What Is the 5:2 Diet?

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In This Article

The 5:2 diet is an intermittent fasting method that involves reducing your food intake on two days of the week. You’ll eat normally for five days of the week, and on two days of your choice, you’ll eat very few calories. 

Intermittent fasting has proven health benefits, including weight loss and improved body composition , faster metabolism , brain health , and more. But the 5:2 is one of the more restrictive versions of intermittent fasting, and it may be difficult for some people to follow. 

In this article, you’ll learn how the 5:2 diet works, its benefits and risks, and what the experts say about this eating plan.

What Experts Say

“The 5:2 diet is one of the most popular intermittent diets and it’s likely you’ll lose weight while following it because you are reducing your overall calorie intake. It’s a highly regimented diet and can be hard to follow, especially on fasting days.”

Kelly Plowe, MS, RD

Background

Intermittent fasting has been around for decades — centuries, even — as a religious, spiritual, and political act. As far back as Ancient Greece, philosopher Pythagorous fasted and encouraged others to do so, as did Hippocrates and the Renaissance doctor Paracelsus.

Still today, major religions of the world fast during sacred times. Judaism, for example, observes several fasts throughout the year, while Christianity reserves a 40-day fast for the Lenten season. Political figures like Mahatma Gandhi and the civil rights Suffragettes have used fasting as a means of political protest.  

So you can see that fasting is nothing new — though the practice only recently became popular for health and fitness reasons. 

Following low-carb, paleo, keto, and commercial diet trends, intermittent fasting became the next big thing . Scientists, medical professionals, and entire health organizations have endorsed intermittent fasting for its beneficial outcomes on body weight, heart health, brain health, and more. 

There are several different ways to do intermittent fasting, including the Warrior Diet, the Fast Diet, water fasting, and more. This article covers the 5:2 form of intermittent fasting. 

How It Works

The 5:2 diet involves eating normally on five days of the week, and then restricting your caloric intake to only a few hundred calories on two days of the week. Most people who follow the 5:2 diet eat about 500-600 calories on their fasting days. 

What To Eat

You are generally free to eat whatever you want on the 5:2 diet. That’s one of the major appeals of intermittent fasting — there are no “good foods” or “bad foods.”

Instead of focusing on the content of foods (such as how many carbs or how much protein a food has), the 5:2 diet focuses largely on meal timing

That said, you should aim to consume nutritious foods on any eating plan. The 5:2 diet will work best if you fill up on vegetables, fruits, lean proteins, whole grains, and healthy fats. The healthy fats and protein are especially important on fasting days, as they’ll provide your brain and body with extended energy. 

On fasting days, you should also try to eat high-volume, low-calorie foods to fill up space in your stomach. Foods high in fiber, such as carrots and broccoli, are good choices that will keep you full. 

You can drink anything you want on your regular eating days, but on fasting days, you should stick to water in order to stay within that day’s calorie limit. 

Compliant Foods

  • Whole grains

  • Vegetables

  • Fruits

  • High-fiber foods

  • Healthy fats

  • Lean protein

  • Red meat

  • Beverages

Non-compliant Foods

  • Beverages other than water (on fasting days)

  • No foods are technically off-limits

Whole grains: Whole grains are rich in fiber and vitamins, and they help keep you full and satisfied. Carbohydrates are also great brain food, so whole-wheat breads, pastas, brown rice, quinoa and other delicious grains have a healthy place in the 5:2 diet. 

Vegetables: Broccoli, cauliflower, leafy greens, Brussels sprouts, sweet potatoes, squash — all these veggies and more are fair game on the 5:2 diet. Load your plate up with different colors to get in all the nutrients you need. 

Fruits: Fruit has a healthy place in any diet. You can enjoy citrus fruits, starchy fruits, berries, and more on the 5:2 diet. 

High-fiber foods: Beans, legumes, lentils, sprouted grains, oatmeal… These are all great high-fiber foods that will keep you full and provide your body with essential nutrients, especially on your fasting days.

Healthy fats: Be sure to include nuts, seeds, olive oil, avocados, oily fish, and other sources of omega-3s and omega-6s in your 5:2 diet plan. These will give your body energy when it runs out of glycogen stores

Lean protein: Foods like chicken breast, ground turkey, eggs, and fish can provide you with sustained energy and the protein your body needs for muscle growth and cellular repair. Try out these lean protein options for better health

Red meat: While it’s best to stick to lean protein most of the time, a few servings of red meat each week won’t hurt. Try incorporating lean ground beef or a lean cut of steak

Beverages: You can drink anything you want on your normal days, but it’s best to stick to zero-calorie beverages on your fasting days. Try to drink water, black coffee, and herbal tea on your low-calorie days. 

Recommended Timing

On five days of the week, eat as you normally would. This doesn’t mean you should eat more than usual — if you eat more on “normal” days to compensate for the lost calories on fasting days, you might not lose weight. And if you overeat high-calorie, high-sugar, or overly processed foods on your normal days, you may even gain weight. 

So try your best to keep your normal days normal.

On fasting days, you should experiment with timing to see what works best for your brain and body. Some people function best with a small breakfast, while others prefer to wait as long as possible to eat their first meal. 

Since you have a limited number of calories to work with (500-600), you should try to spread them out as much as possible. Eating high-volume foods will help with that. For example, if you’re trying to consume 500 calories on your fasting day, you could eat 200 calories at breakfast, 100 calories at lunch, and another 200 calories at dinner. You could also try eating 250 calories at lunch and 250 calories at dinner. 

As far as choosing the fasting days themselves, that’s entirely up to you. One common protocol consists of the following schedule: 

  • Sunday: normal
  • Monday: fast
  • Tuesday: normal
  • Wednesday: normal
  • Thursday: fast
  • Friday: normal
  • Saturday: normal

Resources and Tips

There’s a good chance you’ll experience side effects on fasting days if you’ve never tried fasting before. Side effects of fasting include:

  • Hunger
  • Headaches
  • Irritability
  • Fatigue
  • Trouble focusing
  • Loss of productivity
  • Sleepiness 
  • Mood swings
  • Nausea 
  • Weakness

These side effects are normal, usually minor, and typically go away once your body becomes used to fasting. If you feel overwhelmed with hunger, irritability, or any of the other side effects, try helping them pass with these tactics: 

  • Drink more water
  • Take a nap
  • Stay busy with work or errands 
  • Take a stretch break 
  • Take a shower or bath
  • Meditate 
  • Call a friend

Most of these fasting side effects will go away if you just stop focusing on them. Over time, your body should become used to fasting. 

Modifications

It’s definitely not easy to shift from eating normally every day to eating only 500-600 calories on two days. Instead of taking such a big leap, you can try slowly reducing your calorie consumption on fasting days. For example, during the first week, reduce your intake from 2,000 calories to 1,500 calories. The next week, try eating just 1,000 calories. Keep reducing in smaller increments until you’re eating the recommended 500-600 calories on fasting days. 

Pros and Cons

All eating plans and diets come with a unique set of pros and cons. Here are some goods and bads you can expect on the 5:2 diet. 

Pros

  • No foods are off-limits

  • You get to choose your fasting days

  • Intermittent fasting has proven health benefits

  • Sustainable once in the habit

Cons

  • Hard to start

  • Possibility of over-eating

  • Hunger and other side effects

  • Not ideal for all populations

Pros

No foods are off-limits: Many people like intermittent fasting because, despite having to restrict calorie intake, it helps them break free from a diet mentality. If you’ve struggled with food restriction in the past, or labeling foods as “good” and “bad,” the 5:2 diet might help you welcome new foods into your eating plan. By focusing on the time of eating, rather than the eating itself, you might find it easier to make healthy choices. 

You get to choose your fasting days: On the 5:2 diet, you’re free to choose your fasting days based off of your schedule. Most people choose to fast during the week, when it’s easier to stick to a routine. On weekends, you might find yourself at social events or family gatherings where it’s hard to stick to your fasting protocol.  

Intermittent fasting has proven health benefits: Clinical trials have shown fasting to aid in weight loss , lower blood sugar , improve insulin sensitivity, reduce bodily inflammation , and reduce the risk of cognitive disease . These are all fantastic health benefits that may make the 5:2 diet worth following. 

Sustainable once in the habit: Dropping your day’s calorie consumption from thousands of calories to hundreds of calories won’t be easy — at first. Some research suggests that intermittent fasting is easier for people to follow than daily calorie restriction, so it’s worth attempting if you are trying to lose weight long-term. 

Cons

Hard to start: Even though the 5:2 diet might be sustainable once you’re used to it, it requires some serious dedication in the beginning. You’ll deal with severe hunger and other side effects (more on that below) for the first fast, and possibly the first few fasts. Once you make it past the initial adverse effects, though, your body should adapt and you should feel fine. 

Possibility of over-eating: Restricting calories always presents the risk of over-eating. You may feel so hungry after your fasting days that you intentionally or unintentionally eat more than you need the next day. Not only can this result in the unpleasant side effects of over-eating, but you may not reach your health or weight loss goals. 

Hunger and other side effects: As mentioned earlier, you’ll likely experience side effects when you start the 5:2 diet. These side effects include severe hunger, fatigue, weakness, headaches, irritability, mood swings, feeling cold, trouble focusing, and difficulty falling asleep. 

Not ideal for all populations: The 5:2 diet (and intermittent fasting in general) isn’t for everyone. Some people should avoid the 5:2 diet, including those who: 

  • Have battled an eating disorder or disordered eating
  • Are pregnant
  • Are actively growing, such as pre-teens and teenagers
  • Have nutrient deficiencies, such as iron-deficient anemia
  • Are trying to conceive or have known fertility issues
  • Have hypoglycemia 
  • Have type 1 diabetes

How It Compares

When you’re shopping for an important product or service, you always check out the competition, right? Well, when you’re “shopping” for a diet or eating plan, you should make an effort to look at other similar diets. 

This section covers how the 5:2 diet compares to the federal dietary recommendations, as well as three other similar diets. 

USDA Recommendations

The federal dietary recommendations include five food groups: fruit, vegetables, grains, dairy, and protein. The key recommendations in the federal guidelines include:

  • “A variety of vegetables from all of the subgroups—dark green, red and orange, legumes (beans and peas), starchy, and other
  • Fruits, especially whole fruits
  • Grains, at least half of which are whole grains
  • Fat-free or low-fat dairy, including milk, yogurt, cheese, and/or fortified soy beverages
  • A variety of protein foods, including seafood, lean meats and poultry, eggs, legumes (beans and peas), and nuts, seeds, and soy products
  • Oils
  • Limited saturated fats, trans fats, added sugars and sodium”

Since the 5:2 diet doesn’t specify which foods you should and shouldn’t eat, your best bet is to plan your meals around the USDA recommendations. These guidelines are based off of decades of science, and they’re informed by some of the most experienced and trusted scientists and health professionals in the country. 

CALCULATOR

No matter what eating plan you follow, you must know how many calories you should be consuming each day in order to reach your weight goals. Ultimately, weight loss comes down to calories in versus calories out — you must eat fewer calories than you burn in order to lose weight.

Most people need around 2,000 calories per day, but women and children may need less, while men may need more. Very active people also usually need more than 2,000 calories. Factors that play a role in your calorie needs include: age, height, weight, genetics, occupating, and physical activity level.

Whether your goal is to lose, maintain, or gain weight, our Weight Loss Calorie Goal Calculator can help you determine your daily caloric needs. 

Similar Diets

The Warrior Diet: This intermittent fasting protocol involves fasting for 20 hours each day and eating all or most of your food within a 4-hour window in the evening. Learn more about the Warrior Diet

The 16:8 protocol: One of the most popular intermittent fasting methods, the 16:8 protocol involves consuming all of your calories for the day in an 8-hour window and fasting for the remaining 16 hours. This method works well for beginners because 16 hours is typically a doable fast, especially if you count your sleeping hours. 

Eat-Stop-Eat: On the Eat-Stop-Eat diet, you’ll observe a complete 24-hour fast once or twice a week. For example, if you stop eating at 8 p.m. on Sunday night, you wouldn't eat again until 8 p.m. on Monday night. Like the 5:2 diet, you’re free to choose your fasting days on the Eat-Stop-Eat diet.

Alternate-day fasting: This intermittent fasting protocol involves an ongoing cycle: Fast one day, eat normally the next, and so on. You can eat 500-600 calories on your fasting days on this diet. Ultimately, alternate-day fasting ends up as a 4:3 diet, versus the 5:2 diet.  

A Word From Verywell

Intermittent fasting is backed up by a lot of science. It may help you reach your weight, health, and fitness goals, but you should always be skeptical and cautious when considering diet plans. Make sure to thoroughly research the 5:2 diet before starting it, and always talk to a health professional if you have questions or concerns. 

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Article Sources

Verywell Fit uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read our editorial policy to learn more about how we fact-check and keep our content accurate, reliable, and trustworthy.
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Additional Reading

  • Barnosky AR, Hoddy KK, Unterman TG, Varady KA. Intermittent fasting vs daily calorie restriction for type 2 diabetes prevention: a review of human findings. Translational research: The Journal of Laboratory and Clinical Medicine. 2014;164(4):302-11.

  • Martin B, Mattson M, Maudsley S. Caloric restriction and intermittent fasting: Two potential diets for successful brain aging. Ageing Res Rev. 2006;5(3):332-353.

  •  St-Onge MP, Ard J, Baskin ML, Chiuve SE, Johnson HM, Kris-Etherton P, et al. Meal Timing and Frequency: Implications for Cardiovascular Disease Prevention: A Scientific Statement from the American Heart Association. Circulation. 2017;135(9):e96-e121.

  • Stote KS, Baer DJ, Spears K, et al. A controlled trial of reduced meal frequency without caloric restriction in healthy, normal-weight, middle-aged adults. Am J Clin Nutr. 2007;85(4):981-8.

  • Zauner C, Schneeweiss B, Kranz A, et al. Resting energy expenditure in short-term starvation is increased as a result of an increase in serum norepinephrine. Am J Clin Nutr. 2000;71(6):1511-1515.