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

Highlights

• A 48-hour fast involves avoiding calories for two consecutive days, leading to benefits like weight loss and better metabolism.
• Rules for a 48-hour fast include avoiding calories, staying hydrated, and monitoring your body's reactions.
• Goals of a 48-hour fast include weight loss, enhanced mental clarity, and cellular autophagy.
• Compared with other fasting methods, a 48-hour fast offers unique benefits but also presents challenges.
• Side effects of a 48-hour fast may include hunger, fatigue, and mood swings, and its frequency should be determined based on individual health and goals.

What Is a 48-Hour Fast?

It’s no rocket science! As the name suggests, a 48-hour fast includes avoiding food for a continuous 48 hours. By food, I mean all calories coming from foods and drinks.

A 48-hour fast is becoming more popular among experienced fasters because it can have different health benefits, such as boosting metabolic health, better mental clarity, and, of course, weight loss.

Let’s get into details and learn about the rules and goals of this popular type of intermittent fasting.

Rules

• Avoid Calories During Fasting: In the 48 hours of the fasting period, you can’t eat meals, snacks, or any foods or drinks that contain calories.
• Drink Enough Water: Staying hydrated is necessary during fasting. You can drink water and other non-caloric drinks like herbal tea and black coffee.
• Keep Electrolyte Balanced: The right balance of electrolytes is necessary for the body's blood chemistry, muscle action, and other processes. Sodium, calcium, potassium, chlorine, phosphate, and magnesium are all electrolytes we gain from different foods and drinks. To keep the electrolyte balance, you can also supplement with sodium, potassium, and magnesium.
• Monitor Your Body’s Reactions: Control how your body reacts to fasting and avoiding food. If you feel dizzy, excessively weak, or experience any severe discomfort, you must break the fast and eat a small, nutritious meal.
• Start Foods Gradually: When the 48-hour fast is finished, start with simple, small, and easily digestible meals to avoid pressuring your digestive system.
• Consult a Healthcare Specialist: If you have any pre-existing health issues, you’d better consult a dietitian or healthcare professional to see if your body can tolerate extended fasting.

Goals

• Losing Weight: The 48-hour fast can lead to a caloric deficit, which can promote weight loss. Fasting can also help the breakdown of stored fat for energy.
• Metabolic Benefits: Some studies show that 48-hour fasting can help insulin sensitivity, decrease inflammation, and boost cellular repair processes, which lead to long-term metabolic benefits.
• Mental Clarity: Fasting can improve mental clarity and focus in some individuals as the body tries to burn ketones instead of carbs to produce energy.
• Cellular Autophagy: 48-hour fasting can trigger autophagy, which is a process to clear cells from damaged components.
• Resetting Eating Habits: A 48-hour fast can work as a reset button for unhealthy eating habits, helping you focus more on eating healthily.

You may have also heard of two variations of the 48-hour fast, i.e., a 48-hour water fast and a 48-hour dry fast. Let’s see how they differ from the 48-hour fast.

What Is a 48-Hour Water Fast?

A 48-hour water fast includes avoiding calories for 48 hours and drinking only water. During this specific type of intermittent fasting, the fasters exclude foods and drinks (even non-caloric drinks like tea and coffee) and only consume water to stay hydrated.

A 48-hour water fast seeks the same goals as a 48-hour fast and provides the same benefits mentioned above, but it’s a bit more restrictive.

What Is a 48-Hour Dry Fast?

A 48-hour dry fast is another version of the 48-hour fast that excludes all drinks for 48 consecutive hours.

Water fasting allows only water during fasting, while a 48-hour dry fast is the opposite and excludes all beverages for 48 hours.

This type of fasting is more extreme and may lead to dehydration compared to water fasting or other types of intermittent fasting that allow hydration.

If you consider a 48-hour dry fast, you need to consult a professional before starting to check if your body can tolerate no drinks for two complete days.

Speaking of different versions of fasting, let’s compare a 48-hour fast with other common types of extended intermittent fasting, i.e., a 24-hour, a 36-hour, and a 72-hour fast.

24- vs. 48-Hour Fast

A 24-hour fast and a 48-hour fast have various features in common, but they also differ in some basic principles. Let’s check them both in detail and find out which can be a better option for you.

• Duration: A 24-hour fast lasts one whole day, but a 48-hour fast continues for two whole days.
• Frequency: You can do a 24-hour fast once or twice a week, while a 48-hour fast is done less frequently as it’s longer and may have more physical and mental challenges.
• Benefits: Both fasting methods can promote weight loss by creating a caloric deficit. They can also lead to insulin sensitivity and metabolic health. But the results can be more significant in a 48-hour fast.
• Simplicity: A 24-hour fast can be easier due to its shorter duration.
• Autophagy: A 48-hour fast can bring better results in cellular autophagy, as it takes longer and provides more time for this process.
• Challenges: Both fasting methods can cause hunger fatigue and electrolyte imbalance. But the side effects can be more visible in a 48-hour fast.

Which Is a Better Choice?

To choose the best fasting method, you need to review your goals, health status, and needs. If you aim to lose weight, both methods can work for you, but initial weight loss can be more significant in a 48-hour fast.

Both methods offer some health benefits, some of which, like insulin sensitivity and autophagy, can be more obvious in longer fasts.

If you're new to fasting, you’d better start with shorter fasts, maybe even not a 24-hour, but an 8- or 16-hour fast, to let your body adapt to the new situation and then go for longer periods.

36- vs. 48-Hour Fast

• Duration: A 36-hour fast lasts for one and a half days, while a 48-hour fast lasts two days and nights in a row.
• Frequency: You can practice a 36-hour fast more often than a 48-hour fast, but they are not so different in frequency.
• Benefits: Both fasting methods can help you lose weight thanks to the caloric deficit state they create. They can also improve insulin sensitivity and metabolic health and stimulate autophagy. But a 48-hour fast may be more effective.
• Challenges: Both methods can cause hunger, fatigue, and electrolyte imbalance, but the results are more obvious in a 48-hour fast.

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

Which Is a Better Choice?

Choosing a proper fasting method is not hard if you first consider your goals, needs, and health status. If you consider fasting for weight loss, both a 36-hour fast and a 48-hour can be helpful, but a longer fast can produce better results.

If you’re looking for a fasting method to boost your health status, you can use both methods to improve insulin sensitivity and autophagy, but a 48-hour fast can yield better results.

Inexperienced fasters should start with shorter versions, and these two types of extended fasting are more suitable for experienced fasters.

48- vs. 72-Hour Fast

• Duration: A 48-hour fast includes avoiding calories for two consecutive days, while a 72-hour fast lasts for three whole days.
• Frequency: A 72-hour fast is less frequent than a 48-hour fast due to its longer period.
• Benefits: Both methods can help weight loss, mental clarity, insulin sensitivity, and autophagy, but a 72-hour fast can be better as it’s longer.
• Challenges: Both methods can cause hunger, fatigue, and electrolyte imbalance, but the results may be more intensive during a 72-hour fast.

Which Is a Better Choice?

Generally, both a 48-hour and a 72-hour fast are good for weight loss and bring different health benefits like better metabolism and autophagy. But choosing between them depends on your specific goals and health status.

Now that the path is clearer and we know the differences between 48-hour fasting and other similar fasting methods let’s focus on 48-hour fasting and its benefits and side effects.

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

The Benefits of a 48-Hour Fast

• According to a 2015 study, extended fasting, like a 48-hour fast, can help decrease obesity, rheumatoid arthritis, and asthma (source).
• Another study conducted in 2018 found that fasting lets the digestive system rest and helps promote weight loss, improve brain function, decrease inflammation, lower glucose levels and blood pressure, improve insulin sensitivity, boost human growth hormone, slow down the aging process, increase immunity, and stimulate autophagy (source).
• A 2017 study reports that intermittent fasting, like a 48-hour fast, can yield similar short-term weight loss results as traditional calorie restriction in those with overweight and obesity, i.e., avoiding excess calories can be just as effective as fasting for weight loss (source).
• A 2016 study indicated that a 48-hour fast can reduce weight, heart rate, and systolic blood pressure. It can also lower the concentration of oxygenated hemoglobin and improve mental flexibility and shifting set (source).
• Another 2020 study of 27 intermittent fasting dietary interventions revealed increased weight loss with no serious harmful effects (source).
• A 2008 study found that a 48-hour fasting can lower oxidative stress and chronic inflammation (source).
• A 2010 study indicated that 48-hour fasting can reduce LDL (bad) cholesterol and triglycerides levels (source).
• Another study conducted in 2018 showed that fasting can boost autophagy and cellular health (source).
• Fasting can also decrease the risk of heart failure by about 70% (source).
• Extended fasting can also help reduce the risk of cancer and neurodegenerative diseases, including dementia and Alzheimer’s disease (source).

Summary: The benefits of a 48-hour fast include weight loss, lower inflammation, better heart health, improved cognitive function, increased insulin sensitivity, boosted immunity, reduced oxidative stress, lower LDL cholesterol and triglyceride levels, better cellular health, and lower risks of heart failure, cancer, dementia, and Alzheimer's disease.

The Side Effects of a 48-Hour Fast

• A 48-hour fast can cause hunger, fatigue, insomnia, and dizziness (source).
• It can also decrease your energy and make you feel exhausted (source).
• 48-hour fasting can also impose some risks on individuals with type 1 diabetes and low blood pressure, those with eating disorders, and pregnant and breastfeeding women (source).
• A 2016 study on a 48-hour fast shows that it can increase anger and mood swings (source).
• Intermittent fasting can cause negative emotional states like irritability (source).
• It can also cause a temporary decrease in blood oxygen levels (source).

Summary: A 48-hour fast may cause hunger, fatigue, insomnia, dizziness, energy loss, mood swings, and irritability in some individuals.

What Happens During a 48-Hour Fast?

The human body undergoes various physiological and metabolic changes during a 48-hour fast. Let’s explore these changes from the early hours to the end of this 2-day fast.

• Hour 0-12: During the initial 12 hours when your body is in the fed state, it burns glucose to provide energy. In this period, your insulin levels increase, and the excess glucose is stored in the liver and muscles as glycogen. As the body burns the stored glycogen for energy, your blood sugar levels gradually decrease.
• Hour 12-24: After 12 hours of fasting, your body shifts to burn fat for energy. Gradually, the insulin levels decrease, letting the body burn stored fat. Meanwhile, fats are broken down into ketones, which gradually become the main source of energy. During this period, you may feel hunger and cravings, but also more focus and mental clarity.
• Hour 24-36: After 24 hours, the body starts ketosis, where ketones become the main source of energy. Ketone levels keep rising, and you feel suppressed appetite as your body gets used to burning fat to provide energy. Also, during this period, autophagy is triggered.
• Hour 36-48: Ketone levels keep increasing, and fat is the only energy source for all bodily functions. You may also experience higher autophagy (but you won’t probably feel it, as it happens inside your cells!). You experience more stability in energy and mood as your body is more adapted to the fasting state. This is the time you need to drink enough water to avoid dehydration. 
• End of the Fast: When the 48 hours of fasting are finished, you can break the fast. But is it okay to start eating as you did before the fast? Can you eat and drink whatever you like? Is it safe? Let’s find out in the following section.

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

How to Do a 48-Hour Fast?

The most important point about breaking a 48-hour fast is starting with small, simple, and easily digestible meals to allow the digestive system to adapt. Here are the steps you need to take to break the fast healthily.

• Step 1: Consult a Healthcare Professional.

Whether or not you have underlying health concerns, it’s wise to consult a physician or dietitian and take the necessary tests to ensure a 48-hour fast is suitable for you. Sometimes, the doctor gives you specific orders for breaking the fast.

• Step 2: Choose a Start Date and Time.

Start and end your 48-hour fast at a specific time to make your mind ready and ensure you have enough time or planning.

• Step 3: Prepare 1-2 Days Before Fasting.

Before you start fasting, you need to prepare your body by decreasing calorie consumption, consuming nutritious, whole foods to provide essential vitamins and minerals, drinking enough water to avoid dehydration during fasting, and decreasing or avoiding caffeine intake to avoid caffeine withdrawal symptoms during fasting.

• Step 4: Plan the Meals Carefully.

Your last meal before the fast should be well-balanced to provide enough nutrients for the next 48 hours. You can break the fast with a simple, small, and easily digestible meal, like soup, salad, or lean protein and vegetables.

• Step 5: During the Fast (48 Hours)

Avoid calories during the 48-hour fasting. Drink plenty of water and other non-caloric drinks like black coffee and herbal tea. Avoid caloric beverages, including juices and sodas. Monitor your body’s signs and stop the fast if you feel severe discomfort, dizziness, or other adverse effects.

• Step 6: After the Fast Reintroduce Food Gradually.

Start with small, easily digestible meals containing nutritious foods like fruits, vegetables, lean proteins, and whole grains. Avoid overeating.

• Step 7: Adjust and Repeat.

After completing your first 48-hour fast, reflect on your experience and results, and based on your findings, try to adjust your method for the next fast to make the most of it. You can also consult experts and seek personalized guidance if needed.

I said the next fast, but the question is how fast you can have the next fast?! How frequently can you do a 48-hour fast? Scroll to find out!

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

How Often Should You Do a 48-Hour Fast?

Well, you’re the best person to decide the frequency of a 48-hour fast based on your goals, needs, your body’s reactions, and health status. However, considering the following points will help you decide more confidently.

• Consult a healthcare professional.
• Review your goals for trying fasting. Are you doing it to lose weight, gain metabolic health, autophagy, or other reasons? The frequency may change based on your answer to this question.
• Make informed decisions. If you’ve only heard about the positive effects of fasting and haven’t tried it yet. It’s better to start with shorter fasts to see how your body reacts. Monitor and keep the records. If things are fine, you can go for longer fasts. It’s easier for some people to try 48-hour fasting more frequently than others.
• Generally, it’s not common to do a 48-hour fast more than once a week. Then again, it depends on you, your body, and your goals. Anyhow, it’s good to give your body some days after the fast to get ready for the next round of fasting.
• Stay hydrated and choose nutritious meals before and after fasting to gain the necessary minerals, vitamins, and nutrients and keep your general health.
• Your current body composition and body fat percentage are also important as if you have higher body fat percentages, you may tolerate fasting more frequently, as you have more stored energy reserves.
• High levels of stress or inadequate sleep can affect your ability to fast comfortably, and you may need to have longer intervals between fasts.

Many expert fasters try a 48-hour fast once or twice a day. Of course, it’s not their lifestyle or long-term habit. They usually try this type of intermittent fasting to achieve specific short-term goals like weight loss.

Once a Week

Fasting for 48 hours once a week is common, but some people even do it once a month. It all depends on your choice and status.

Twice a Week

To achieve certain goals, some people try a 48-hour fast twice a week for a short time. However, it’s not recommended to try a 48-hour fast more than once a week unless you have tested everything and it is medically approved to be safe for you.

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

48-Hour Fast and Autophagy

Extended fasting, like a 48-hour fast, can trigger autophagy and maintain it. Autophagy, which means self-eating in Greek, is a cellular process to clean and recycle cells from damaged or dysfunctional cells and cellular components, including organelles and proteins, which helps cell rejuvenation. 

Autophagy can help cellular repair, increase longevity, and prevent diseases, including neurodegenerative conditions like Alzheimer's and Parkinson's disease.

How to Break a 48-Hour Fast?

• Start Slowly: Break your fast with simple, low-fiber meals, like fruits, vegetables, lean proteins, and carbohydrates that are easy to digest.
• Hydrate First: When breaking the fast, drink a glass of water before eating foods to rehydrate your body. Herbal tea or diluted fruit juice is also good.
• Chew Completely: Chew your food slowly and thoroughly to help digestion. It also helps prevent bloating and discomfort.
• Avoid Overeating: Listen to your body’s hunger and fullness signals and avoid overeating to let your body adapt.
• Avoid Overly Processed Foods: Break the fast with nutritious, whole foods to nourish your body properly.

In addition to the above general guidelines, you need to know what foods you can eat and avoid after a 48-hour fast for optimal health and the best results.

Foods to Eat after a 48-Hour Fast

• Fruits: Easily digestible fruits like watermelon, cantaloupe, or berries
• Vegetables: Steamed or lightly cooked vegetables like spinach, carrots, or zucchini
• Lean Proteins: Skinless chicken, turkey, or tofu
• Complex Carbohydrates: Whole grains like brown rice or quinoa
• Broths or Soups: Clear broths or simple vegetable soups
• Yogurt or Probiotics: Yogurt with live cultures or probiotic supplements
• Nuts and Seeds: Small servings of nuts and seeds in moderation

Foods to Avoid after a 48-Hour Fast

• Highly Processed or Fried Foods
• High-Fiber Foods: Initially, avoid high-fiber foods like whole grains, beans, and cruciferous vegetables.
• Fatty Cuts of Meat Initially
• Fatty Foods: Avoid foods high in saturated or trans fats.
• Caffeine and Alcohol: Skip caffeinated beverages and alcoholic drinks immediately after fasting, as they can be dehydrating.
• Spicy Foods
• Large Meals
• Sugary Foods

Now that we have learned the basic and essential points about the 48-hour fast, let’s read some pro tips for a healthy fast.

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

Pro Tips for a Healthy 48-Hour Fast

• Consult a Healthcare Professional: If you have certain medical conditions, take medications, or are pregnant or breastfeeding, consult with a healthcare specialist.
• Plan Your Fast: Prepare mentally and physically for your fast. Choose a time when you don’t have a lot of activities or social commitments. Let your family or friends know about your fasting plans for support.
• Stay Hydrated: Drink enough water during fasting to prevent dehydration. You can also drink herbal tea or black coffee.
• Balance Electrolytes: Add some salt to your water or drink an electrolyte solution to keep electrolyte balance during the fast, but don’t overdo it.
• Eat Mindfully Before and After Fasting: Eat nutritious foods, and gradually transition into and out of fasting with light, easily digestible meals.
• Listen to Your Body: Record your hunger cues, thirst, and overall well-being during fasting, and break the fast if you feel extreme discomfort, dizziness, or negative effects.
• Keep Busy and Distract Yourself: Do your favorite activities to keep your mind off the fast and hunger.
• Avoid Intense Exercise: While light physical activity like walking or gentle yoga is safe during a 48-hour fast, it’s better to avoid intense workouts to prevent fatigue and dehydration.
• Supplement Wisely: Consult with a healthcare specialist before taking any supplements during fasting.
• Track Your Progress: Keep a journal of your fasting experience, including how you feel, your symptoms, and general health, to understand your body's reactions to fasting.
• Practice Mindfulness: Try meditation or deep breathing to manage stress and stay in tune with your body during the fast.
• Maintain Social Support: Seek support from your friends or social media support groups for more encouragement.
• Break the Fast Gently: Break your fast with small, balanced meals to avoid digestive issues.
• Progress Gradually: If you're new to fasting, start with shorter fasting durations and gradually increase the period to reach the 48-hour fast to make sure it has no specific negative effects.

Is a 48-Hour Fast Healthy?

A 48-hour fast can be healthy if you follow the points and tips mentioned above and have it as part of a well-balanced and mindful approach to nutrition and well-being.

However, your individual health status, goals, and how you approach the fast can affect whether it’s good for you. Also, consulting a dietitian can help you decide with open eyes.

Who Should Avoid the 48-Hour Fast?

The following groups of individuals need to avoid fasting or be cautious and consult a healthcare professional before trying extended intermittent fasting like a 48-hour fast.

• Individuals with Certain Medical Conditions: If you have conditions affecting blood sugar regulation, cardiovascular health, kidney function, or liver function, consult with a healthcare expert first.
• Pregnant and Breastfeeding Women: Fasting during pregnancy or while breastfeeding can have negative nutritional effects on the mother and the developing or nursing child.
• Children and Adolescents: Extended fasting is generally not recommended for children and adolescents, as their bodies are still growing and developing.
• Those with Eating Disorders: Individuals with eating disorders, like anorexia nervosa or bulimia, should avoid any form of prolonged fasting.
• Individuals with Low Body Weight: If you’re underweight, you may be at higher risk of nutrient deficiencies and complications during fasting.
• Those Taking Specific Medications: Fasting can affect the absorption and effectiveness of some medications.
• Dehydration Prone Individuals: If you’re prone to dehydration or have conditions that increase the risk, such as kidney stones or a history of heat-related illnesses, you’d better avoid fasting.
• Athletes or Those Doing Heavy Physical Activity: Doing intense workouts while fasting can increase the risk of fatigue, dehydration, and other negative effects.
• First-Time Fasters: If you are new to fasting, it’s better to start with shorter fasts, like 8- or 12-hour fasting, to see how your body reacts.
• Those with Psychological Health Concerns: Fasting can affect mood and mental well-being and may not be suitable for everyone.

Diarrhea after a 48-Hour Fast

Experiencing diarrhea after a 48-hour fast can happen in some individuals as the body tries to adapt to the new eating situation. Diarrhea can happen after a 48-hour fast for different reasons, including

• Eating too much food too fast,
• Consuming fiber quickly after a 48-hour fast,
• Being allergic to some foods,
• Bacterial imbalance,
• Dehydration,
• Stress, or anxiety.

Summary

A 48-hour fast can be a useful approach to lose weight and gain health benefits. However, you must first check if your body can tolerate prolonged fasting. You can start with less challenging types of intermittent fasting and then extend the fasting period.

FAQ

The following subsections answer the most frequently asked questions about a 48-hour fast.

How Much Weight Can You Lose on a 48-Hour Fast?

Your body's metabolic status, activity level, and eating habits define how much weight you can lose on a 48-hour fast. But most individuals lose about four to six pounds during a 48-hour fast.

Does a 48-Hour Fast Burn Belly Fat?

Yes, a 48-hour fast can generally help you lose body fat and weight due to the caloric deficit it creates.

Is a 48-Hour Fast Long Enough for Autophagy?

Yes, autophagy can start after 24 hours and deepen after 48 hours of fasting.

What Is the Best Time of the Week to Fast for 48 Hours?

There’s no specific time for a 48-hour fast; you can choose the best time based on your goals, plans, and schedule.

Can Everyone Do a 48-Hour Fast?

Yes, but people with type 1 diabetes, those with eating disorders, and pregnant or breastfeeding women need medical supervision.

Is a 48-Hour Fast Different from Intermittent Fasting?

A 48-hour fast is an extended type of intermittent fasting.