In recent years, intermittent fasting has taken the world by storm.
Promising you drastic fat loss, muscle gain and a plethora of health benefits.
One such fasting protocol is known as the 20:4 method.
But what exactly is the 20:4 fast? And is it the right dieting approach for you?
The 20:4 fast is an extreme eating method in which you fast or eat very little for 20 hours of the day, followed by a period of 4 hours of overeating, which is typically completed in the evening. Fasters will need to consume up to 90% of their total daily caloric intake, or until they are full, during this short fasting window.
The 20:4 fast can be an effective weight loss approach for some people.
However, it’s very drastic and most people will not adjust to it very easily.
So, today, we’ll be reviewing this intermittent fasting regime in detail.
To help you decipher whether it’s the right caloric restriction method for you.
Here’s what we’ll be covering:
- What is intermittent fasting?
- What is 20:4 fasting?
- How does 20:4 fasting work?
- Does 20:4 intermittent fasting work?
- How much weight can you lost with 20:4 fasting?
- How many calories to eat during 20:4 fasting?
- What to eat on 20:4 fasting?
Let’s dive in!
PS: Before we go further, it’s important to consult with your doctor before you proceed with any new nutrition plan or eating regime. This article is for general advice only and should not be taken as a specific recommendation for anyone.
Open Table of Contents
| What Is Intermittent Fasting?
So if you’re reading this article, it’s pretty clear that you want to loose weight off your body.
Perhaps you started Googling different diets or saw a post on Instagram.
Which helped you to discover the various intermittent fasting protocols like:
- 16:8 fasting (fast for 16hrs, eat for 8)
- 5:2 diet (eat for 5 days, fast for 2)
- OMAD (one meal a day)
- And finally, 20:4 fasting
But before we discuss the specifics of the 20:4 fast, let’s actually define what intermittent fasting is.
So what exactly is intermittent fasting?
Intermittent fasting is a method of calorie restriction in which you fast (not eat) for periods of time during a day or week, followed by periods of overeating, in an attempt to achieve a caloric deficit. Intermittent fasting works by having you consume fewer calories each day or week compared to what your body is burning.
Although there certainly other well-researched benefits of intermittent fasting like:
- Improved insulin resistance
- Increased visceral fat loss
- Reduced oxidative stress and inflammation
- Improve heart health
- And more!
The main mechanism by which it has you losing weight is via a caloric deficit.
Thus, this article will be focusing on the 20:4 fast’s efficacy for helping you lose weight through this medium.
But first, let’s take a look into where the 20:4 fast came to be, to give you a little context.
| What Is 20:4 Fasting?
In the late 90’s, Ori Hofmekler – now a health and fitness writer – was working with the Israeli Special Forces.
He observed the ‘high energy levels’, ‘explosive strength’ and ‘lean, hard bodies’ he and his fellow soldiers achieved by following long periods of fasting paired with short periods of feasting.
As a result, Hofmekler experimented with the 20:4 fast, also known as his ‘Warrior Diet’, an eating routine designed to mimic the eating patterns of ancient warriors.
This was back when people who spent their daytime actively hunting and gathering food to eat before feasting on it in the evenings.
People who follow the 20:4 pattern of eating capitalise on their body’s natural circadian rhythm in order to claim and store the nutrients consumed in this huge dinner meal.
So what exactly is the 20:4 approach to fasting? And what does it involve?
The 20:4 fast is an extreme eating method in which you fast or eat very little for 20 hours of the day, followed by a period of 4 hours of overeating, which is typically completed in the evening. Fasters will need to consume upwards of 90% of their total daily caloric intake, or until they are full, during this short fasting window.
It’s important to note that even Hofmekler acknowledges that the warrior diet is based upon his own experience, rather than from any imperial, well-researched evidence.
As such, you should proceed with caution with this eating approach and always seek medical guidance from a professional before giving it a try.
| How Does 20:4 Fasting Work?
The main mechanism by which the 20:4 diet works is that of a caloric deficit.
If you are eating fewer calories on a daily basis than you’re burning, your body has no choice but to metabolise the stored fat on your body as fuel.
As a result, you will begin to lose weight.
The 20:4 premise is that it is near impossible to eat more than 90% of your daily calories in such a short period of time (at least at the start).
For the first few days or even weeks of starting the 20:4 diet, you will most likely struggle to be able to consume such a large volume of food, especially if it is fibrous and nutritious.
Throughout the entire day, the 20:4 fast has you severely strict or entirely avoid eating anything which has energy (calories) in it.
Although most intermittent fasting protocols have you completely avoiding any calories during the fasting window, they warrior diet is a little more relaxed in its approach.
With a small handful of berries or a hard boiled egg being acceptable during fasting periods.
A typical 20 hour fast might commence at 10:00pm at night and continue throughout the evening and next day, all the way through to 6:00pm at night.
From 6:00pm – 10:00pm, you will then eat upwards of 90% of your total daily caloric expenditure, or until you are full.
Fasters are encouraged to prioritise eating nutritious foods, rather than gorging on junk food.
This ensures that your body is receiving all it’s necessary nutrients and will ensure you don’t end eating too many calories due to fatty, sugary, calorie-dense food choices.
If you don’t know how to measure this, you might like to try calculating your feasting meal using an app like MyFitnessPal or Cronometer.
| How Does 20:4 Differ From 16:8?
Although you may be tempted to lump 20:4 fasting in with its neighbour -16:8 fasting – and call them one and the same.
Don’t make that conclusion too quickly.
Although they still both fall under the umbrella term of intermittent fasting, in practise, they affect your lifestyle very differently.
Here’s why the 20:4 is different:
- You are fasting for the majority of your waking hours, not just skipping breakfast like in 16:8.
- The 20:4 diet does allow you to eat some selected foods, whereas the 16:8 does not.
- With only four hours available for eating, it’s extremely difficult to get that volume of food down.
- The original Warrior diet comes with a recommended exercise plan to maximise overall health, whereas the 16:8 does not.
- Many 20:4 advocates say you can eat whatever you want during your 4 hour window (we don’t agree with this point of view) whereas the 16:8 still recommend eating somewhat nutritious foods.
| How To Start 20:4 Intermittent Fasting
Hofmekler does not recommend starting 20:4 fasting cold turkey.
Instead, he suggests that you follow a three-week, three phase onboarding phase leading up to the Warrior Diet.
And believe me, it’s worth following.
When I first switched to the 16:8 diet (which is not even as extreme), I was met with a constantly rumbling tummy to the point where I felt nauseous and even a little light-headed.
Here are the three phases:
- Phase 1 – “Detox”
4-hour evening eating period: consume salad with a dressing and a large or a couple of smaller meals of plant protein, whole grains, cheese and cooked vegetables.
20-hour fast: consume vegetable juices, bone broth, yoghurt, cottage cheese, hard-boiled eggs, raw fruit and raw vegetables. Black coffee, tea, water and small portions of milk can be consumed during the fasting period. - Phase 2 – “High Fat”
4-hour evening eating period: consume salad with a dressing and a large meal of lean animal protein, cooked vegetables and a handful of nuts. Grains and starches are eliminated in this dieting phase.
20-hour fast: consume vegetable juices, bone broth, yoghurt, cottage cheese, hard-boiled eggs, raw fruit and raw vegetables. - Phase 3 – “Concluding Fat Loss”
This phase alternates the intake of high carb and high protein every second day.
On the high carb days: Consume as above in phase 2 with the addition of one main carbohydrate such as potatoes, pasta or oats.
On the high protein days: Consume as above in phase 2 including 227-454 grams of animal protein and a side of cooked, non-starchy vegetables.
| Does 20:4 Intermittent Fasting Work?
I personally have tried various approaches to intermittent fasting, most commonly the 16:8 fast, in which I fasted for a window of 16 hours and would eat for 8 hours.
I found it to be an extremely effective way to lose weight as long as I paired it with a calorie tracking application like MyFitnessPal.
But does the 20:4 version of intermittent fasting work too?
The 20:4 intermittent fasting protocol absolutely works to help you lose weight if you actually stick to the 90% daily caloric intake rule. However, over time many fasters find that their body will begin to adjust to taking on a large volume of food in a short window of time. This may slow or halt your weight loss due to eating too many calories.
As a result, you should always use the 20:4 fast with caution to ensure you’re not eating too much. And keep in mind that it is a very extreme way to eat and most people will not enjoy the transition.
Your body is a survival machine. It can detect energy deficits very quickly and will do everything in its power to ensure its survival.
I personally found that over time as my body started to adjust to my intermittent fasting regime, I could fit on far more food than before.
And during my eating windows, I felt incredibly hungry and could literally fill myself with anything and everything I laid eyes on.
| How Much Weight Can You Lose With 20:4 Fasting?
The amount of weight you can lose with 20:4 fasting really comes back to how aggressive you are with the caloric deficit.
When using 20:4 fasting, you can expect to lose anywhere between 0.125 lbs and 2lbs per week. Your rate of weight loss depends on a variety of factors, including the level of caloric deficit, your level of activity, as well as your physical characteristics such as sex, weight, muscle mass, etc.
For example, if your maintenance calories are 2000 per day and you stick to a 90% intermittent fasting diet, you can expect to lose around 0.4lbs a week.
A good way to work out how much weight you can lose with intermittent fasting over 6 weeks is by using the following calculation:
Maintenance calories x Deficit percentage (use .10 for 10%, .15 for 15% etc) x 7 Days x 6 Weeks / 3500.
This will tell you how many pounds you’ll over 6 weeks.
| How Many Calories To Eat During 20:4 Fasting?
Many advocates of intermittent fasting love it because they believe they can eat whatever they heck they want in one sitting a day, whilst still expecting to lose weight.
But trust me, having worked with hundreds of different clients using a plethora of various approaches to nutrition.
I can guarantee you that your body is going to adjust, and within a few weeks or months…
The weight you lost will slowly creep back on again as your body adjusts.
And eventually your body will be able to eat more than your daily caloric intake in 4-hour window.
So, to ensure that doesn’t happen, here’s how many calories you should be eating during a 20:4 fast:
When completing a 20:4 fast, you should aim for a caloric deficit of between 10-20% (80-90% of your total daily maintenance calories) in order to see any substantial weight loss, as well as to ensure that you keep the weight off once your body adjusts.
Sorry to break it to you, there’s no magic diet when it comes to losing weight.
They all work via the same mechanism – a caloric deficit.
| 20:4 Fasting Pros
- May be an effective weight loss strategy for many people, especially those who are time-poor and find eating inconvenient
- May promote fitness gains, however, the evidence is unclear
| 20:4 Fasting Cons
- Little evidence to support its claims
- Extremely difficult to start and maintain
- May lead to binge-eating behaviour
Any caloric restriction regime can cause side effects such as:
- Hunger
- Tiredness or weakness
- Brain fog
- Insomnia
- Irritability or mood swings
- Stress or anxiety
- Nutritional deficiencies
- Hormone disruptions
| 20:4 Fasting – Is It For You?
20:4 intermittent fasting is an extreme approach to eating that can certainly aid in weight loss, however, it’s not for the faint hearted.
If you’re new to fasting, perhaps try the 16:8 approach first, and if you enjoy it and achieve consistent weight loss, then the 20:4 fast might also be worth looking into.
Remember though, that eating healthy, nutritious and fibrous foods can never lead you astray.
And if you want to start losing weight, you absolutely need to be consistently in a caloric deficit. Period.
