Intermittent fasting is an eating pattern that alternates between periods of fasting and eating.

It has gained popularity in recent years and is linked to health benefits like increased insulin sensitivity, cellular repair, and weight loss (1, 2, 3).

While shorter-duration fasts tend to be more common, some people prefer to fast for longer periods.

A 48-hour fast is the longest duration commonly practiced with intermittent fasting. Despite the noted benefits, you should take its drawbacks into consideration.

This article explains all you need to know about 48-hour fasting, including how to do it and its benefits and downsides.

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In theory, a 48-hour fast is simple — you merely give yourself a full, two-day break from eating. One common method is to stop after dinner on the first day and begin eating again at dinnertime on the third.

Contrary to popular belief, you can still drink zero-calorie fluids, such as water, black coffee, and tea, during the fasting period.

It’s vital to drink plenty of fluids to prevent dehydration, which is one of the major potential complications of longer fasts (4).

Afterward, it’s important to gradually reintroduce food. That way, you avoid overstimulating your gut, which may lead to bloating, nausea, and diarrhea (5).

Your first meal post-fast should be a light snack, such as a handful or two of almonds. This would be followed by a small meal one or two hours later.

On non-fasting days, you would maintain your usual eating pattern, making sure to refrain from overindulging in higher-calorie foods.

It’s most common to do a 48-hour fast 1–2 times per month as opposed to once or twice per week, as required by other fasting methods. Appropriately spacing out your 48-hour fasts may offer greater health benefits (1, 2, 3).

As 48-hour fasting is not advisable for everyone, you should try shorter fasts, such as the 16:8 or alternate-day methods, before doing a 2-day session. This will help you understand how your body responds to a lack of food.

Summary A 48-hour fast involves abstaining from eating for 2 consecutive days, usually done once or twice per month. It’s important to drink plenty of fluids during the fast and slowly reintroduce food afterward.

Although the health benefits of intermittent fasting are well documented, specific research on 48-hour fasting is limited.

That said, several studies examine prolonged fasting, which is defined as more than 24 hours (6).

May slow cell aging

Cellular repair is your body’s natural way of replenishing its cells. It may help prevent disease and even delay tissue aging (7, 8).

Improved cellular repair and delayed tissue aging have been shown to support overall longevity, though this research is mostly limited to animal studies (9).

Still, many studies indicate that 48-hour fasting can improve cellular repair more than other fasting methods (1, 10).

May reduce inflammation

Temporary inflammation is a normal immune response, but chronic inflammation can have serious health consequences, such as cancer, heart disease, and rheumatoid arthritis (11).

Fasting for more than 24 hours may lower inflammation by reducing oxidative stress in your body’s cells (2).

Improves insulin sensitivity and blood sugar levels

Insulin serves as the storage hormone for carbs, protein, and fats. Carbs and fats are your body’s preferred source of energy.

During a fast of 24 or more hours, glycogen — the storage form of carbs — is depleted and insulin levels are reduced. This allows your body to burn mostly fat for energy, making stored body fat more available for use (3, 12, 13).

Many studies note that various types of fasting, including 48-hour fasting, may decrease insulin levels. What’s more, they improve insulin sensitivity, which allows your body to transport blood sugar more efficiently (14).

One study in 10 people with type 2 diabetes found that 12–72-hour fasting decreased fasting blood sugar levels by up to 20% after a single fast (15).

Lastly, fasts lasting longer than 24 hours may have additional benefits for blood sugar control beyond those linked to shorter fasts (16).

May aid weight loss

Intermittent fasting may boost weight loss, though studies on 48-hour fasts specifically are lacking (17, 18, 19).

A 48-hour fast once or twice per month will reduce your calorie intake by up to 8,000 calories per month, which can promote weight loss.

Just make sure you don’t overcompensate for these lost calories during your periods of eating.

Still, fasting has been shown to increase metabolic rate by 3.6–14%, which translates to an additional 100–275 calories burned daily. This effect seems to diminish if you’re fasting longer than 72 hours (20, 21).

As 48-hour fasts should only be done 1–2 times per month, they may be best for individuals who would prefer to fast less frequently but still want to lose weight.

Summary Fasting for 48 hours may boost your health by promoting weight loss, improving insulin sensitivity, and reducing inflammation. It may also help you live longer by delaying cell aging.

It’s also important to be aware of the downsides of a 48-hour fast.

This duration is not suitable for everyone. The longer the fast, the greater the potential for side effects.

If you feel unwell, it’s always ok to stop fasting.

Hunger and dizziness

The main drawback of 48-hour fasting is severe hunger, although many people claim that this feeling is temporary.

In one study in 768 people fasting for at least 48 hours, 72% of participants experienced side effects, including hunger, fatigue, insomnia, and dizziness.

Therefore, it’s important to work your way up to a longer fast, starting with shorter durations. Always proceed with caution while fasting (22).

Exhaustion and sluggishness

While fasting, stored carbs drop after 24 hours, prompting your body to burn fat for energy.

As such, you may feel sluggish after the first 24 hours, especially if this is your first time trying a longer fast (3, 12, 13).

Due to its duration, a 48-hour fast may be more difficult to stick to than other fasting methods. You may want to start with a shorter fast, especially if you’re concerned about exhaustion (19, 23).

May interfere with social eating

Any type of fasting can interfere with social eating, such as going out for meals with friends or dining with your family on holidays.

Food plays a major role in many cultural practices, so you should consider whether you’re willing to curtail your social eating to fast.

That said, social eating may not be as big of a factor if you stick to the recommended 1–2 fasts per month for 48-hour fasting, as this is less of a time commitment than that of other fasting methods.

At-risk populations

While fasting may benefit your health in general, it is not for everyone.

Those with certain medical conditions should consult their medical practitioner before fasting, while others should not fast at all.

Several populations should not engage in a 48-hour fast, including (24):

  • people with type 1 diabetes
  • people with low blood pressure
  • those who are underweight or have a history of eating disorders
  • women who are pregnant, breastfeeding, trying to conceive, or have a history of amenorrhea
  • those taking certain medications, such as insulin, blood pressure, blood thinners, and nonsteroidal anti-inflammatory drugs (NSAIDS)

If you’re taking any medications, make sure to check with your healthcare practitioner before starting a fast.

Summary The main drawbacks of 48-hour fasting are hunger and fatigue. This practice may not be appropriate for people with type 1 diabetes, those with a history of eating disorders, or women who are pregnant or breastfeeding.

Several common fasting side effects can be prevented with proper strategies.

Fasting for extended periods can lead to dehydration if you don’t drink enough fluids and consume electrolytes.

Sodium, magnesium, potassium, and calcium are essential electrolytes that can be quickly depleted if you’re abstaining from food. Therefore, it’s best to supplement with these nutrients if you’re fasting for longer than 24 hours (25).

Here are a few methods to prevent complications during your fast (26):

  1. Stay hydrated by drinking water with a pinch of salt or electrolyte tablets, which you can easily buy online.
  2. Drink black coffee or green tea to help reduce hunger levels.
  3. Flavored, non-calorie sparkling water can also be a great hydration option.
  4. Keep your mind busy to prevent obsession with hunger. Distractions may include taking a walk, watching a movie, reading a book, or listening to a podcast.
Summary It’s necessary to drink plenty of fluids during a 48-hour fast to stay hydrated. Keeping your mind busy can also stop you from obsessing over hunger.

A 48-hour fast may provide several benefits, including enhanced cell repair, weight loss, and insulin sensitivity.

However, as there are many ways to do intermittent fasting, some may work better for you than others. It's recommended that you try shorter fasts first to avoid any serious side effects.

Overall, if you approach fasting carefully and methodically, it can become an integral part of your wellness routine.