48 VS 72 Hour Fast

48 VS 72 Hour Fast

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

48 VS 72 Hour FastWith so many different intermittent fasting plans out there, it can be difficult to know which one to choose. Once you are more seasoned, you may even start wanting to dip your toes into the more advanced fasting, like 48 hours or even 72 hours. These plans may seem extreme, but there are benefits to prolonged fasts that you can’t get in shorter windows.

Let’s explore 48-hour vs. 72-hour fasts to help you decide which one is right for you.

Key Takeaways

  • Prolonged fasting, such as 48-hour or 72-hour fasts, can provide benefits that shorter fasting windows may not offer.
  • During a fast, the body transitions from using glucose as an energy source to burning fat stores, a state known as ketosis, which can aid in weight loss.
  • Both 48-hour and 72-hour fasts stimulate autophagy, a process in which the body cleanses itself of damaged cells, potentially reducing the risk of diseases and improving overall health.
  • A 72-hour fast has additional benefits compared to a 48-hour fast, including increased cellular regeneration, improved insulin levels, and reduced oxidative stress, which can enhance brain function and decrease the risk of conditions like Alzheimer’s.
  • The choice between a 48-hour or 72-hour fast depends on individual preferences and goals. If seeking more extensive cellular repair and health improvements, a 72-hour fast may be more suitable, but starting with a 48-hour fast can serve as a stepping stone. Consulting a doctor before attempting prolonged fasting is recommended to address any questions or concerns.

What is a Prolonged Fast?

Sometimes called extended fasting, a prolonged fast is any type of fasting period that lasts more than 24 hours. This could be a 48-hour fast, where you don’t eat for two days, or it could be a 72-hour fast, where you don’t eat for three days. There are fasts that can extend longer than these periods; however, you should not participate in one without guidance from a medical professional.

What Happens in a 48-hour Fast?

Before your body moves to the fat stores and starts other regenerative processes, it needs to work through the calories you’ve eaten. It typically takes about 12 hours to work through that, though it can vary based on the amount of food you’ve eaten.

Once it has no more food to convert, it will start to move from glucose as an energy source to burn fat stores. This is called ketosis, and it is a great way to trigger weight loss, among other benefits. If you consume any calories, no matter how small, you will kick your body out of ketosis, which is why it’s critical to stick strictly to fasting without cheating.

Keep in mind that some no-calorie sweeteners can trigger a metabolic response even if they don’t have calories, which can kick your body out of ketosis. When this happens, you will need to start the process all over.

Between 24 and 48 hours, your body will also begin autophagy, which is when your body starts to cleanse itself of damaged cells. As it rids itself of toxins, only healthy cells remain, which is why fasting can help reduce the risk of diseases and illnesses.

What Happens in a 72-hour Fast?

All of the benefits of a 48-hour fast are compounded in a 72-hour fast. Your body will enter autophagy and ketosis, helping to level out your body’s insulin levels.

During the 72-hour fast, your body will start to produce new stem and immune system cells, as well as reduce the oxidative stress in your body. The new cells that are produced are healthy as your body is in the process of autophagy. 72-hour fasting can also improve your brain function, reducing the risk of Alzheimer’s.

Ultimately, your body regenerates more cells during a 72-hour fast, so if you’re looking to improve your overall health, you may want to look into longer fasting. The longer you fast, the more benefits you get.

Which is Better for You: 48-hour or 72-hour Fasting?

Which fast you choose is up to you. Both will give fantastic benefits, helping you lose weight, improve your health, and reduce the risk of diseases. The most important processes – autophagy and ketosis – take place in both of these fasts, so you will feel better after, even if it doesn’t feel like it at the time.

If you want more cellular repair, then a 72-hour fast will be better for you. However, if that feels too challenging, you can always ramp up to it by doing a 48-hour fast first. If you have any questions or concerns, consult with a doctor before starting either of these prolonged fasts.


  • Is it safe to engage in prolonged fasting for 48 or 72 hours?

Prolonged fasting should be approached with caution. While 48 and 72-hour fasts can be safe for many individuals, it is important to consult with a medical professional before starting any extended fasting regimen, especially if you have any underlying health conditions or concerns.

  • Can I drink water or other beverages during a 48 or 72-hour fast?

Yes, staying hydrated is crucial during any fasting period. Water, herbal tea, and black coffee without added sweeteners or cream are generally acceptable to consume during fasting. However, it’s best to avoid calorie-containing beverages, as they can disrupt the fasting state.

  • Will I feel hungry during a 48 or 72-hour fast?

It is normal to experience hunger pangs, especially in the initial stages of fasting. However, many people find that hunger subsides as the body adjusts to the fasting period. Staying busy, staying hydrated, and consuming electrolytes can help manage hunger.

  • Can I exercise while on a 48 or 72-hour fast?

Light to moderate exercise is generally fine during a fast, but listen to your body and adjust accordingly. Intense workouts or prolonged physical activity may be more challenging during extended fasting periods. It’s important to prioritize rest and recovery while fasting.

  • Are there any specific considerations for breaking a 48 or 72-hour fast?

When breaking a prolonged fast, it’s essential to reintroduce food gradually. Start with easily digestible, nutrient-dense foods and avoid overeating. Your body may have adjusted to the fast, so it’s important to listen to your hunger cues and eat mindfully.

  • Can I continue intermittent fasting after completing a 48 or 72-hour fast?

Yes, you can resume your regular intermittent fasting routine after completing a prolonged fast if it aligns with your goals and preferences. However, it’s essential to ensure you’re providing your body with proper nourishment during feeding windows.

  • Are there any potential risks or side effects associated with prolonged fasting?

Prolonged fasting may not be suitable for everyone, especially those with underlying health conditions, pregnant or breastfeeding individuals, or individuals with a history of disordered eating. Side effects may include fatigue, dizziness, low blood sugar, or electrolyte imbalances. Consulting a healthcare professional before attempting prolonged fasting is advised.

  • Can I repeat 48 or 72-hour fasts regularly?

Regularly repeating prolonged fasts should be approached with caution and under professional guidance. It is essential to listen to your body and monitor how it responds to extended fasting. It’s generally recommended to have periods of regular nourishment between prolonged fasts to ensure overall well-being.

  • Can I take supplements or medications during a 48 or 72-hour fast?

It is crucial to consult with a healthcare professional regarding the intake of supplements or medications during a fast. Some medications may need to be taken with food, while others may be taken on an empty stomach. Professional guidance is recommended to ensure safety and effectiveness.

  • Are there any alternatives to prolonged fasting for achieving similar benefits?

Prolonged fasting is just one approach to intermittent fasting. There are various other fasting protocols, such as alternate-day fasting or time-restricted feeding, that can offer benefits similar to prolonged fasting. It’s important to find a fasting routine that suits your lifestyle and health needs.

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!