Intermittent fasting is growing more and more popular with not just low carb diets, but all types of diets today – and with good reason.

The weight loss effects that can be attributed to intermittent fasting can be pretty impressive, which is why people have also started to branch out into other types of intermittent fasting as well.

There’s a variety of ways you can implement intermittent fasting into the ketogenic diet, and in this article I’ll be focusing on the 20/4 fasting protocol, otherwise known as the Warrior Diet.

What Is Intermittent Fasting?

Intermittent fasting is a term that can be used to describe a multitude of different eating schedules that are characterized by a cycle between periods of eating, and periods of fasting over a specific amount of time.

Intermittent fasting is particularly popular because it has been proven to yield impressively quick weight loss results, with fewer poor side effects than traditional calorie deficit diet plans.

How does intermittent fasting work?

Intermittent fasting effects the body in a variety of ways.

On a hormonal level, intermittent fasting has been linked to changes in hormones that are essential to metabolic function, fat production and storage, and hunger. When you fast for extended periods of time, these hormonal changes shift to help your body burn more body fat and reduce hunger during those anticipated new fasting windows.

Another way intermittent fasting contributes to weight loss is simply because you’re less likely to consume as many calories as you would on a normal eating schedule.

With a restricted window, most people tend to consume fewer calories during the day, and tend to eat during times of days when the body is most active so that they can burn calories easier than they would right before going to sleep.

Why do people fast intermittently?

The reasons behind intermittent fasting can vary pretty wildly.

In many cultures and religions, fasting is a custom that’s been followed for generations. It’s been observed all over the world throughout different eras of history, with different underlying reasons behind each.

Furthermore, doctors have been recommending fasting for certain types of conditions like epilepsy and diabetes to help manage symptoms more accurately for years.

Of course one of the biggest reasons the majority of modern people choose to fast intermittently is because of the weight loss benefits and restored or even increased levels of energy.

Intermittent fasting on keto

Many nutritionists and researchers have found that combining intermittent fasting with the keto diet is an extremely effective way to maximize both of their respective benefits.

It’s been observed that intermittent fasting can actually help a lot of people get into ketosis faster, especially if they’re new to the keto diet and are experiencing some trouble fully entering ketosis.

Furthermore, intermittent fasting in its own right can help contribute to fat loss by burning through fat stores within the body, similarly to that of keto, so when both are used simultaneously, the results can be pretty powerful in a fairly short period of time.

Types of intermittent fasting

There’s a few different types of intermittent fasting routines that you can choose from, and all have different respective pros and cons. Some of the most common ones include

• 16/8 – fasting for 16 hours with an 8 hour eating window
• OMAD (One Meal A Day) – Only eating one meal a day, and fasting the other 23 hours out of the day
• Eat-Stop-Eat – Doing a full 24 hour fast, at least once or twice per week
• 5:2 Diet – Fasting for two full days out of the week, and eating regularly the other five days
• Alternate-Day Fasting – Fasting every other day
• The Warrior Diet (20/4 Fast) – Fasting for 20 hours out of the day, with a 4 hour eating window

I’ll break down how all of these compare to each other later in this post. First, let’s dive deeper into the Warrior Diet.

What Is the Warrior Diet?

The Warrior Diet, often referred to as the 20/4 diet is a relatively new types of intermittent fasting that involves fasting for a 20 hour window, while restricting your eating time to a 4 hour window.

It’s name comes from the literal feasts that warriors would eat in short periods of time in the Roman empire days, and the feasting aspect is definitely encouraged.

Dieters following this fasting protocol are recommended to consume 80 to 90 percent of all of their calories during this tight window. The actual calorie amounts vary, and there aren’t many restrictions aside from a slight decrease in caloric intake compared to what you’d usually eat.

For example, someone who is active and needs 3,000 calories per day would be advised to consume 2,700 calories within their eating window.

Warrior Diet Background

The Warrior Diet is a specific type of intermittent fasting that was developed by a nutrition author named Ori Hofmekler. Hofmekler created this fasting protocol in 2001 after he had been observing himself and his colleagues in the Israeli Special Forces for years.

He found that the Warrior Diet resulted in a lot of the same benefits as standard intermittent fasting, but at a much more accelerated rate, and he attributed that to the protocol’s much larger, 20 hour fasting window.

While there isn’t a whole lot of research on the Warrior Diet compared to traditional 16/8 intermittent fasting, there are a lot of case studies available that you can read about in Ori Hofmekler’s own book titled The Warrior Diet: Switch on Your Biological Powerhouse for High Energy, Explosive Strength, and a Leaner, Harder Body.

How The Warrior Diet Works

The Warrior Diet is fairly simple. As mentioned above, it consists of fasting for about 20 hours, usually including sleep hours overnight, and overeating during a four hour window, typically around the evening.

It’s guiding principle comes from the idea that our ancestors spent their days hunting and gathering, and would all feast within a short period of time at night.

The 20/4 fast affects the body similarly to how other protocols of intermittent fasting do, but at a slightly accelerated rate due to increased fast burning from the longer fasting window.

The three phases of the Warrior Diet

When starting out, it’s often recommended that early adopters of the Warrior Diet stick to three distinct phases to assist with their transition period, to avoid side effects and potential hazards that come from overeating.

These phases are recommended to take place over the course of three weeks, with one week per phase.

• Phase 1

The first phase is referred to as the Detox Phase, which involves just under-eating during the 20 hour fasting window rather than fasting altogether. While under-eating, it’s recommended to focus on light foods like vegetable juices, bone broth, dairy, and hard boiled eggs.

During the four hour overeating period, it’s also recommended to eat mostly salads along with main dishes consisting of plant based proteins like peanut butter, almond butter, and beans. For keto dieters, plant-based burgers like the Beyond Burger can take the place of beans and grains.

• Phase 2

From there, phase two begins, which is referred to as the High Fat Phase.

This should be fairly easy for anyone already accustomed to the keto diet, as a primary goal is to be fully fat adapted with 60-70% of all calories coming from fat.

During this phase, you’ll want to follow the same style of under-eating during the 20 hour fasting window on a lot of the same types of foods, while introducing heartier meats into the four hour eating window along with fattier foods like coconut oil and avocado.

• Phase 3

The final phase is referred to as the Concluding Fat Loss Phase.

Traditionally, this phase consists of alternating between high carb days and high protein days. However for the keto diet, you’ll want to ignore this phase and continue aiming to hit your keto fat and protein macro goals.

It’s often easier for keto dieters to fully ease into The Warrior Diet after the first two phases if they’ve been in ketosis for a while, so sticking to phase three isn’t necessary.

Benefits of The Warrior Diet on Keto

• Can aid with weight loss

There’s a lot of evidence out there that connects all types of intermittent fasting to accelerated weight loss, especially that of a 20-hour cycle with the Warrior Diet.

One study in particular, which closely mirrored that of the Warrior Diet (fasting for 20 hours and eating in a window of 4 hours), discovered that people who consumed meals over that four hour timespan at the end of the day yielded more weight loss than those groups who consumed the same amount of calories but in meals eaten throughout the entire day.

Those who ate one meal per day also noticed significantly reduced fat mass compared to the other group.

• May improve brain health

The Warrior Diet is often recommended as an alternative option to improve overall brain health and cognitive function.

There’s been a large amount of scientific studies backing up all types of intermittent fasting on brain health, especially with longer fasting periods like alternate day fasting and the 20/4 Warrior Diet.

These brain benefits arise primarily because fasting has been linked to boosting the regulation of specific inflammatory pathways that affect how your brain operates.

As one example example, recent animal studies have discovered that intermittent fasting in test subjects resulted in reduced inflammatory markers such as interleukin 6 (IL-6) and tumor necrosis factor alpha (TNF-α), which have both been linked to negatively impacting memory and learning abilities.

• May decrease inflammation

Inflammation is generally caused by a type of stress known as oxidative stress, which is often considered to be the cause of a variety of other types of diseases like heart disease, diabetes, hypertension, and certain types of cancer.

Too much inflammation can also easily take your body out of ketosis, which is why eating low or anti-inflammatory foods is such an important component of the keto diet.

Studies have also found that intermittent fasting might be an effective way to reduce inflammation throughout the body, especially fasting variants like the Warrior Diet, where the eating window is particularly restricted.

• Can help regulate blood sugar

Another vital component of the keto diet is maintaining constant, low blood glucose levels so that ketones can propser in the blood stream.

Recent studies have shown that all types of intermittent fasting can improve blood sugar control, particularly within those with type 2 diabetes as well as those who are following low carb diets.

One specific study identified 10 people with type 2 diabetes and discovered that a fasting goal of 18–20 hours a day (similar to that of the Warrior Diet) resulted in a significant decrease in body weight and significantly improved fasting and post-meal blood sugar control.

• May reduce risk of Alzheimer’s

Recent animal studies have found that different types of intermittent fasting may be able to help protect against certain types of cognitive diseases like Alzheimer’s as well as general decline in cognitive function.

More research is definitely needed, but the results are in line with the other short-term cognitive effects observed in intermittent fasting.

Best Keto Foods for The Warrior Diet (300)

When it comes to what’s best to eat when following the Warrior Diet, a lot of what you’ll find around the internet today focuses on a balance of protein, fats, and carbs. Obviously that’s not in line with the ketogenic diet, and defeats the purpose of combining the two methods.

That’s why I’ve compiled some of the most important foods for the Warrior Diet that are also keto-friendly.

With the 20/4 fasting protocol, you’ll still want to shoot for between 20 and 30 net carbs per day to maintain ketosis. Some dieters choose to have bulletproof coffee in the morning and not count it toward the eating window, whereas others are more strict. It’s really up to you.

For the four hour eating window, it’s best to focus on healthy, filling fats, and a decent amount of protein. To best achieve this, I like going with ground beef or turkey, cheese and butter, and a side of fortified protein-rich shakes.

My favorite shake mix for getting a healthy amount of MCTs and proteins is Perfect Keto’s Exogenous Base.

Other types of keto-friendly Warrior Diet foods often include:

• Eggs
• Cheese
• Leafy greens
• Low carb vegetables (carrots, celery, broccoli, cauliflower)
• Bone broth
• Coffee or tea
• Water or sparkling water
• Fish (tuna, salmon, crab)
• Chicken
• Turkey

Side Effects of The Warrior Diet on Keto

• Can be difficult to stick to

One of the big challenges of any intermittent fasting routine is that it’s not always achievable with most lifestyles. A lot of us are accustomed to three meals a day and snacks in between, and it can be tough to adjust your schedule and eating behavior to fit a new mold.

The Warrior Diet is one of the more difficult forms of intermittent fasting to stick to, because the eating window is so restricted, and it can be easy to give into certain cravings. This is amplified even more by the restrictions of the keto diet, which is why it’s advised to start one for a while before starting the other.

• Can lead to under-eating

While eating fewer calories on average is an acclaimed benefit of intermittent fasting and especially the 20/4 fast, a pretty big natural drawback of that is that you run the risk of not getting enough calories at all.

Under-eating can be dangerous especially to those who are trying to lose weight, as it can lead to binge eating, as well as some serious vitamin and mineral deficiencies that can make the entire dieting process more harmful than healthy.

This is especially true when combined with the keto diet, because without carbs or enough calories, your body can go into starvation mode, which puts your state of ketosis at risk.

• Inappropriate for many types of people

Intermittent fasting, and the Warrior Diet in particular is not generally seen as a type of eating schedule that’s meant for all types of people.

In fact, a lot of people should avoid 20/4 fasting and intermittent fasting altogether to avoid medical complications and other issues. The main groups that should avoid these types of fasting include:

• • Women who are nursing or pregnant
  • Extreme athletes
  • Children under the age of 17
  • People who struggle with type 1 or type 2 diabetes
  • People who struggle with heart failure or other serious variants of metabolic syndrome
  • People who are already too underweight
  • People with eating disorders or histories of disordered eating

• It could lead to disordered eating

The Warrior Diet generally suggests overeating to a certain degree, within that restricted 4 hour window for eating.

While overeating is the best way to get the calories your body needs in the short window that it has, it isn’t the best strategy for all types of people, and it can actually lead to some pretty bad habits and even disordered eating down the line if you already struggle with portion control.

The Warrior Diet, and intermittent fasting in general have been linked to increased likeliness of binging and purging behaviors in a lot of people. If you think you may be more susceptible to disordered eating, you should consult with your doctor first before embarking on the 20/4 fast.

• Other medical side effects

Along with the other downsides listed above, the Warrior Diet can be linked to a variety of other unwanted medical conditions depending on the user’s nutrition history, lifestyle, and genetics.

Some of the most commonly experienced potential side effects of the Warrior Diet include:

• • Dizziness
  • Anxiety
  • Fatigue
  • Insomnia
  • Low Energy
  • Lightheadedness
  • Constipation
  • Low blood sugar (hypoglycemia)
  • Extreme hunger
  • Irritability
  • Hormonal imbalance
  • Weight Gain
  • Fainting

Warrior Diet vs Other Types of Fasts

OMAD

The rules of the OMAD, or One Meal a Day diet are fairly simple to follow.

Essentially, you’ll only be eating one meal a day, in around the same four hour block of time every day so that your body gets on a consistent schedule. It’s similar to the 20/4 fast, but your eating window is just centered around one bulk meal, so it should only last up to an hour.

During the other 23 hours of your fast, you are allowed to drink beverages, but they have to be zero calorie beverage options like coffee or water.

16/8

The 16/8 fast is the most traditional out of all fasts, and is the one most people think of when they hear the phrase ‘intermittent fasting’.

As you may have guessed, the 16/8 method involves fasting every day for roughly 16 hours a day, while restricting your eating window to just 8 hours. Within that eating window, you should be able to fit between two or three meals, depending on meal size and how many snacks you prefer throughout the day.

Most people take advantage of their sleeping hours to take away the bulk of the 16 hour fast, and tend to eat foods in the late morning and early evening.

Therefore, the fast is pretty simple and easy to stick to. As long as you’re having late breakfasts and early dinners, you’re essentially following the method perfectly.

Eat-Stop-Eat

Eat-Stop-Eat is a relatively new type of intermittent fasting that has been gaining popularity lately.

This method involves a full 24 hour fast, about one to two times per week.

While it sounds complicated, it’s actually pretty simple and is kind of like how OMAD works. For example, if you finish eating dinner at 6PM one day, your next meal can’t be until 6PM the next day.

Because of this, it’s advised to try to stick to a specific window of eating so that you don’t eat too early or too late, and risk under or overeating on a given day.

Eat-Stop-Eat is one of the most effective forms of intermittent fasting because of how it helps keep your metabolism as active as possible.

There’s actually a system that’s been developed to help guide people into this type of fast. You can check out the Eat-Stop-Eat guide here.

5:2

The 5:2 diet generally involves eating regularly for 5 days out of the week, while restricting your calories to 500-600 days on the other two says of the week. The restricted days don’t actually have to be consecutive, and some people prefer to fast during them entirely rather than eating low calorie.

The 5:2 diet unfortunately has the smallest amount of research available because of how particular it is as a method, but it’s often revered as a fair comparison to standard intermittent fasting.

Alternate day fasting

Alternate Day Fasting simply means fasting every other day. There’s a variety of ways that you can implement this, and like the 5:2 diet, some of those ways involve allowing up to 500 calories during the fasting days.

As a rather intense version of intermittent fasting, alternate day fasting is definitely not recommended for beginners, as it can be pretty challenging to get used to.

Looking at benefits, alternate day fasting is pretty comparable to that of the Warrior Diet, so I tend to prefer the Warrior Diet of the two because its easier for my lifestyle.

Final Thoughts

With so many different ways to fast, there isn’t one perfect protocol to go along with keto.

However the evidence is certainly there that suggests the Warrior Protocol is one of the most effective ways to both get into ketosis quickly, and to help maximize the weight loss and energy boosting effects of keto.