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.
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)
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.
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.
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.
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).
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.