Fasting, the reduction of or abstinence from consuming food, is a practice that has been used since ancient times for various religious and health purposes.

Though fasting has a rich history, it has now become popular as a weight loss tool.

The Warrior Diet is a way of eating that cycles extended periods of little food intake with short windows of overeating. It has been promoted as an effective way to lose weight and improve energy levels and mental clarity.

Yet, some health experts argue that this fasting method is extreme and unnecessary.

This article discusses everything you need to know about the Warrior Diet to help you determine if it’s a safe and effective way to improve your health.

Warrior Diet Guide

The Warrior Diet was created in 2001 by Ori Hofmekler, a former member of the Israeli Special Forces, who transitioned into the field of fitness and nutrition.

This diet is considered a type of intermittent fasting, an umbrella term for eating patterns that include periods of reduced calorie intake over a defined period.

The Warrior Diet is based on the eating patterns of ancient warriors, who consumed little during the day and then feasted at night.

According to its founder, it’s designed to “improve the way we eat, feel, perform and look” by stressing the body through reduced food intake, thus triggering “survival instincts.”

It should be noted that Ori Hofmekler himself acknowledges that the Warrior Diet is based on his own beliefs and observations — not strictly on science.

People following this diet undereat for 20 hours per day, then consume as much food as desired at night.

During the 20-hour fasting period, dieters are encouraged to consume small amounts of dairy products, hard-boiled eggs and raw fruits and vegetables, as well as plenty of non-calorie fluids.

After 20 hours, people can essentially binge on any foods they want within a four-hour overeating window.

However, unprocessed, healthy and organic food choices are encouraged.

To get started, dieters are urged to follow an initial three-week plan divided into phases that will be covered in detail later in this article.

Followers of the Warrior Diet claim that this method of eating melts fat, improves concentration, boosts energy levels and stimulates cellular repair.

Summary The Warrior Diet is a type of intermittent fasting that revolves around 20-hour periods of undereating, followed by four-hour periods of overeating.

The Warrior Diet does not have any research to back up its exact methods, but intermittent fasting does.

Though the Warrior Diet is a bit more extreme than other, more common types of intermittent fasting like the 16:8 method (fasting for 16 hours and then eating over the remaining 8 hours), it’s simply a stricter version of this method.

For this reason, one could argue that the benefits linked to intermittent fasting also apply to the Warrior Diet.

It May Aid Weight Loss

Various methods of intermittent fasting, including 20-hour fasting cycles, have been linked to weight loss.

One study, which closely mimicked the Warrior Diet (fasting for 20 hours), found that people who consumed meals over four hours in the evening experienced more weight loss than those who consumed the same amount of calories in meals throughout the day.

What’s more, those who ate one meal per day showed significantly reduced fat mass and greater muscle mass (1).

A recent review of six studies concluded that various types of intermittent fasting, ranging from 3 to 12 months, were more effective at promoting weight loss than no dietary intervention.

However, the review found that there were no significant weight loss differences between dieters using intermittent fasting or continuous calorie restriction (normal dieting), meaning that calorie restriction without fasting was equally effective (2).

Additionally, although reducing calorie intake is the most common outcome of the Warrior Diet, some people following this eating pattern could technically consume too many calories during the four-hour overeating period and experience weight gain.

Fasting May Improve Brain Health

The Warrior Diet is promoted as a way to improve brain health.

There may be some truth to that based on scientific studies on intermittent fasting.

Intermittent fasting has been found to benefit the regulation of inflammatory pathways that affect your brain function.

For example, animal studies have shown that intermittent fasting reduced inflammatory markers like interleukin 6 (IL-6) and tumor necrosis factor alpha (TNF-α), which may negatively impact memory and learning (3).

Other animal studies found that intermittent fasting has a protective effect against Alzheimer’s disease (4, 5).

However, research in this area is ongoing and more human studies are needed to determine the benefits of intermittent fasting on brain health.

It May Decrease Inflammation

Inflammation caused by oxidative stress is thought to be the cause of many diseases, such as heart disease, diabetes and certain cancers (6).

Studies have demonstrated that intermittent fasting may be an effective way to reduce inflammation in your body.

One study in 34 healthy men found that the 16:8 intermittent fasting method decreased levels of TNF-α and interleukin 1 beta (IL-1β), substances that promote inflammation (7).

Another study in 50 people found that those fasting for the Muslim holiday of Ramadan had significantly lower levels of the inflammatory markers IL-6, C-reactive protein (CRP) and homocysteine, compared to non-fasting individuals (8).

Fasting May Improve Blood Sugar Control

Some studies have found that intermittent fasting can improve blood sugar control in those with type 2 diabetes.

A study in 10 people with type 2 diabetes found that a fasting goal of 18–20 hours a day lead to a considerable decrease in body weight and significantly improved fasting and post-meal blood sugar control (9).

However, another recent study showed that intermittent fasting increased the chances of hypoglycemia (low blood sugar), even when taking lower doses of blood-sugar-reducing medications (10).

Though lowering blood sugar levels in a safe way is beneficial, hypoglycemia can be dangerous and lead to serious complications (11).

For this reason, people with diabetes who are interested in trying out intermittent fasting should consult with their doctor first.

Summary Methods of intermittent fasting like the Warrior Diet may help reduce weight, improve brain health, lower blood sugar and reduce inflammation.

Despite potential health benefits of the Warrior Diet, there are some downfalls to this way of eating.

It May Be Difficult for Some People to Stick To

One of the most obvious limitations of the Warrior Diet is that it restricts the time during which you may eat substantial meals to a four-hour period.

This can be difficult to stick to, especially when participating in normal social activities like going out to breakfast or lunch.

While some people may feel great when consuming very small amounts of calories over a 20-hour period, others may find that this way of eating is not ideal for their lifestyle.

It’s Inappropriate for Many People

The Warrior Diet is not a way of eating that everyone should follow.

This type of intermittent fasting is inappropriate for many people, including:

  • Children
  • Women who are pregnant or nursing
  • People with diseases like type 1 diabetes, heart failure or certain cancers
  • Extreme athletes
  • People with eating disorders or a history of disordered eating
  • People who are underweight

Moreover, some research suggests that intermittent fasting can affect women’s hormones more than men’s (12, 13).

Some women may be able to fast intermittently without negative effects. However, some may experience unpleasant side effects like insomnia, anxiety, missed periods and reproductive health disturbances.

It Could Lead to Disordered Eating

The Warrior Diet places an emphasis on overeating, which could be problematic for many people.

Though Ori Hofmekler argues that one should know to stop eating “when you feel pleasantly satisfied,” this may not translate into healthy eating practices for everyone.

The Warrior Diet could lead to binging and purging behaviors, especially in those at risk of developing disordered eating.

Binging on large quantities of food may also lead to feelings of regret and shame, which can negatively impact mental health and body image.

It Could Lead to Negative Side Effects

The Warrior Diet may lead to side effects, some of which could be severe.

Potential side effects include (14):

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

In addition, many health professionals argue that dieters will not get enough nutrients when following an intermittent fasting plan like the Warrior Diet.

However, as long as healthy, nutrient-dense foods are chosen and calorie needs are met, nutrient needs can be covered by carefully planning your food choices when following the Warrior Diet.

Summary The Warrior Diet is inappropriate for many people, can be hard to stick to and may lead to negative side effects such as fatigue, insomnia and hormonal imbalance.

Hofmekler suggests that anyone starting the Warrior Diet should follow an initial three-week, three-phase plan to “improve the body’s ability to utilize fat for energy.”

Phase I (week one): “Detox”

  • Undereat for 20 hours during the day on vegetable juices, clear broth, dairy (yogurt, cottage cheese), hard-boiled eggs and raw fruits and vegetables.
  • During the four-hour overeating period, eat a salad with oil and vinegar dressing, followed by one large or multiple meals of plant proteins (beans), wheat-free whole grains, small amounts of cheese and cooked vegetables.
  • Coffee, tea, water and small amounts of milk can be consumed throughout the day.

Phase II (week two): “High Fat”

  • Undereat for 20 hours during the day on vegetable juices, clear broth, dairy (yogurt, cottage cheese), hard-boiled eggs and raw fruits and vegetables.
  • During the four-hour overeating period in the evening, eat a salad with oil and vinegar dressing, followed by lean animal protein, cooked vegetables and at least one handful of nuts.
  • No grains or starches are consumed during phase II.

Phase III (week three): “Concluding Fat Loss”

This phase cycles between periods of high carb and high protein intake.

  • 1–2 days high in carbs
  • 1–2 days high in protein and low in carbs
  • 1–2 days high in carbs
  • 1–2 days high in protein and low in carbs

On high-carb days:

  • Undereat for 20 hours during the day on vegetable juices, clear broth, dairy (yogurt, cottage cheese), hard-boiled eggs and raw fruits and vegetables.
  • During the four-hour overeating period, eat a salad with oil and vinegar dressing, followed by cooked vegetables, small amounts of animal protein and one main carbohydrate such as corn, potatoes, pasta, barley or oats.

On high-protein, low-carb days:

  • Undereat for 20 hours during the day on vegetable juices, clear broth, dairy (yogurt, cottage cheese), hard-boiled eggs and raw fruits and vegetables.
  • During the four-hour overeating period in the evening, eat a salad with oil and vinegar dressing, followed by 8–16 ounces (227–454 grams) of animal protein with a side of cooked, non-starchy vegetables.
  • Though grains or starches are not to be consumed during the phase-III overeating window, a small amount of fresh tropical fruit can be eaten for dessert.

Hofmekler recommends that once dieters have completed the three phases, they should start them over from the beginning.

However, instead of going through the entire cycle again, you may also forgo the initial phases and simply follow the guidelines of undereating for 20 hours on low-calorie foods, followed by eating healthy, protein-rich meals to satisfaction during the overeating phase.

Note that serving sizes on the Warrior Diet are vague and there is no set calorie restriction.

Hofmekler recommends taking a daily multivitamin along with other supplements like probiotics and amino acids as part of this diet plan.

Dieters are also encouraged to incorporate exercise, including strength and speed training, into their routines to promote fat loss and to hydrate with plenty of water throughout the day.

Summary When beginning the Warrior Diet, dieters are encouraged to follow three distinct phases separated into weeks that include fasting during the day and overeating at night.

Although dieters are allowed to consume any food they like, whole, nutritious, organic foods are encouraged, whereas processed foods, preservatives, added sugars and artificial sweeteners should be avoided.

Foods to eat in small portions during the undereating phase:

  • Fruits: Apples, bananas, kiwi, mango, peach, pineapple, etc.
  • Vegetable juices: Beet, carrot, celery, etc.
  • Broth: Chicken, beef, etc.
  • Raw vegetables: Greens, carrots, peppers, mushrooms, onions, etc.
  • Condiments: Small amounts of olive oil, apple cider vinegar, etc.
  • Dairy: Milk, yogurt, cottage cheese, etc.
  • Protein: Hard-boiled or poached eggs
  • Beverages: Water, seltzer, coffee, tea, etc.

Foods to eat during the overeating phase:

  • Cooked vegetables: Cauliflower, Brussels sprouts, zucchini, greens, etc.
  • Proteins: Chicken, steak, fish, turkey, eggs, etc.
  • Starches: Beans, potatoes, corn, sweet potatoes, etc.
  • Grains: Oats, quinoa, pasta, bread, barley, etc.
  • Dairy: Milk, cheese, yogurt, etc.
  • Fats: Nuts, olive oil, etc.

Foods to avoid:

  • Candy
  • Cookies and cakes
  • Chips
  • Fast food
  • Fried foods
  • Processed meats (lunch meats, bacon)
  • Refined carbohydrates
  • Artificial sweeteners
  • Sweetened drinks like fruit juice and soda
Summary When following the Warrior Diet, nutritious foods like vegetables, fruits and lean proteins are encouraged. Processed foods and added sweeteners should be avoided.

The Warrior Diet is a type of intermittent fasting program that cycles 20-hour periods of little food intake with four-hour periods of overeating.

Though there is little research supporting the benefits of this particular type of fasting, intermittent fasting in general has been linked to a number of health benefits from weight loss to improved brain health.

While some people may thrive on the Warrior Diet, others may find its rules too difficult to follow.

In addition, this way of eating isn't appropriate for many people, including pregnant women and children.

Although the Warrior Diet may benefit certain individuals, the tried and true method of eating healthy, increasing activity and limiting overall calories is something everyone can follow.