48-Hour Fast: Benefits, Side Effects, and How-to 

A 48-hour fast is an extended intermittent fasting that aims to improve overall health by resetting the body. In this comprehensive article, we will cover the benefits, drawbacks, and how to minimize them, and tips on what to do during fasting and how to break it.

Key Takeaways: 

  • The 48-hour fast allows any non-caloric drink during the fasting period. The prolonged fasting activates autophagy and ketosis. 
  • Benefits include cellular repair, weight loss, cognitive function, reduced inflammation, improved blood sugar and lipid levels, digestion, stabilized energy levels, and improved mood.
  • Possible drawbacks include hypoglycemia symptoms, including dizziness, hunger, and fatigue, possible muscle loss, and may not be suitable for certain populations, including those with eating disorders.
  • Proper hydration and electrolyte supplementation help mitigate the side effects, and the best way to break a fast is by slowly introducing solid foods to help the digestive system readjust. 
  • It’s safe to start 48-hour fasting once a month and increase it to twice once the body fully adapts to the frequency.

Table of Contents:

What Is a 48-Hour Fast?

A 48-hour means abstaining from calorie intake, spanning two consecutive days.

Unlike shorter fasting windows, such as 16/8 intermittent fasting (16 hours fasting, 8 hours eating) or 24-hour fasting, a 48-hour fast requires sustained commitment and discipline.

During the fasting period, one can have water or unsweetened tea or coffee, and other non-caloric drinks but nothing with calories in them. 

During this fasting period, the body enters a unique metabolic state.1 This state involves the depletion of glycogen stores, leading to ketosis, where the body uses stored fat for energy.2

A 48-hour fast triggers specific physiological responses, including the activation of autophagy, a cellular process where the body cleans out damaged cells and regenerates new, healthy ones. 

Health Benefits of a 48-Hour Fast

48-hour fast

1. Encourages Cellular Repair

Studies have proven that a 48-hour fast triggers autophagy,3 a cellular process of removing damaged or dysfunctional cellular components. This meticulous cleaning process promotes cellular repair, optimizing cellular function and longevity.

Some studies also support that 48-hour fasting is more effective in activating autophagy than other fasting methods.

2. Boost Weight Loss

The extended duration of a 48-hour fast induces a significant calorie deficit, prompting the body to utilize stored fat for energy, resulting in weight loss. 

Intermittent fasting is a well-established method for weight loss. In a 2022 study, intermittent fasting was found to be effective in reducing body weight,4 waist circumference, and fat mass without affecting lean mass. 

The same study also concluded that calorie restriction, which happens in a 48-hour fast, was more effective in weight loss. These results show that doing the 48-hour fast has a synergistic effect on weight management. 

3. Enhance Cognitive Function

While the mechanism remains unclear, intermittent fasting has been shown to have neuroprotective effects.5 Moreover, studies also suggest that intermittent fasting enhances cellular stress resistance, synaptic plasticity, and neurogenesis.6

These data suggest that 48-hour fasting has the potential to enhance cognitive functions and aid in preventing neuronal aging, which plays a major role in neurodegenerative diseases. 

This claim is backed by studies on intermittent fasting’s ability to delay or reverse Alzheimer’s disease7 and Parkinson’s disease.8

4. Helps Reduce Inflammation

Intermittent fasting has been established to modulate inflammation. In a study of 8-week intermittent fasting,9 subjects showed reduced inflammatory markers such as CRP and calprotectin and were seizure-free throughout the intermittent fasting duration. 

Other studies also support intermittent fasting’s ability to modulate immune cells and cytokines,10 preventing unnecessary inflammation. 

5. Improves Blood Sugar Levels

Due to the lack of calorie intake, intermittent fasting methods such as 48-hour fasting decreases blood sugar levels. 

In a 2022 study, intermittent fasting reduced fasting blood glucose, HbA1c, and plasma insulin levels11 along with decreased body weight, waist circumference, and BMI. The same study also reports improved insulin sensitivity among its subjects.

Due to its ability to lower blood glucose levels, 48-hour fasting has been used to diagnose insulinoma,12 a tumor in the pancreas that causes abnormal increases in insulin levels.13

6. Improves Digestion

Studies have shown that intermittent fasting such as the 48-hour fast decreases harmful gut bacteria and improves fecal bacterial diversity, leading to a healthier gut and improved digestion.14

This effect leads to a healthier metabolism, which is crucial for weight loss and metabolic health.  

7. Boosts Cardiovascular Health

A 48-hour fast boosts cardiovascular health by regulating blood lipid levels and improving blood pressure. A 6-week study on intermittent fasting resulted in decreased LDL levels and improved HDL levels.15

In another study, intermittent fasting resulted in decreased total cholesterol and triglyceride levels.11 Moreover, a study comparing pre and post-IF blood pressures revealed that post-IF blood pressure readings were much lower than pre-IF readings.16

8. Stabilizes Energy Levels

While fatigue may be experienced in the initial phase of intermittent fasting, your body adapts to the metabolic shift and uses fat as a more stable energy source in prolonged fasting periods. 

In a 2022 study of 12-week intermittent fasting, subjects did not report increased hunger17 throughout the duration and were able to tolerate the fasting periods well. 

9. Releases Growth Hormone

Intermittent fasting’s ability to increase growth hormone (GH) release has been established since the 19th century. Older studies have proven intermittent fasting’s ability to increase the frequency and amplitude of GH.18 

10. Improves Mood

Despite the lack of food intake, intermittent fasting’s ability to stabilize cognitive function positively impacts mood. Studies show that intermittent fasting decreases anxiety and depression19 rates without causing fatigue. 

Potential Side Effects

1. Hunger and Dizziness

Hunger and occasional dizziness are common side effects20 during a 48-hour fast, particularly for individuals new to extended fasting. This happens when the body experiences hypoglycemia or dehydration.

2. Fatigue and Sluggishness

Hydration is crucial when fasting. While drinking water is allowed during fasting periods, some people don’t meet the required amount of water to prevent dehydration, causing fatigue and sluggishness. 

3. Possible Hypoglycemia

During the initial phase, you may experience hypoglycemia21 due to the decrease in blood glucose levels and glycogen stores, especially when you’re new to fasting. Symptoms may include shaking or jittering, hunger, fatigue, confusion, or irritability.

4. Increases Risks of Binge Eating

People with a history of eating disorders need professional guidance before doing prolonged fasting as the 48-hour fast. There has been evidence that intermittent fasting may increase the risks of binge eating.22 

5. Not For Everyone

People who have specialized diets should not attempt the 48-hour fast without medical advice. Some populations, including children, pregnant and lactating women, and those with underlying medical conditions should do this under medical supervision.

How to Minimize Side Effects

If you’re a beginner, doing a 48-hour fast may be challenging. Here are easy steps to follow to minimize side effects:

  1. Stay Hydrated: Adequate hydration is crucial during fasting to help alleviate feelings of hunger and dizziness. Hydration also contributes to a sense of fullness, aiding in appetite control.
  2. Consume Electrolytes: Electrolytes play a vital role in maintaining proper muscle function and hydration levels, addressing imbalances that may arise during a 48-hour fast.
  3. Gradual Adaptation: Gradually increasing fasting durations allows the body to adapt to the metabolic and physiological changes associated with extended fasting. 

What to Do During a 48-Hour Fast

While fasting, consider incorporating the following practices to enhance the experience and support overall well-being:

  • Low-Intensity Activities: Engaging in low-intensity activities, such as walking or gentle stretching, can help distract from feelings of hunger and promote a sense of well-being during a 48-hour fast.
  • Stay Hydrated: Continue to prioritize hydration throughout the fasting period. Herbal teas or plain water can be consumed to maintain fluid balance.
  • Listen to Your Body: Pay attention to your body’s signals. If feelings of fatigue or dizziness become pronounced, consider adjusting activity levels or breaking the fast if necessary.

How to Break a 48-Hour Fast

Breaking a 48-hour fast requires a gradual and mindful approach to reintroduce nutrients to the digestive system. Consider the following steps:

  1. Start with Fluids: Begin by hydrating with water, herbal teas, or clear broths. This helps prepare the digestive system for the reintroduction of solid foods.
  2. Include Easily Digestible Foods: Opt for easily digestible foods such as soups, fruits, vegetables, and lean proteins. These choices minimize the digestive burden after a period of fasting.
  3. Avoid Heavy or Processed Foods: Steer clear of heavy or processed foods initially. These may be harder for the digestive system to process after a prolonged fast.
  4. Monitor Portion Sizes: Be mindful of portion sizes to prevent overeating. Start with smaller servings and gradually increase as the digestive system adjusts.

How Often Should You Do a 48-Hour Fast?

For beginners once a month is a good start. You can increase it to twice monthly once you build tolerance.

The frequency of 48-hour fasts depends on individual goals, health status, and tolerance.

However, it’s crucial to listen to your body, adjust frequency as needed, and consult a healthcare professional when necessary. 

Is a 48-Hour Fast Safe?

When approached responsibly, a 48-hour fast can be safe for many individuals. However, certain populations, such as pregnant or breastfeeding women, individuals with a history of eating disorders, or those with specific medical conditions, should exercise caution.

Frequently Asked Questions

Does fasting for 48 hours do anything?

Fasting for 48 hours will improve blood pressure levels and lessen weight due to water loss. However, when done more regularly, it may aid in weight loss, improving metabolic health, and enhancing cognitive functions.

How much weight can you lose in a 48-hour fast?

Most people lose up to 4 pounds after a 48-hour fast. However, this depends on one’s metabolic rate and activity throughout the fasting period.

Will a 48-hour fast put me in ketosis?

Yes, fasting for a minimum of 16 hours will put your body in a state of ketosis where the body uses fat as the energy source. 

Is 48 hours enough for autophagy?

Yes, studies have shown that a 48-hour fast is more effective in activating autophagy than other intermittent fasting methods. 


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2Dhillon KK, Gupta S. Biochemistry, Ketogenesis. [Updated 2023 Feb 6]. In: StatPearls [Internet]. Treasure Island (FL): StatPearls Publishing; 2024 Jan-. Available from: https://www.ncbi.nlm.nih.gov/books/NBK493179/

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9Roco-Videla, Á., Villota-Arcos, C., Pino-Astorga, C., Mendoza-Puga, D., Bittner-Ortega, M., & Corbeaux-Ascui, T. (2023). Intermittent Fasting and Reduction of Inflammatory Response in a Patient with Ulcerative Colitis. Medicina, 59(8). https://doi.org/10.3390/medicina59081453

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Mag. Stephan Lederer, MSc. is an author and blogger from Austria who writes in-depth content about health and nutrition. His book series on Interval Fasting landed #1 on the bestseller list in the German Amazon marketplace in 15 categories.

Stephan is a true man of science, having earned multiple diplomas and master's degrees in various fields. He has made it his mission to bridge the gap between conventional wisdom and scientific knowledge. He precisely reviews the content and sources of this blog for currency and accuracy.

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