Intermittent fasting (IF) continues to be one of the most popular eating plans for people trying to lose weight. It involves periods of abstaining from food, and is often combined with other diets, like the keto or low carb diet. (Here are 26 impressive before-and-after photos that show some serious transformations.) There are so many iterations: the 5:2 method, alternate-day fasting, the 14:10 diet, the eat-to-stop diet, and more. One that has garnered a lot of attention is the Warrior Diet.

ICYMI, the Warrior Diet was originally created in the early 2000s by Ori Hofmekler and based on his own experiences with it, which are outlined in his book by the same name. The diet initially revolved around very small "underfeeding" meals of dairy, eggs, fruits, and vegetables for 20 hours of the day and a four-hour "overfeeding" window.

"Essentially, it was a very early version of intermittent fasting and said to mimic ancient warriors' lifestyle of training and battling throughout the day and consuming a majority of their calories during the evening in one massive feast," explains Joel Totoro, RD, a sports dietitian and the director of sports science at Thorne Research in Scottsdale, Arizona. "Hofmekler's original plan also had exercise suggestions built into it."

It sounds pretty intense. Is it healthy, safe, and effective for weight loss? Here's what nutrition experts really think about the Warrior Diet.

How does the Warrior Diet work, exactly?

The diet has evolved from its original format since it was first created and the name was coined. More recently, the Warrior Diet has been interpreted as a strict 20-hour food fast and a four-hour fueling window, with various exercise requirements, says Totoro. This is also sometimes referred to simply as a 20:4 diet or 20:4 fasting.

The current Warrior Diet involves fasting for 20 hours and eating during a four-hour window.

The current version doesn't have any food restrictions for the fueling period, but you're not supposed to eat at all during the fasting period. While this might sound similar to the popular IF diet known as the 16:8 diet, in which you fast for 16 hours and eat during an eight-hour period, it's actually very different. First, it's much easier to fit your daily calorie needs into eight hours instead of four, and in the Warrior Diet, you fast during the majority of the day, which is much more challenging than fasting overnight and into a short portion of the day, like you would with the 16:8 diet.

And it's different from the one-meal-a-day (OMAD) diet. The biggest difference is that the OMAD diet is simply one meal, while the traditional Warrior Diet allows a small amount of food during the day and a larger meal in the evening, explains Amber Pankonin, RD, the owner of the food blog the Stirlist. "Both diets are based on principles of intermittent fasting, which essentially restricts food intake for a period of time but allows you to consume food during a specific timeframe. However, the Warrior Diet does emphasize that the overfeeding window or eating period should be in the evening," she adds.

What can you eat on the Warrior Diet and what should you avoid?

That depends on which version of the diet you're following. The original Warrior Diet plan called for small meals of low-carb, naturally occurring foods such as eggs, dairy, and nuts, paired with high-nutrient carbohydrate sources such as fruits and vegetables throughout the day, says Totoro. The daytime underfeeding period was followed by mass quantities of high-protein and high-fat foods paired with whole grain and whole-food carbohydrate sources during the overfeeding period at night. The more modern take on the Warrior Diet allows you to eat whatever you want during your eating window.

"While the original diet stressed nutritious and naturally occurring foods even during the 'feast' stages, the more modern, 'free-for-all' mentality can lead to overeating high-fat foods that are often lacking in nutrients," says Totoro.

If you're still intrigued enough to try it, he recommends easing into a fasting period a few days a week to assess how your body responds.

Pankonin shares some guidelines for exactly what to eat during each period with the Warrior Diet as initially intended:

  • Foods to eat during the underfeeding period: According to Hofmekler, food during the underfeeding period should consist of "live" food, including fresh fruits, vegetables, and a small amount of protein. He does not recommend consuming grains or breads, processed juices, or cooking methods using heat or pasteurization.
  • Foods to eat during the overfeeding period: Fresh foods like fruits and vegetables are still encouraged, but Hofmekler says you can now have "cooked, warm food." The meal should start with green, leafy vegetables and then continue with protein-rich foods like fish and beans. Finally, you can wrap it up with a carbohydrate source, such as quinoa or nuts and seeds.

As for alcohol, Pankonin notes that wine is allowed before, with, or after dinner, and that Hofmekler believes wine is good for protein digestion and might be helpful when consuming the evening meal.

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So, are there any health benefits to the Warrior Diet?

Because many people consume fewer calories than they normally would by only eating during a small window with this diet, this may result in weight loss over time, Totoro says. While research has shown that any IF regimen can help people lose weight, there's no scientific evidence at this point to support the Warrior Diet specifically as an effective method for weight loss. And because the diet is so extreme, it may not be sustainable for many people.

Additionally, any evidence of potential health benefits related to the Warrior Diet is more based on the benefits of intermittent fasting in general, he says.

"With IF, there's emerging evidence that for some people, shrinking the eating window may help with GI issues, blood sugar control, inflammation, and other conditions," says Totoro. "But it's important to remember that everyone responds differently to fueling and activity, and what works for some will not work for others." It's also worth noting that a lot of the research on IF is done in mice, not humans, so it's not entirely clear how the benefits observed in mice translate to humans.

What does a sample Warrior Diet meal plan look like?

If you are still interested in trying the Warrior Diet, here is a three-day meal plan from Pankonin to get you started.

Day 1

  • Breakfast: One cup of water with lemon, one cup of black coffee with a dash of milk, 4 oz freshly made carrot juice
  • Lunch: One apple, 4 oz plain Greek yogurt
  • Snacks: ½ cup of blueberries
  • Dinner: A green salad with a small amount of oil or salad dressing, steamed carrots, quinoa, raw nuts

Day 2

  • Breakfast: One cup of water with lemon, one cup of black coffee with a dash of milk, 4 oz freshly made orange juice with ginger
  • Lunch: One kiwi, one poached egg, one cup of fresh broccoli
  • Snacks: ½ cup of raspberries, 4 oz protein shake made with organic milk
  • Dinner: A green salad with a small amount of oil or salad dressing, steamed broccoli, 4 oz poached fish with barley

Day 3

  • Breakfast: One cup of black coffee with a dash of milk, 4 oz freshly made mango or papaya juice
  • Lunch: Half a grapefruit, 4 oz cottage cheese, 1 oz raw almonds
  • Snacks: ½ cup of strawberries
  • Dinner: A green salad with a small amount of oil or salad dressing, fish soup, steamed zucchini, beans, and brown rice

What do people who tried the Warrior Diet have to say about it?

Jaymi Prieto, 36, who has been doing the Warrior Diet for about three months, tells Women's Health, "So far I've lost 20 pounds. Fasting has made me feel better overall. I'm able to stay motivated by tracking my progress through pictures and measurements. I only wish I had started this journey sooner."

warrior diet review

Jaymi Prieto

Kristen Ward, 39, found the Warrior Diet to be easy once she eased herself into it by starting with 14:10, 16:8, and increasing to 20:4, and she would definitely recommend it to her friends. "I have never felt better in my life, and many of my health ailments I was battling have resolved. I have lost a total of 105 pounds since starting my journey. When it comes to what contributed to my success, I would have to say setting attainable goals that can be adjusted at any time, perseverance, and embracing personal accountability while giving myself grace to make mistakes and learn from them," she says.

warrior diet review

Kristen Ward

Kelsey Pillischer, who tried the diet for Women's Health for more than two weeks, says, "I don't recommend dieting during your period, but ultimately, I lost four pounds in spite of that hormonal derailment. While I don't think I could stay on this diet for too much longer, it was a good way to reset healthy habits like calorie counting and regular weigh-ins."

What are the downsides of the Warrior Diet that I should know about?

Despite the glowing reviews, the Warrior Diet is restrictive and pretty extreme, which means it could lead to disordered eating habits for some people, says Amanda A. Kostro Miller, RD, a registered dietitian and advisory board member at Fitter Living. "This diet promotes binge eating during the four-hour non-fasting period, which can lead to stomach distension, exacerbation of heartburn, and many other GI symptoms," she explains. "Some at-risk people may become obsessive about the binge session and engage in harmful behaviors like purging to remedy feeling too full."

Like any form of IF, you may also experience feelings of fatigue and hunger during the fasting period, which are signs it probably isn't a good fit for you.

Pankonin would not recommend the Warrior Diet because it is restrictive and could be harmful both physically and psychologically, especially if somebody has a history of disordered eating or an eating disorder.

Who should and shouldn't try th e Warrior Diet?

This type of diet isn't sustainable for an extended period of time, so it's probably not a good idea for anyone, really. But it's particularly dangerous for people who take medications with food or that are time-released, says Totoro. People with diabetes should also be extra cautious since this type of diet could mess with your blood sugar.

Athletes who are training at a high or very competitive level should consult with their coaches and health care providers before attempting this diet as well, he adds.

Lastly, pregnant women, children, and people who have been diagnosed with eating disorders or dealt with disordered eating in the past shouldn't try this diet, says Kostro Miller.

The bottom line: The Warrior Diet is extremely restrictive, and while it may lead to weight loss, it's likely not sustainable. Consult with a dietitian or health care provider before trying this diet.