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

What Is a 96-Hour Water Fast?

A 96-hour water fast, or four-day water fast, includes avoiding calories and drinking only water, not even other non-caloric drinks, which is the main difference between a 96-hour water fast and a 96-hour fast.

The rules and goals are the same in both methods, but the only difference is that a 96-hour fast allows non-caloric beverages like black coffee and herbal tea.

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.

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 as it is longer than a 96-hour fast.

The following table summarizes the similarities and differences between these two types of intermittent fasting.

Learn More: The 48-Hour Fast Benefits and Results: Is It Safe?

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.

Now that we know the differences between these fasting methods let’s get back to the 96-hour and focus on its benefits and side effects.

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

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

Extended fasting, like a 96-hour fast, can lower blood glucose levels and respiratory quotient and increase oxygen uptake. It can also positively affect the expressions of genes responsible for fat oxidation and thermogenesis [1].

Intermittent fasting can boost glucose tolerance in normal-weight male mice through Histone hyperacetylation [2].

Boosting Weight Loss and Lowering Inflammation

Prolonged intermittent fasting can treat obesity through caloric restriction. It can also help control body weight, improve glucose homeostasis and lipid profiles, and have anti-inflammatory effects [3].

Improving Immune Function

A 96-hour fast can help maximize intestinal stem cells. It can also reset the immune system and the microbiome [4].

Prolonged Fasting decreases IGF-1/PKA to increase hematopoietic stem cell-based regeneration and reverse immunosuppression [5].

The Side Effects of a 96-Hour Fast

While intermittent fasting can bring various benefits, including weight loss, it may cause the following side effects in some individuals as they avoid calories for extended hours.

• Headaches, Dizziness, and Low Energy Levels
• Decreasing Bone Density
• Dehydration
• Sleep Disorders
• Weakness and Fatigue
• Digestive Problems

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 61.3%), lethargy (68%), mood swings (57.8%), dizziness (55.8%), and polyuria (46.2%) [6] [7].

Decreasing Bone Density

A 2019 study on the effects of a 96-hour fast on bone quality in rats indicated 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 extended hours may cause dehydration if the individual neglects to consume 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].

Weakness and Fatigue

A 2017 study on intermittent fasting known as intermittent energy restriction (IER) indicated 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 on extended intermittent fasting found that avoiding food for long hours can cause some digestive issues, including indigestion, bloating, constipation, diarrhea, and nausea [12].

How Much Weight Can You Lose on a 96-Hour Fast?

The amount of weight you can lose on a 96-hour fast depends on each individual's personal factors, including their starting weight, body composition, metabolism, and sticking to the 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 may lose weight faster.

Muscle Mass Preservation

Extended fasting can cause muscle breakdown 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.

Learn More: 36-Hour Fast: How to Do? What to Eat? How Often to Do?

How to Do a 96-Hour Fast?

• Consult a Healthcare Professional First: Before trying an extended 96-hour fast, you must do the necessary medical tests to ensure it’s 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.
• Transition to Fasting: In the days before fast, 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 before fasting to avoid dehydration during the fast.
• Start Fasting in the Morning: Beginning the fast in the morning aligns with your body's natural circadian rhythms, which helps you manage the initial fasting stages more easily.
• Drink Enough Water: Consume adequate water during fasting to stay hydrated.
• Use Electrolytes: You can consume electrolytes like sodium, potassium, and magnesium to boost bodily functions and prevent electrolyte imbalances.
• Monitor Your Body’s Reactions: Break the fast and seek medical help (if needed) if you experience extreme discomfort, dizziness, weakness, or other serious symptoms.
• Plan the Meals after Fasting: Before starting the fast, think about how you’re going to break the fast. Go for balanced, small, light, and easily digestible meals containing whole, nutritious foods, including fruits and vegetables.
• Evaluate Your Experience: Record your changes and evaluate your fasting experience to adjust if needed to reach your goals.

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

How to Break a 96-Hour Fast?

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.

1. Start Slowly: 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. I’ll list the foods to eat and avoid below.
2. Steer Clear of Sugar and Processed Food
3. 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.
4. Chew Thoroughly: Your digestive system has not done a lot for four days, and now you're giving it a lot of responsibilities. So, chew your food slowly and thoroughly to aid digestion.
5. Stay Hydrated: Drink water and other beverages like herbal tea, coffee, and electrolyte solutions to avoid dehydration and other problems it can cause.
6. Monitor the Changes: See how your body reacts to reintroducing food and adjust accordingly.
7. 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.
8. Avoid Alcohol and Caffeine: It’s better to avoid alcohol and caffeine during the early hours after fasting, as they can be harsh on an empty stomach.
9. Consume Nutritious Foods: Nutrient-dense foods are necessary to provide vitamins and minerals after the fast.

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

Foods to Eat after a 96-Hour Fast

• 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

Foods to Avoid after 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’re sensitive, and eat lactose-free or fermented products like plain yogurt with probiotics.

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

A 96-Hour Fast and Autophagy

A 96-hour fast can trigger autophagy, which is a cellular cleansing process to remove dysfunctional or damaged cellular components, such as proteins, organelles, and cell membranes. Removing them boosts cellular health and longevity.

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 glycogen (stored glucose), 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 is known to inhibit the process.
• Increased Cellular Stress: Fasting imposes mild stress on cells, like nutrient deprivation and energy depletion. These stressors can trigger autophagy as a protective mechanism to repair and maintain cellular integrity.
• Mitochondrial Quality Control: Autophagy helps remove damaged mitochondria, the energy-producing organelles within cells. A 96-hour fast can improve mitochondrial function and quality.
• Protein Degradation: Autophagy can help degrade misfolded or aggregated proteins inside cells, and extended fasting can boost this process and clear out toxic protein aggregates.

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

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 weight loss, insulin sensitivity, autophagy, mental clarity, and detoxification in experienced individuals 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 appropriate supervision, 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 exercises can help you stay healthy and reach your fitness goals.

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

Who Should Avoid the 96-Hour Fast?

• Pregnant or Breastfeeding Women
• Children and Adolescents
• Those with Eating Disorders
• Those with Underlying Medical Conditions
• Individuals Taking Medications
• 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

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.