensitive, and eat lactose-free or fermented products like plain yogurt with probiotics.
Now that we have learn about a 96 hour fast, let’s compare this extended fasting with other similar approaches like a water fast, a 120-hour fast, and a 72-hour fast.
The main difference between a 96-hour water fast and a 96-hour fast is that in a 96-hour water fast, or a four-day water fast, you avoid calories and only drink water, not even other non-caloric drinks. The rules and goals are the same in both methods.
96-Hour vs. 120-Hour Fast
The biggest difference between a 96-hour fast and a 120-hour fast is their duration. A 96-hour fast lasts four continuous days, while a 120-hour fast lasts five days.
Following both methods, you need to avoid calories during fasting to achieve benefits like weight loss, improved insulin sensitivity, autophagy, mental clarity, and detoxification.
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Both methods are challenging, even for experienced fasters, and are not usually recommended to beginners. Even veteran fasters need to consult healthcare professionals before doing extended fasting to ensure it won’t have negative effects.
The positive and negative results may be more significant in a 120-hour fast because it is longer than a 96-hour fast, and the body has more time to recover.
The following table summarizes the similarities and differences between these two types of intermittent fasting.
Some results may be less significant than 120-hour fasting.
Some results may be more significant than a 96-hour fast.
96-Hour vs. 72-Hour Fast
Like the previous pair, a 96-hour fast and a 72-hour fast are both extended fasting methods, which differ in duration. While a 96-hour fast continues four days and nights, a 72-hour fast lasts three days and nights.
You need to avoid caloric intake during fasting hours and consume only water and non-caloric drinks like herbal tea and black coffee. You can also use electrolyte supplements.
Both methods are challenging but can provide different benefits, like weight loss, autophagy, and better insulin sensitivity. But the results, both negative and positive, can be more significant in a 96-hour fast as it lasts longer.
The table below summarizes the main similarities and differences between 96-hour vs. 72-hour fasting.
Results may be more significant due to longer duration
Results may be less significant due to shorter duration
Is a 96 Hour Fast Healthy?
A 96-hour fast can be healthy for some and unhealthy for others. It all depends on your health status, goals, and how you fast.
Extended fasting can help with weight loss, insulin sensitivity, autophagy, mental clarity, and detoxification in experienced fasters and those who can tolerate long hours of fasting.
Even experienced and completely healthy people may experience side effects, including dizziness, fatigue, muscle cramps, and electrolyte imbalances.
A 96 hour fast can have health benefits, but you’d better approach it with caution and under the direct supervision of your dietitian, especially if you are new to fasting or have underlying health concerns.
Remember that health comes first, and you shouldn’t set goals that may endanger your general well-being. Maintaining a balanced diet and doing regular physical exercise can help you stay healthy and reach your fitness goals.
Those with Records of Low Blood Pressure or Fainting
Individuals with Nutrient Deficiencies
Individuals with Mental Health Concerns
Athletes and Individuals with High Physical Activity Levels
Individuals Who Are New to Fasting
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Summary
A 96 hour fast is an intense approach to weight loss and gaining health benefits, and only pro fasters can do it after consulting healthcare professionals.
If it’s your first time trying fasting, you certainly need to try shorter versions of intermittent fasting, like an 8- or 12-hour fast, to see how your body reacts.
So, remember that you need to stick to the rules mentioned here to experience a healthy fast. It is not something you can do without knowledge, experience, and medical supervision.
FAQ
Check the following Q&As to find answers to the most frequently asked questions about a 96 hour fast.
Does a 96 Hour Fast Burn Belly Fat?
Although results differ in different individuals, a 96-hour fast can generally help you lose 0.55 to 1.65 pounds (0.25–0.75 kg) per week, with a reduction in belly fat.
Is a 96-Hour Fast Long Enough for Autophagy?
Yes, a 96-hour fast can provide deep autophagy and cell regeneration.
Is a Monk Fast and a 96-Hour Fast the Same Thing?
No, a monk fast is extended fasting lasting several days to reach spiritual goals, while a 96-hour fast is a prolonged intermittent fast lasting four days for weight loss and health purposes.
What Is the Best Time of the Week to Fast for 96 Hours?
You can choose the best time to fast for 96 hours based on your schedule and plans. Pick the days when you’re not so busy at work or socially, and don’t do intense physical activities.
Can Everyone Do a 96-Hour Fast?
No, a 96-hour fast is challenging and not recommended for beginners or those with certain medical conditions. Consult a healthcare specialist to ensure it’s fine for you.
Is a 96-Hour Fast Different from Intermittent Fasting?
A 96-hour fast is a prolonged version of intermittent fasting.
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