A 48-hour fast is a form of intermittent fasting that involves taking a 2-day pause on eating while drinking only calorie-free fluids. A 48-hour fast may not be suitable for everyone, as it carries certain risks for some groups of people.

Intermittent fasting as a whole has gained popularity recently due to the potential health benefits of the practice. A 48-hour fast is one of the longest fasting durations, with shorter fasting periods being more common.

In this article, we discuss how to perform a 48-hour fast and the potential risks and benefits. We also provide some tips that may help make the fasting period a smoother experience.

A person doing a 48 hour fast holds a glass of water.Share on Pinterest
People can only consume calorie-free drinks, including water, black coffee, and herbal tea, during a 48-hour fast.

Intermittent fasting involves rotating between periods of eating and fasting to give the body — in particular, the digestive system — a rest.

During this time, the body creates energy from stored fuel sources.

A 48-hour fast is an extended form of intermittent fasting. It involves not consuming any calories for a full 2 days.

While the fast involves eliminating foods that contain calories, it is still important to drink plenty of noncaloric fluids, such as water, throughout the fast to keep the body hydrated.

Some people may use a 48-hour fast to reduce their calorie intake and help them lose weight. Others may use the fast to support digestive health.

While taking a 2-day break from eating seems daunting at first, this method typically makes use of the body’s natural rhythms to make the fast more manageable.

A simple 48-hour fast will use the body’s sleep schedule to cut into that time.

As an example, for a fast starting on Monday, the person would stop eating in the evening on that day. They would then start eating again in the evening on Wednesday.

Using this method, the person will give their body time to digest their last meal on Monday before they sleep. By the time they wake up on Tuesday, about 10–12 hours of their fast has already passed.

The person then spends Tuesday and Wednesday drinking only calorie-free fluids, such as water, herbal tea, and black coffee.

When Wednesday evening comes, the person has a light, simple dinner. From Thursday onward, they can gradually reintroduce their regular diet.

Hydration is one of the most important aspects of any fast. Fluids keep the body and cells hydrated, as well as helping eliminate waste. It is important that people avoid dehydration during a fast by ensuring that they drink plenty of fluids.

It may also be advisable for people to try other, less extreme versions of intermittent fasting before attempting the 48-hour fast. One such version is the 16:8 method, which involves consuming all food within an 8-hour window and then consuming only calorie-free beverages for the next 16 hours.

Starting with shorter fasts will help a person prepare for longer ones and get an idea of how their body will respond.

A 48-hour fast can serve as a reset for the body, allowing it to take a break from digestion to focus on other tasks. This break may allow it to focus energy elsewhere, such as on repairing the body.

According to the authors of a 2014 article, fasting may reduce obesity, hypertension, asthma, and rheumatoid arthritis.

A study featuring in Obesity notes that regular intermittent fasting offers many benefits for the body, including:

  • improved brain function
  • reduced blood pressure and heart rate
  • reduced inflammation
  • increased insulin sensitivity
  • enhanced digestion
  • reduced glucose levels
  • reduced markers of oxidation and stress

The researchers suggest that many of these benefits are due to the influence of weight loss.

Autophagy

The concept of autophagy is also popular with proponents of intermittent fasting. In the simplest terms, this is the process of the body removing parts of cells that are no longer functioning as they should.

By recycling or disposing of damaged cell material, autophagy allows the tissues to regenerate. The depletion of energy stores, which occurs during extended fasting, activates certain pathways that trigger autophagy.

A 2018 review states that fasting and calorie restriction are both ways to trigger autophagy in the cells of the body. Slowing down the digestive process allows the cells to focus on self-regeneration.

Weight loss

A 48-hour fast represents a large chunk of calorie deficiency in the diet, which can aid long-term weight loss in some people. However, a person should not perform 48-hour fasts too often.

A review article in Behavioral Sciences reports that intermittent fasting produces similar short-term weight loss results as traditional continuous calorie restriction in people with overweight and obesity. Therefore, cutting excess calories from the diet may be just as effective as fasting for weight loss.

As part of a regular intermittent fasting program or healthful weight loss regimen, a 48-hour fast may help a person reach their long-term weight loss goals, as long as they do it in a safe way.

With that said, no fast will replace diet and lifestyle choices, such as regular exercise and a balanced, nutritious diet, to support a moderate weight.

Learn more about intermittent fasting and exercise.

Side effects are common with longer fasts, such as a 48-hour fast, which is why it is important to try a smaller fast first to see how the body responds. If a person feels unwell, they should stop fasting.

Common side effects during longer fasts may include:

  • hunger and hunger pangs
  • digestive issues
  • fatigue
  • dizziness
  • irritability
  • insomnia or waking up frequently in the middle of the night
  • nausea
  • headaches
  • fainting

Additionally, it is important to reintroduce foods slowly. Overstimulating the digestive system by eating a big or heavy meal after a fast may cause its own side effects, such as:

Fasting may also affect people with underlying conditions differently. People with diabetes who take insulin or are on blood sugar-lowering medications will need to check with their doctor before engaging in any type of fasting, as fasting can drastically change how some medicines and insulin work.

Additionally, some people should avoid fasting altogether. Pregnant or breastfeeding women and people who have underweight or an eating disorder should not fast.

People who take certain medications alongside food may also need to avoid fasting. These medications include nonsteroidal anti-inflammatory drugs (NSAIDs), blood pressure medications, and blood thinners.

There are some general safety tips to keep in mind while fasting:

  • Hydration: It is very important to drink fluids and maintain hydration.
  • Drinking electrolytes: While some spring water contains natural mineral salts, it may be helpful to use electrolyte tabs or salts to add minerals to other water.
  • Expect cravings: The body will naturally have hunger pangs and cravings while fasting, sometimes in the middle of the night. Be prepared for these and the willpower that it takes to avoid eating and complete the fast.
  • Listen to the body: Strong side effects, such as dizziness, exhaustion, and fatigue, may indicate that a long fast is too much.
  • Reintroduce food slowly: After a long fast, it may be a good idea to have a small, simple snack before the first proper meal. Examples include a small bowl of rice, a piece of baked chicken, a boiled potato, or a small bowl of broth-based soup.

Intermittent fasting may provide the body with some benefits, such as giving the cells more time to repair and reducing inflammation. However, a 48-hour fast is a rather long fasting period, and it is not for everyone.

People who work long hours or have underlying conditions may have trouble with a 48-hour fasting period and should talk to a doctor before attempting it.