What is Intermittent Fasting?
Intermittent fasting is a way of eating that has been used for centuries to support general health and wellbeing as well as for specific therapeutic benefits.
To intermittent fast simply means to take a designated break from consuming food for a specific time. This way of eating has been found to be effective for weight management and body fat loss and shows promise for disease prevention, improved cognitive function, metabolic health and even longevity.
One of the advantages intermittent fasting has over many diets and calorie-restrictive models is that it isn’t based on excluding particular foods or specific nutrients. While some types of intermittent fasting methods do consider your calorie intake during the hours of fasting, including the 20:4, most are focused on your eating patterns.
What is the 20:4 Method?
Often referred to as the “Warrior Diet”, the 20:4 fast was created by health and fitness writer, Ori Hofmekler, in 2001. This is one of the more extreme intermittent fasting methods and is based on Hofmekler’s observations and experience keeping fit while in the Israeli Special Forces.
The 20:4 fast is designed to reflect the eating patterns of ancient warriors and timing is the key. It’s based on the idea that in primitive times, people spent their days actively hunting and gathering before an evening feast. Those who follow the Warrior Diet claim that by eating in the evening, the body utilises the nutrients in line with its natural circadian rhythm.
By following this diet, you would fast or eat very little for 20 hours per day, followed by a 4-hour overeating window in the evening.
During the eating window, fasters are encouraged to consume up to 90% of their daily caloric intake or until they are completely full. There aren’t any guidelines around the types of food you can consume during the 4-hour period, however, it is encouraged you consume nutrient-dense whole foods where possible.
How Does it Differ from the 16:8 Method?
This plan may sound very similar to the 16:8 intermittent fast with just a smaller feeding window, however, it is actually very different to execute. Here’s why:
- You are fasting the majority of the day whereas on the 16:8 most of your fasting time is done while you are sleeping which makes it much easier to stick to.
- You are able to eat a small portion of specific foods during your 20-hour fasting window on the Warrior Diet.
- The four-hour eating window makes it much more difficult to consume your daily calories and meet your nutrient needs in such a limited time. It’s much easier to achieve this in eight hours.
- The original Warrior Diet places a much greater emphasis on the types of food you should be eating throughout the day and during your four-hour overeating period. Although the modern 20:4 diet has relaxed to allow you to eat what you want in your 4-hour window.
- The original Warrior Diet also included an exercise plan to maximise the fitness and weight loss benefits while dieting.
How to Successfully do the 20:4 Intermittent Fast
The Warrior Diet plan involves fasting for 20 hours during the day followed by overeating in a 4-hour window at night.
For example, you may set your feeding window at 6:00 pm to 10:00 pm. During this time you can eat as much as you want with an emphasis on unprocessed, organic whole foods particularly those high in dietary fats and protein.
After 10:00 pm, you fast or eat very small portions of specific foods such as raw fruit and vegetables until 6:00 pm the next day. It’s important you’re eating as fewer calories as possible during this time.
The method is best suited for people who have tried intermittent fasting before or who already consume a low-carb/ketogenic diet.
Hofmekler recommends you follow a three-week, three-phase plan initially before starting the Warrior Diet. This helps the body adapt to the eating and fasting schedule and become accustomed to using body fat as energy. This three-week introduction includes:
- 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.
Once you have completed the three-phase diet, it is recommended you start it again before following the 20:4 guidelines.
Depending on your goals, you may only adopt the 20:4 fasting method three times per week rather than making it a daily habit.
A Sample Day of a 20:4 Fast
7:00 am – Wake and drink 500 mL of water with lemon
9:00 am – Eat 1 boiled egg white, a handful of berries or 1 cup of green tea
1:00 pm – Drink grapefruit juice, 1 cup of yoghurt or ½ cup of raw vegetables
8:00 pm – Eat dinner containing protein, healthy fats and complex carbs
9:00 pm – Drink 1 cup of warm milk with turmeric
10:00 pm – Eat desserts such as dark chocolate or fruit custard
Tips to Start your 20:4 Fast
As this is one of the more extreme methods of intermittent fasting, it is recommended you do your research before you start and even consult with a dietitian or a nutritionist to ensure it is right for you.
The best resource for the original Warrior Diet is Hofmekler’s own book “The Warrior Diet: Switch on Your Biological Powerhouse for High Energy, Explosive Strength and a Leaner, Harder Body.”
To help you start your first 20:4 fast and successfully stick to it for the desired period of time, follow these tips.
Before you start:
- Choose the time to implement your 4-hour evening eating period
- Define your health goals and take the required measurements to collect a baseline
- Choose a date to commence your fast when you can strictly adhere to it for at least 14 days
- If you are overwhelmed or concerned about fasting, speak to a health professional or engage a coach to help you navigate the process
During your fast:
- Keep hydrated by drinking water and herbal tea throughout your fast
- Eat a substantial protein-rich meal in the evening
- Consider a quality protein powder
- Only snacking on the recommended low-calorie options in the 20-hour window.
- Focus on wholefoods, avoiding processed foods
- Exercise in a fasted state
- Practice slow and mindful eating when consuming meals
- Keep busy
Health Benefits of 20:4 Warrior Diet
The Warrior Diet is a form of intermittent fasting. However, it’s important to note, the 20:4 isn’t backed by any research. The diet was created by Ori Hofmekler and is based on his own observations and experiences during his time in the Israeli Special Forces.
There is no evidence directly linking a 20:4 fast with any of the benefits of intermittent fasting. Although there is some preliminary evidence that fasting on a 20-hour cycle or 24-hour fast may result in body fat loss and reduced risk of cardiovascular disease.
In some rats and mice studies, alternate day fasting for 24-hours did result in up to 30% overall calorie reductions, however, the results were mixed and the health benefits insignificant. The research was also not conducted using the Warrior Diet which is a daily regime.
Pros of the 20:4 Fasting Method
- May aid weight loss
- May enhance fitness gains
Cons of the 20:4 Fasting Method
- Little evidence linking its benefits
- Difficult to sustain
- May lead to binge-eating behaviour
- May lead to potential side effects
Side Effects and Risks of the 20:4
Any dieting plan or fasting regime does have its side effects and risks, and there is no one plan that is suitable for everyone.
The 20:4 or Warrior Diet is one of the more extreme forms of intermittent fasting with the extended period of fasting and as such the side effects may be greater. Before you commence the fast, it’s important to do your research and consider consulting a health practitioner to ensure it’s safe for you.
Some side effects of the 20:4 diet due to the duration of calorie restriction include:
- Tiredness or weakness
- Brain fog
- Irritability or mood swings
- Stress or anxiety
- Nutritional deficiencies
- Hormone disruptions
20:4 is not for Everybody
Like any dietary protocol, intermittent fasting is not an eating plan that suits everyone. As the 20:4 requires extended calorie restriction, it is recommended you speak with a trusted health practitioner before starting the plan.
The diet is not recommended for:
- Pregnancy and breastfeeding women
- Individuals under 18 years old
- If you’re underweight or have a history of an eating disorder
If you have a pre-existing medical condition such as insulin resistance or type 2 diabetes or are taking medications, it is strongly recommended you consult your general practitioner before considering the Warrier.
The bottom line
The 20:4 Warrior Diet is a strict form of fasting with no scientific evidence to suggest it will lead to weight loss, increased fat burning or improved energy levels as Hofmekler implied.
The basic premise of the 20:4 fast is that you are fasting for an extended period of time and increasing your food intake for a short feasting period. This intermittent fasting protocol may be an effective way to achieve your goals when executed properly, but it may be a challenging one for beginners to start with and does come with the risk of significant side effects
If you are considering a fasting method, it is important to speak to your health practitioner before you commence. It may also be worth trying evidence-based intermittent fasting protocols such as the 5:2 or 16:8 first.
Explore in more detail
- A Beginner’s Guide To Intermittent Fasting
- A Guide To The 16:8 Fast
- A Guide To The 20:4 Fast
- A Guide To The 5:2 Fast
- Intermittent Fasting And Exercise
- Intermittent Fasting And Hormone Balance
- Intermittent Fasting And Keto
- Intermittent Fasting And Type 2 Diabetes
- Intermittent Fasting And Weight Loss
- Intermittent Fasting: Tips To Starting Your First Fast
- Side Effects Of Intermittent Fasting
- Tips For Intermittent Fasting Success
- Top FAQs Of Intermittent Fasting