20/4 Intermittent Fasting: The Pros and Cons of a Longer Fast

Written by Stephen Anton PhD on January 25th, 2023

There are so many different approaches to intermittent fasting that it can be difficult to determine which approach is right for you.

The truth is that there are pros and cons to each of the options but the more you understand these pros and cons the better you can select the type that suits your goals.

An advanced approach that is described in this blog is the 20/4 intermittent fasting plan. This is a particular type of intermittent fasting called time-restricted eating, which involves extending the fasting period to be approximately 20 hours on a daily basis.

Let’s learn more about the 20/4 plan and how it compares to other approaches to fasting.

Popular Approaches to Intermittent Fasting

When most people think about intermittent fasting, they typically think of daily fasting for a period of 14 – 16 hours. Indeed, the 16:8 approach to intermittent fasting is one of the most popular approaches out there.

The good news is that a recent study shows this type of fasting does not affect the rate of muscle protein synthesis in older adults.(1) This suggests the 16:8 plan does not have any adverse effects on muscle growth and therefore can be practiced by individuals who desire to gain muscle.

Potential Limitations of the 16/8 Fast

What is not currently clear is whether the 16:8 plan is the optimal approach or whether greater metabolic benefits, including autophagy and fat loss, could occur from extending the daily fasting period beyond 16 hours.

Another popular approach is the 18:6 plan. In theory, this approach should result in even greater fat loss than the 16:8 plan, as the longer daily fasts are more likely to activate the body’s metabolic or fat burning switch.(2,3)

The 20/4 Intermittent Fasting Plan

The 20:4 plan would take the daily approach to fasting to another level. It is an advanced method of fasting that has the potential to provide a number of metabolic benefits if done correctly.(4,5)

Potential Benefits of the 20/4 Fast

The 20/4 approach is highly likely to activate the body’s metabolic switch(6) and lead to increased levels of ketones from the mobilization of body fat.(7)

Potential Problems of the 20/4 Fast

On the other hand, there may also be an increased risk of muscle loss, if this type of fast is not done correctly.(8) For this reason, the 20:4 plan should only be practiced after less intense forms of intermittent fasting (e.g., the 16:8 and 18:6 plans) have been mastered.

The good news is that recent studies have shown this approach can work successfully for increasing ketone levels in the blood.(9) So preliminary evidence is promising, but much more work is needed to understand the effects of this approach.

How to Start the 20/4 Intermittent Fasting Plan

When you plan to extend your daily fasting periods, it can be helpful to have guidelines to determine whether or not you should continue fasting or should break the fast. Below is a list of key signs that I believe indicate you are in a healthy fasted state and can continue with the fast.

Signs of a Healthy Fasted State:

None or only minor feelings of hunger

Great focus and mental clarity

Energized yet calm feeling

Happy and enthusiastic feelings about life

Relaxed muscles

Absence of headache, dizziness, and light-headed feelings

Capable of working at a high-level

This is not an exhaustive list, but I think it is enough to help you evaluate if you are in a healthy fasting state or not. If you are experiencing one or more of the above signs while fasting, you have most likely activated your metabolic switch and can feel comfortable continuing with the fast.

How to Know When to Stop a 20/4 Fast

On the other hand, there are some key symptoms that would suggest you are not in a healthy fasted state and should consider breaking the fast.

Symptoms of an Unhealthy Fast:

Extreme hunger

Headache

Low energy or fatigue

Dizziness

Trouble focusing

These symptoms often arise when we attempt to fast for longer than our body has become accustomed to fasting. If you experience any of these symptoms, then it is likely wise to break the fast and slowly try to extend it in the future.

20/4 Intermittent Fasting Diet Tips

An important consideration is what to eat during the four-hour eating window.

Eat Two Meals During the Eating Period

First and foremost, I would highly recommend consuming two meals during the eating window, one at the beginning and one at the end.

The reason for this is because it is virtually impossible to consume all of your body’s energy and protein needs in a single meal. By consuming two meals, you can distribute the protein and other macronutrients evenly between the meals.

Unless you are specifically trying to lose weight, your meals can and should be relatively large and comprised of all three macronutrients (fats, protein, and carbohydrates) in order to meet your body’s energy needs.

If your goal is to lose fat, however, then I would recommend to reduce consumption of calories from carbohydrates and fats at each meal but still maintain a high protein intake as protein is needed to support your body’s lean tissue (muscle mass).

Avoid Eating Only One Meal

Even if you have the ability to consume a large number of calories in a single sitting, I would not recommend to do this, as you can easily overload your metabolic system and send the signal to store body fat. This would be counter to the goals of the 20:4 plan and thus has the potential to negate the benefits of the extended fasting period.

For these reasons, I am not a fan of the one meal per day (OMAD) approach to fasting for most people.(10)

How to Time the 20/4 Fast

In terms of time of day to consume the meals, most people find that the early afternoon works best for them. In general, you want to align the fasting and eating periods with your body’s natural circadian rhythms. This means not eating during the night time, when the cellular process of autophagy is most active, and focusing on consuming all calories during the day time.

For these reasons, I would recommend to have the four-hour eating period fall sometime between the hours of 12 – 8 pm as this is the time when your body is most prepared to digest large amount of calories. However, there is no perfect time and it may require a bit of experimentation to determine the eating window that works best for you.

20/4 Intermittent Fasting Overview

Longer fasts have the potential to provide greater benefits in regards to autophagy, fat loss, and overall health.

In order to receive more benefits, your body will need to learn how to adapt to an increased fasting period.

In this case, the key to practicing 20/4 intermittent fasting correctly is to work your way towards this goal.

If you have been practicing intermittent fasting already, I recommend to try to extend your fasting period by 30-60 minutes per week and evaluate how you feel until you achieve a comfortable 20/4 fast.

If you are new to fasting, then I suggest to start with a 12-14-hour fast until you are comfortable with this fasting time, and then continue adding 30-60 minutes to your fasting period per week.

ABOUT THE AUTHOR

Dr. Anton

I’ve had the privilege of studying the fields of obesity, metabolism, and aging for the past 20 years and felt an increasing desire to share what I’ve learned with as many people as possible the past few years.

RECENT ARTICLES

20/4 Intermittent Fasting: The Pros and Cons of a Longer Fast

Written by Stephen Anton PhD on January 25th, 2023

There are so many different approaches to intermittent fasting that it can be difficult to determine which approach is right for you.

The truth is that there are pros and cons to each of the options but the more you understand these pros and cons the better you can select the type that suits your goals.

An advanced approach that is described in this blog is the 20:4 intermittent fasting plan.

This is a particular type of intermittent fasting called time-restricted eating, which involves extending the fasting period to be approximately 20 hours on a daily basis.

Let’s learn more about the 20/4 plan and how it compares to other approaches to fasting.

Popular Approaches to Intermittent Fasting?

When most people think about intermittent fasting, they typically think of daily fasting for a period of 14 – 16 hours.

Indeed, the 16:8 approach to intermittent fasting is one of the most popular approaches out there.

The good news is that a recent study shows this type of fasting does not affect the rate of muscle protein synthesis in older adults.(1)

This suggests the 16:8 plan does not have any adverse effects on muscle growth and therefore can be practiced by individuals who desire to gain muscle.

Potential Limitations of the 16/8 Fast

What is not currently clear is whether the 16:8 plan is the optimal approach or whether greater metabolic benefits, including autophagy and fat loss, could occur from extending the daily fasting period beyond 16 hours.

Another popular approach is the 18:6 plan.

In theory, this approach should result in even greater fat loss than the 16:8 plan, as the longer daily fasts are more likely to activate the body’s metabolic or fat burning switch.(2,3)

The 20/4 Intermittent Fasting Plan

The 20:4 plan would take the daily approach to fasting to another level.

It is an advanced method of fasting that has the potential to provide a number of metabolic benefits if done correctly.(4,5)

Potential Benefits of the 20/4 Fast

The 20/4 approach is highly likely to activate the body’s metabolic switch(6) and lead to increased levels of ketones from the mobilization of body fat.(7)

Potential Problems of the 20/4 Fast

On the other hand, there may also be an increased risk of muscle loss, if this type of fast is not done correctly.(8)

For this reason, the 20:4 plan should only be practiced after less intense forms of intermittent fasting (e.g., the 16:8 and 18:6 plans) have been mastered.

The good news is that recent studies have shown this approach can work successfully for increasing ketone levels in the blood.(9)

So preliminary evidence is promising, but much more work is needed to understand the effects of this approach.

How to Start the 20/4 Intermittent Fasting Plan

When you plan to extend your daily fasting periods, it can be helpful to have guidelines to determine whether or not you should continue fasting or should break the fast.

Below is a list of key signs that I believe indicate you are in a healthy fasted state and can continue with the fast.

Signs of a Healthy Fasted State:

None or only minor feelings of hunger

Great focus and mental clarity

Energized yet calm feeling

Happy and enthusiastic feelings about life

Relaxed muscles

Absence of headache, dizziness, and light-headed feelings

Capable of working at a high-level

This is not an exhaustive list, but I think it is enough to help you evaluate if you are in a healthy fasting state or not.

If you are experiencing one or more of the above signs while fasting, you have most likely activated your metabolic switch and can feel comfortable continuing with the fast.

How to Know When to Stop a 20/4 Fast

On the other hand, there are some key symptoms that would suggest you are not in a healthy fasted state and should consider breaking the fast.

Symptoms of an Unhealthy Fast:

Extreme hunger

Headache

Low energy or fatigue

Dizziness

Trouble focusing

These symptoms often arise when we attempt to fast for longer than our body has become accustomed to fasting.

If you experience any of these symptoms, then it is likely wise to break the fast and slowly try to extend it in the future.

20/4 Intermittent Fasting Diet Tips

An important consideration is what to eat during the four-hour eating window.

Eat Two Meals During the Eating Period

First and foremost, I would highly recommend consuming two meals during the eating window, one at the beginning and one at the end.

The reason for this is because it is virtually impossible to consume all of your body’s energy and protein needs in a single meal.

By consuming two meals, you can distribute the protein and other macronutrients evenly between the meals.

Unless you are specifically trying to lose weight, your meals can and should be relatively large and comprised of all three macronutrients (fats, protein, and carbohydrates) in order to meet your body’s energy needs.

If your goal is to lose fat, however, then I would recommend to reduce consumption of calories from carbohydrates and fats at each meal but still maintain a high protein intake as protein is needed to support your body’s lean tissue (muscle mass).

Avoid Eating Only One Meal

Even if you have the ability to consume a large number of calories in a single sitting, I would not recommend to do this, as you can easily overload your metabolic system and send the signal to store body fat.

This would be counter to the goals of the 20:4 plan and thus has the potential to negate the benefits of the extended fasting period.

For these reasons, I am not a fan of the one meal per day (OMAD) approach to fasting for most people.(10)

How to Time the 20/4 Fast

In terms of time of day to consume the meals, most people find that the early afternoon works best for them.

In general, you want to align the fasting and eating periods with your body’s natural circadian rhythms.

This means not eating during the night time, when the cellular process of autophagy is most active, and focusing on consuming all calories during the day time.

For these reasons, I would recommend to have the four-hour eating period fall sometime between the hours of 12 – 8 pm as this is the time when your body is most prepared to digest large amount of calories.

However, there is no perfect time and it may require a bit of experimentation to determine the eating window that works best for you.

20/4 Intermittent Fasting Overview

Longer fasts have the potential to provide greater benefits in regards to autophagy, fat loss, and overall health.

In order to receive more benefits, your body will need to learn how to adapt to an increased fasting period.

In this case, the key to practicing 20/4 intermittent fasting correctly is to work your way towards this goal.

If you have been practicing intermittent fasting already, I recommend to try to extend your fasting period by 30-60 minutes per week and evaluate how you feel until you achieve a comfortable 20/4 fast.

If you are new to fasting, then I suggest to start with a 12-14-hour fast until you are comfortable with this fasting time, and then continue adding 30-60 minutes to your fasting period per week.

ABOUT THE AUTHOR

Dr. Anton

I’ve had the privilege of studying the fields of obesity, metabolism, and aging for the past 20 years and felt an increasing desire to share what I’ve learned with as many people as possible the past few years.

RECENT ARTICLES

Get the Beginner’s Guide to Intermittent Fasting

Take advantage of this FREE PDF and learn the basics of intermittent fasting.

    ABOUT THE AUTHOR

    Dr. Anton

    I’ve had the privilege of studying the fields of obesity, metabolism, and aging for the past 20 years and felt an increasing desire to share what I’ve learned with as many people as possible the past few years.

    RECENT ARTICLES

    Get the Beginner’s Guide to Intermittent Fasting

    Take advantage of this 100% free PDF and learn the basics of intermittent fasting.

      Get the Beginner’s Guide to Intermittent Fasting

      Take advantage of this FREE PDF and learn the basics of intermittent fasting.