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Intermittent Fasting 20/4: What You Should Know Before Starting

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a plate with a salad with a clock on the background_intermittent fasting 20:4
Melissa Mitri post Reviewer Melissa Mitri post Reviewer
Verified by Melissa Mitri
MS, Registered Dietitian, Former President of CT Academy of Nutrition & Dietetics

Table of Contents

Intermittent fasting (IF) is practiced in various ways depending on the duration of the fasting and feasting windows. While the most popular schedule is 16:8, some try to follow more restrictive methods such as all-day-fasts, one meal a day (OMAD), and 18:6 fasting

Intermittent fasting 20/4 is another method that is more strict when compared to 16/8. Here we discuss the 20/4 intermittent fasting schedule in detail. We will be reviewing the health benefits and drawbacks of this eating pattern as well as its weight loss efficacy. 

What Is 20/4 Intermittent Fasting?

As you can guess by the name, 20/4 fasting is a type of intermittent fasting in which you will be fasting for 20 hours per day and eating in the remaining 4 hours. 

Before proceeding, we would like to mention that this method is one of the more restrictive intermittent fasting schedules, so we do not recommend it for beginners. 

If you’re just starting out with intermittent fasting, the best way is to start with more flexible routines such as 12/10 or 16/8 and ease into extended fasting periods. And if you’re a complete newbie to fasting, you can start by reading our beginner’s guide to intermittent fasting.

The 20/4 fast works similarly to other intermittent fasting routines. After around 6-8 hours of fasting, your body’s glucose reserves get depleted, and it starts to break down fat for energy production [1]. This state is known as the ketogenic state, and it’s the basis of many benefits of intermittent fasting. 

20/4 Intermittent Fasting vs. Warrior Diet

Intermittent fasting 20/4 is a variation rooted in the “Warrior Diet”—a diet invented by the health and fitness author Ori Hofmekler [2]

While these two diets share major similarities, they also have their differences. For instance, both these diets include a 20-hour fast followed by a 4-hour feast. 

However, in the Warrior diet, you can eat small portions of dairy, eggs, fruits, and vegetables during the fasting hours. In the 20/4 intermittent fasting method, you should stick to a complete fast within these 20 hours except for non-caloric beverages such as unsweetened tea, black coffee, and water. 

What Can You Eat During 20/4 Intermittent Fasting?

As we already said, you’re expected to completely avoid foods during your 20-hour fasting period, but you can have calorie-free drinks. During the eating window, you can technically eat whatever you want without any restrictions. 

However, it’s still wise to pay attention to your food choices—especially if you’re following intermittent fasting in the hopes of losing weight. Given that you only have 4 hours for eating, and food stays in your stomach for 1.5 to 2 hours [3], you will likely eat one meal—or two max. 

You will also have to pay attention to your portion sizes to keep yourself comfortable and not feel too full. 

Keep in mind that the quality of your diet matters as much as the quantity. Since you will eat a limited number of meals, you need to make sure that you get adequate nutrition through them. You will also need to choose foods that are more satiating over those that fill you up temporarily but make you hungry immediately after eating. 

With that said, it’s a good idea to include a healthy serving of proteins, complex carbs, healthy fats as well as fiber from fruits and vegetables in your meals. If you need further guidance, refer to our article on what you can eat or drink during IF.

How Long Can You Follow 20/4 Intermittent Fasting?

It’s difficult to set an exact timeline for 20/4 intermittent fasting. In the current scientific literature, there is not yet a definitive answer. 

However, there are some scientific studies where people followed 20/4 IF for as long as 8 weeks, so we can assume that it’s safe to practice a 20-hour fast for prolonged periods as long as you get enough nutrition during your feeding hours [4]

As for how long you personally can follow 20/4 intermittent fasting, we’d say it depends on your personal preference and grit. Since it’s a comparatively strict fast, you might not be able to stick to it over a very long period. Everyone is different here, and it’s important to choose the fasting method that works best for you.

Either way, you can practice it until you hit your weight loss or health goal and then ease back into a less-restrictive intermittent fasting method such as 16/8 as a maintenance strategy.

Pros And Cons Of 20/4 Intermittent Fasting

Research studies are scarce when it comes to 20/4 fasting, but we can safely say that the same health benefits of intermittent fasting apply to this specific routine. It also has its drawbacks and risks, and you need to carefully consider both the pros and cons before starting a 20/4 fast. 

Here are a few benefits and risks of a 20-hour fast:

Health Benefits of 20-Hour Fast

  • It can improve heart health
  • It can reduce inflammation
  • Reduces oxidative stress
  • Regulates the lipid profile
  • It can increase insulin sensitivity
  • It can improve the symptoms of metabolic syndrome
  • It can manage blood sugar and diabetes [5] [6] [7] [8] [9]

Drawbacks And Risks

  • It can be too restrictive for some people
  • You might feel increased hunger during fasting hours
  • It might trigger eating disorders in those who are prone to them
  • You can experience mood changes and increased irritability
  • You might feel fatigued more often [10] [11]

Can You Lose Weight On 20/4 Intermittent Fasting?

It has been proven through research studies that intermittent fasting can induce weight loss. One review reported that IF can bring about a loss of 7-10 pounds within 10 weeks. IF is thought to do this by restricting calorie intake, reducing appetite, and burning fat [12]

20-hour fasts, in particular, have also been found to help lose weight. It has been shown that limiting eating to a 4-hour window reduced energy intake by around 550 Kcal [4].  

However, keep in mind that it all depends on what and how much you eat during your eating window. If you binge on loads of high-calorie foods during the 4 hours you eat, you can still overdo it on calories and hinder weight loss.

If you need to count how many calories you’re eating during your 20/4 intermittent fasting period, you can use an all-in-one weight loss app to guide you. 

4 Tips for 20/4 Intermittent Fasting

Here are 4 tips that will increase your chances of success with a 20/4 fasting plan:

#1 Start Slow

As we said, it’s not a good idea to jump head first into a restrictive fasting method if you’re only a beginner. 

Start with more accommodating fasting periods, such as 8-10 hour fasts, and then gradually increase the fasting duration. In this way your body will have time to adapt to longer fasts and you’re more likely to achieve success.

#2 Choose Foods That Keep You Full Throughout The Long Fast

Since you have to fast for 20 hours, you will obviously feel hungry. Choosing foods with plenty of protein, fiber, and healthy fat will keep you satiated for longer, thus making you less hungry. 

#3 Follow a Meal Plan

You only have a limited number of meals per day, so you’ll want to make the most of it. Make sure you include nutrient-dense food that provides you with adequate macro-and micronutrients that your body needs, and limit ultra-processed foods like pastries, cookies, chips, and sugary beverages. 

Planning your meals ahead of time can help you include more nutritious food items in your diet without having to settle with whatever you have in your fridge.

#4 Consider Taking Vitamin And Mineral Supplements

Talk to your doctor about taking nutritional supplements to reduce the risk of nutritional deficiencies. 

Is 20/4 Intermittent Fasting Worth Trying?

Considering the benefits vs. risks of a 20-hour fast, we can conclude that a 20/4 intermittent fasting schedule is worth a try if you’ve already practiced less restrictive fasting methods. 

However, research has shown that both a 6-hour and a 4-hour eating window give the same weight loss results within 8 weeks [4]. Thus, from a weight loss perspective, it seems that there’re no additional benefits to following a more rigid fasting routine like 20/4. 

Whether try 20/4 fasting or not entirely depends on your personal preference and your health status. If you feel you need a strict schedule to keep you on track and control your food intake—go for it. 

However, such a plan will not be suitable for you if you’re under 18, pregnant, or underweight. You might also want to think twice if you have a history of eating disorders, as this level of restriction can bring up triggering thoughts and behaviors.

Wrapping Up

  • 20/4 fasting is a stricter way of intermittent fasting.
  • It can help you lose weight as well as ward off certain health conditions such as high blood pressure, high blood cholesterol, and diabetes.
  • It has its pros and cons and you need to carefully consider both before starting this routine.
Disclaimer This article is intended for general informational purposes only and does not address individual circumstances. It is not a substitute for professional advice or help and should not be relied on to make decisions of any kind. Any action you take upon the information presented in this article is strictly at your own risk and responsibility!

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