What Happens At 48 Hours Of Fasting

Written by Andrew Brewer. ⚕️Reviewed and fact checked by our medical team.

What Happens At 48 Hours Of FastingProlonged fasts aren’t for the faint of heart, but if you’re able to complete one, you’ll experience a lot of benefits. A lot of the magic starts during a 48-hour fast, and here’s what you can expect. Spoiler alert, it may not seem like it at the time, but afterward, you’ll feel like a brand-new person!

Key Takeaways

  • A 48-hour fast is a type of intermittent fasting where you abstain from eating for two consecutive days. This fasting period triggers ketosis and autophagy in the body.
  • Ketosis is a metabolic state in which the body burns fat for energy when it has depleted its glucose stores. It can be achieved after approximately 12 hours of fasting and promotes weight loss and various health benefits.
  • Autophagy is a cellular process in which the body eliminates damaged or dead cells and replaces them with healthy cells. It can occur after 18 hours of fasting and helps cleanse the body of toxins, reducing the risk of diseases.
  • Both ketosis and autophagy have numerous health benefits, including weight loss, reduced risk of heart disease, type 2 diabetes, dementia, and inflammation. They can also improve cellular health and may lower high blood pressure.
  • It is important to consult with a doctor before attempting a prolonged fast, especially if you have any pre-existing medical conditions. Prolonged fasts should generally be undertaken only once or twice a month and can be combined with other forms of intermittent fasting for optimal results.

What is a 48-hour Fast?

A 48-hour fast is a type of intermittent fasting where you don’t eat for two days. If you start your fast at 9 a.m. on Monday, you would not eat again until 9 a.m. on Wednesday. During this time, your body undergoes different processes to help sustain it during this fasting window.

  • Ketosis, which is when your body burns fat stores after it burns through all available glucose.
  • Autophagy, which is when your body starts to purge dead or damaged cells, replacing them with new healthy cells.

These two processes will help you lose weight and feel better while doing it, which is a great side effect of intermittent fasting for 48 hours.

Ketosis and Intermittent Fasting

Your body can enter into ketosis after just 12 hours, just as long as it’s worked through the calories you had consumed previously. Once there is no more food and glucose to burn through, it will turn to other energy resources in the body, namely fat.

Prolonged fasts trigger ketosis in the body, but it is critical that you do not consume any calories lest you kick your body out of ketosis. Even no-calorie sweeteners can cause you to leave ketosis, so tread lightly as you add these to your black coffee or tea.

Ketosis is an ideal state to promote weight loss, but it can also help reduce the risk for heart disease, type 2 diabetes, dementia, and more. It can even reduce inflammation in the body and high blood pressure, so if you can promote ketosis in your body, you will notice an overall improvement in your health, especially if you have been at risk for developing these conditions.

Autophagy and Intermittent Fasting

Autophagy is an internal process that promotes healthy cellular development. There can be any number of reasons why cells break down and become damaged and, in some cases, dead. However, the body doesn’t always purge them right away; instead, they can stay in the body, causing reduced function and, in some cases, diseases.

Autophagy will help your body get rid of those bad cells, cleansing the body of toxins. These cells are replaced by healthy cells, which can reduce the risk of developing diseases, cancer, and more. Much like ketosis, you want your body to go through autophagy during intermittent fasting to get the most benefits.

Your body can enter into autophagy as soon as 18 hours after fasting or up to four days. The more consistent you can be with your fasting, the more likely it will be that your body will enter into this state. You do not need to be in ketosis to be in autophagy.

So, What Happens to Your Body During a 48-hour Fast?

48-hour fasts are incredibly powerful to promote weight loss, as well as improve your overall health and well-being. This is because your body can enter into two very important processes: ketosis and autophagy. Together, you will burn fat while purging your body of harmful toxins.

This prolonged fast should only be undertaken one to two times a month, and it can be used in conjunction with other intermittent fasts for the best results. Check with your doctor before you undertake a prolonged fast to ensure it won’t interfere with any pre-existing conditions.


  • Is it safe to fast for 48 hours?

Fasting for 48 hours can be safe for most healthy individuals, but it is important to consult with your doctor before attempting a prolonged fast, especially if you have any pre-existing medical conditions.

  • Can I drink water during a 48-hour fast?

Yes, staying hydrated is crucial during fasting. You can and should drink water and other non-caloric beverages like black coffee or tea to maintain hydration.

  • Will I feel hungry during a 48-hour fast?

It is normal to experience hunger during a fast, especially in the initial stages. However, hunger pangs usually subside after the first day as your body adjusts to the fasting state.

  • Can I exercise during a 48-hour fast?

Light to moderate exercise is generally safe during a 48-hour fast. However, intense or strenuous exercise may be challenging due to reduced energy levels. Listen to your body and adjust your activity level accordingly.

  • Can I take medications or supplements during a 48-hour fast?

It is important to follow your doctor’s guidance regarding medications and supplements during fasting. Some medications may need to be taken with food, so consult your healthcare provider to determine the best approach.

  • Will fasting for 48 hours help me lose weight?

Yes, fasting for 48 hours can promote weight loss as it triggers ketosis, where the body burns fat for energy. However, sustainable weight loss requires a combination of healthy eating habits and regular physical activity.

  • How often should I undertake a 48-hour fast?

It is generally recommended to limit 48-hour fasts to once or twice a month. Fasting too frequently or for prolonged periods may have adverse effects on your overall health.

  • Can I continue intermittent fasting after completing a 48-hour fast?

Yes, you can incorporate intermittent fasting into your regular routine even after completing a 48-hour fast. However, it’s essential to find a fasting pattern that suits your individual needs and consult with a healthcare professional if necessary.

  • Are there any risks associated with a 48-hour fast?

While fasting has potential health benefits, there can be risks for certain individuals, such as those with underlying medical conditions. It is crucial to consult with your doctor to ensure that a prolonged fast won’t interfere with your health or any existing conditions.

  • Can I consume any calories or sweeteners during a 48-hour fast?

To maintain the benefits of fasting, it is generally recommended to consume no calories during the fasting period, including no-calorie sweeteners. Even small amounts of calories or sweeteners can disrupt the fasting state and hinder the desired effects of ketosis and autophagy.

Andrew Brewer

Andrew Brewer

Andrew Brewer started Fastingapps.com to give people the guidance that he never received when he was first starting. His goal is to make your goals achievable and to offer you only the best fasting apps that the internet has to offer. You're not on your own - Andrew and the entire family of reviewers at Fastingapps.com are here with you every step of the way!