20:4 Intermittent Fasting Guide: The Benefits + Tips for Success

Rich LaFountain, PhD

If you’re interested in intermittent fasting and considering which schedule might be best , this article is for you. Here is everything you need to know about the 20:4 intermittent fasting method to help you decide what fits your needs and lifestyle best. Keep in mind intermittent fasting (IF) should be flexible. If you try one option and want to switch things around then you can easily do so. Considering 20:4 IF is more challenging, many people work their way up to it. 

What Is 20:4 Intermittent Fasting?

20:4 IF is a type of intermittent fasting in which you fast for 20 hours and you eat during a 4 hour window. The 20:4 IF strategy is a variation of the popular 16:8 intermittent fasting, where the eating window is 8 hours. 20:4 IF requires more time restriction so it can be more challenging, and it enables some additional time for benefits like fat burning and autophagy to be realized.

Terminology note: Fasting less than 24 hours is often referred to as time-restricted feeding (TRF) or time-restricted eating (TRE). You may also have seen 20:4 TRF or 20:4 TRE elsewhere. Note that they are the same as the 20:4 IF.

Are OMAD and the Warrior Diet the Same as 20:4 Fasting?

While there are similarities between 20:4 intermittent fasting and other fasting protocols like OMAD (One Meal a Day) and the Warrior Diet, they are not exactly the same. OMAD involves fasting for roughly 23 hours and consuming all your daily calories within a very tight one-hour eating window. This approach is more extreme than 20:4 intermittent fasting, as it provides an even shorter eating window and a longer fasting period. OMAD can be challenging to sustain for some individuals due to its restrictive nature. In most cases OMAD is better suited to occasional use rather than a daily habit.

The Warrior Diet was invented by Ori Hofmekler and follows a 20-hour fast and a 4-hour eating window, similar to 20:4 IF. Although the fast duration is the same, the Warrior Diet couples the 20:4 IF with a specific eating pattern where you consume small amounts of raw fruits and vegetables throughout the day and have one large meal at night. This approach has its roots in the eating patterns of ancient warrior cultures, as the name suggests.

The Benefits of 20:4 Intermittent Fasting

Many of the benefits of 20:4 IF are extensions or enhanced benefits also associated with shorter duration fasting protocol. Here’s a look at the specific benefits that we find in the research associated with 20:4 IF.

Improved Insulin Sensitivity

20:4 IF has been shown to enhance insulin sensitivity, which is important for maintaining healthy blood sugar levels. The metabolic health and flexibility benefits apply to healthy individuals as well as people with insulin resistance or type 2 diabetes. Research suggests that condensing your eating window reduces total blood glucose spikes throughout the day and can improve your body’s ability to handle glucose and insulin.

Weight Loss

By restricting your eating window to four hours, 20:4 IF can create a calorie deficit, leading to weight loss, particularly fat loss. Research shows that 20:4 can produce a 3% reduction in body weight in 8 weeks. The studies reveal that energy intake was reduced by approximately 550 kcal/day as a result of following a 20:4 IF schedule, without calorie counting. Fasting for 20 hours helps your body tap into stored fat for energy, meanwhile the reduction in total eating window duration, and hormone shifts reduce hunger which helps naturally reduce overconsumption.

Reduced Inflammation

Intermittent fasting has been shown to decrease inflammation and oxidative stress in the body. Chronic inflammation is linked to various health conditions, including heart disease, diabetes, and certain cancers. Adopting a fasting practice including 20:4 IF can help you to reduce chronic low-grade inflammation that is known to influence disease risk and aging.

Better Brain Function

Potential cognitive benefits: Recent research suggests that intermittent fasting may have positive effects on brain health. It may improve cognitive function, protect against neurodegenerative diseases, and promote the growth of new nerve cells. Many researchers and clinicians now believe that common neurodegenerative diseases of the brain are linked or caused by poor metabolic function leading to energy crises in the brain and nervous system. Intermittent fasting improves overall metabolic health and energy flexibility which may prevent or correct problems in energy delivery to working brain cells. 

Increased Longevity

While research on the direct effects of 20:4 intermittent fasting on longevity is limited, some studies on intermittent fasting in general have shown promising results. One of the primary mechanisms by which IF promotes longevity is through the spontaneous reduction in calorie consumption. Calorie restriction enhances longevity in both animal and human trials. Intermittent fasting enables a natural reduction in calories as a secondary benefit to the overall metabolic health and hormone benefits independent of weight loss. 


Autophagy is the body’s natural process of cellular waste removal and recycling. Intermittent fasting is known to increase autophagy throughout the body’s cells so that older, damaged cellular machinery can be renewed and replaced. 20:4 IF is sufficient to turn on autophagy, which may help remove damaged cells, improve cellular function, and potentially reduce the risk of certain chronic diseases.

How to Do 20:4 Fasting

20:4 IF requires fasting for 20 consecutive hours throughout the night and a good portion of daylight hours. The best way to do this is with the support of an app like Zero. The foundational functionality of the Timer will help you keep track of your fast. Zero offers motivational features including health-focused content, videos, and more to help you get the most out of your fasting experience.

Tips for Success with 20:4 Intermittent Fasting

Start Gradually

If you’re new to fasting, it’s generally recommended to start gradually and allow your body to adapt. 

  1. Begin with a shorter fast. Try a fast lasting 12 or 13 hours. At Zero, we refer to 13 hour fasts as Circadian Rhythm Fasts, but you can also think of them as an overnight fast. For example, if you finish dinner by 7 PM, wait until 7 or 8 AM the next day before having breakfast. For most people this simply means they avoid having a late night snack and push their first meal or calorie-containing beverage back slightly. It’s healthy, easy, and  allows your body to adjust to fasting for a specific period each day.
  2. Gradually increase the fasting window. Once you feel comfortable with a 12-hour fasting window, gradually extend it. Add 30 minutes to an hour each week until you arrive at a 16-hour fast. This can be done by delaying your breakfast or advancing your dinner time.
  3. Transition to 20:4 fasting. Once you are successful with routine 16 to 18 hour fasts, the transition to a 20:4 fast will feel more doable. Many people find that increasing their routine fast duration by an hour or two can happen inadvertently if you get busy at work or you are not feeling hungry so you let your fasting time continue to roll for a little bit longer.

Choose the Right Eating Window

Selecting the correct 4-hour eating window largely depends on your lifestyle, preferences, and individual needs. Here are a few considerations to help you select the eating window for you:

  1. Schedule. Choose an eating window that aligns with your daily schedule. Consider work, social commitments, and family mealtimes. For example, if you have a traditional 9-5 job, you might prefer an eating window from 2 PM to 6 PM, allowing you a later first meal of the day and dinner with friends and/or family.
  2. Hunger. Pay attention to your body’s hunger cues and energy levels. Some individuals find it easier to skip breakfast and have their first meal later in the day. Others may prefer to break their fast early so they have an earlier dinner, or skip dinner all together. Experiment with different eating windows to find what feels most comfortable for you.
  3. Social factors. If you enjoy having dinner with family or friends, you may want to choose an eating window that allows you to participate in those events occurring later in the afternoon and evening hours. Flexibility is key.
  4. Listen to your body. If you find that you feel excessively hungry or are battling fatigue then, consider shifting your eating window to better accommodate your needs. The goal is to find a sustainable approach that supports your overall well-being. 

Stay Hydrated

It’s important to stay hydrated throughout the fasting period. Drink plenty of water, unsweetened tea, or black coffee to help curb hunger and maintain hydration levels. Black coffee and tea also can provide other benefits such as increased fat burning capacity and polyphenols that have additional health benefits. Electrolytes are a great addition to your non-caloric beverages as they can help you maintain your hydration levels more effectively.

Don’t Break Your Fast Too Soon

Breaking your fast too soon may cause you to lose out on some of the benefits associated with fasting for a full 20 hours. However, fasting with exact hour precision is not necessary. Many of the benefits highlighted above, even autophagy is gradually turned on according to a recent study after you reach 17 to 19 hours of fasting. If you break your fast earlier than planned, it might cause you to feel more hungry later, so be sure to eat enough whole and satiating foods during your eating window (especially if you plan on consecutive 20:4 IF days).

Consider Supplements 

When you’re targeting a 20:4 IF strategy some supplementation may be helpful. Protein, amino acid, and electrolyte supplementation are 3 of the most important options to consider in association with 20:4 IF.

Can I Exercise While 20:4 Intermittent Fasting?

Yes, you can exercise while following a 20:4 IF regimen. In fact, incorporating exercise into your lifestyle is likely to enhance the health benefits you get from fasting. Here are a few things to keep in mind:

  1. Workout timing. Depending on your preference and energy levels, you can choose to exercise during your fast or within your eating window. Some individuals prefer to exercise in a fasted state. However, others find it more comfortable to exercise after consuming a small meal or snack within the eating window. Experiment with different timings to see what works best for you.
  2. Intensity and duration. Exercising during your fast may provide added benefit in that it increases fat burning. This benefit is primarily limited to light or moderate intensity exercise. High intensity exercise won’t have the same fat-burning results and is probably best avoided during 20:4 IF. 
  3. Fuel and re-fuel adequately. After completing your workout, ensure that you refuel adequately during your eating window. There are compound effects if you exercise and do not replenish you are likely to find that your subsequent fast and workouts are more difficult. If this happens, reduce activity or increase your energy intake.

Can I Do 20:4 Intermittent Fasting Every Day?

While it’s possible to do 20:4 intermittent fasting (IF) every day, it’s important to consider your energy, lifestyle, and health needs first and foremost. 

  1. Personalization. While some individuals find it feasible and sustainable to practice 20:4 IF every day, others may prefer to alternate fasting days or incorporate periodic breaks. It’s essential to find a fasting schedule that works for you and supports your overall well-being.
  2. Flexibility. Intermittent fasting can be flexible. If you choose to follow 20:4 IF on a daily basis, you can still adjust the timing of your eating window to accommodate social events, special occasions, travel and a myriad of other factors that impact daily life. 
  3. Monitoring your body’s response. Pay attention to how your body responds to daily 20:4 fasting. It’s crucial to assess your energy levels, hunger cues, and overall well-being. If you consistently feel fatigued, excessively hungry, or experience negative effects on your mood or performance, you may need to modify your fasting routine or consider a different approach with a longer eating window. 
  4. Individual considerations. Some individuals, such as those with specific medical conditions, pregnant women or breastfeeding women, or individuals with a history of eating disorder, disordered eating, may need to approach intermittent fasting with caution or avoid it altogether. It’s important to consult with your healthcare providers or registered dietitian to ensure the fasting approach is appropriate for your individual circumstances.

Will I Lose Muscle Mass When 20:4 Fasting?

When done properly, 20:4 intermittent fasting (IF) is not associated with massive muscle loss. However in all weight loss scenarios there is a mixture of body fat and lean mass loss that occurs. Here are key considerations to help preserve muscle mass during 20:4 fasting:

  1. Sufficient protein intake. Adequate protein consumption is essential for preserving muscle mass. Make sure to include ample protein, such as poultry, fish, lean meats, legumes, and plant-based protein sources, in your meals during your eating window. Shooting for a total protein target of no less than 100 grams per day or 1 gram per pound of body weight are important dietary considerations.  
  2. Resistance training. Engaging in resistance training exercises, such as weightlifting or bodyweight exercises, can help stimulate muscle growth and maintenance. Including strength training in your exercise routine while practicing 20:4 fasting can signal to your body that your active muscle tissue needs to be maintained.
  3. Caloric intake. While practicing 20:4 IF, it’s important to ensure that you’re eating enough food to meet your nutritional needs, which are individual to everyone. Fuel up on whole, minimally processed, nutrient-dense foods, and pay attention to whether you’re feeling satiated throughout the day. Doing so gives your body enough energy to support muscle maintenance and function, and it also prevents it from looking for energy elsewhere and burning the protein found in your muscles.

What Are the Risks and Challenges of 20:4 Intermittent Fasting?

The largest risk in undergoing the 20:4 IF regimen is a failure to consume enough essential nutrients, vitamins, and minerals. If you want to have a 20:4 IF routine then you must focus on a balanced, high quality diet during your eating window. 

Some individuals may feel tempted to overeat or engage in binge eating poor quality or junk food during their eating window, especially if they have been fasting for a prolonged period. It’s crucial to approach the eating window with mindful eating practices and focus on highly nutritious meals and snacks rather than using it as an opportunity to consume empty calories, especially because of the smaller time frame that 20:4 IF allows for you to meet your nutrition needs.


20:4 IF is a powerful tool to build metabolic health and flexibility once you become experienced with fasting. Prepare to couple your 20 hour fasting practice with a well-rounded healthy approach to your nutrition during a condensed eating window.

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