The Ultimate Guide To 5/2 Intermittent Fasting

Al Feky September 1, 2021

5/2 intermittent fasting, also known as the Fast Diet, is a powerful diet that is great for weight loss and overall health.

And if you’re looking to learn more about it, well, you came to the right spot.

The 5:2 fasting is one of the easiest IF protocols (also called The Fast Diet) during which you eat for five days and fast for two—and the research backs it.The 5:2 fasting is one of the easiest IF protocols, also called The Fast Diet, during which you eat for five days and fast for two. Medical doctors [1], scientists [2], fitness trainers, and media celebrities [3] follow and recommend it—and in this in-depth guide I wrote below (after 22 hours of research… not kidding), you’re going to see why.

Intermittent Fasting Protocols In Comparison

18:65:220:4 OMADAlternate Day
Fasting
What is it?18 hrs fasting
6 hrs eating
repeat daily
5 days eat normally,
2 days eat 75% fewer calories
One Meal A Day
20 hours fasting
Eat 1 meal in remaining 4 hrs
Day 1: eat normally,
Day2: fast, repeat
LevelBeginnerBeginnerAdvancedAdvanced
For whom?Changing lifestyle, healthy gradual fat lossSuitable for working parentsBoosting energy & quick weight-lossAthletes with alternate intense training days
Meals to skip1 Meal/DayVariable2 Meals/DayVariable
Calories/ dayNormal Intake (2000 Calories)5 Days Normal, 2 Days 75% LessLess Than NormalVariable
Weight-loss impactModerateModerateHighestHigh

In this article, you’ll learn the following:

  • What the 5:2 diet is, and how is it different from other IF protocols.
  • How to perform 5:2 works, what to eat and drink. 
  • Does a 5:2 protocol help with weight loss?
  • Is it safe to follow a 5:2 protocol, and can you keep exercising while doing it?


What Is The 5:2 Diet?

5:2 fasting. It’s pretty simple: you eat for 5 days and fast for 2. 

This means that for five days of the week, you get to eat normally; you don’t constrict when and how much you eat. 

And for only two days of the week, you fast by constricting your calorie intake to 25% of your total daily intake. On average, this is about 500-600 calories per day. 

The good news is that the 2 fasting days should not be consecutive and should be separated by at least 1 non-fasting day. 

Some would add to the challenge by doing a complete fast (0 calories) during their fasting days.

The protocol’s ultimate goal is to regularly eliminate 3000 Calories out of your weekly intake, which is about 21% of your “normal” needs. 

The Fast Diet, or the 5:2 diet, has helped many people lose weight fast and steadily.

In addition to weight loss, the 5:2 plan has multiple health benefits to offer, such as:

  • Reduces insulin and glucose (sugar) levels [4]. 
  • Protects from cardiovascular diseases [5, 6].
  • Lowers blood pressure [7, 8].


What Can I Eat?

What Can I Eat?

On Regular Days 

You can eat whatever and whenever you want, but remember to try to maintain a healthy balanced diet for optimal benefits. 

Binge-eating and having junk food on the regular may not help you in your 5:2 journey. 

There is no point in the whole thing if you intend to overeat during your five non-fasting days. You don’t have to be counting calories, but make sure not to exceed an average of 2000 calories often during the eating days.

On Fasting Days

Because of the high-calorie restriction, you are left with 500-600 calories to have during a “fasting” day. 

Here is how some people usually do it:

  • Three small meals
  • Two meals
  • One big meal

It really is flexible and customizable.

If your family situation or lifestyle demands three meals a day, you can have three (tiny) meals taking small bites in breakfast, lunch, and dinner. 

You may also divide the calories throughout the day as snacks. 

I am not a fan of snacking. My personal strategy is to get one big satisfying meal a day—one way to mix a 5:2 fasting with a 20:4 fasting (One Meal A Day). I forget about eating most of the day, and when I eat, I eat properly and avoid the torture of tiny bites. 

The only way to find what works best for you is to experiment. 

Here is a list of low-calorie food you can eat:

  • Cauliflower rice: is a great alternative to rice, as 1 cup of cauliflower rice is only 25 calories.
  • Vegetables: Most vegetables are low in calories. Per 1 cup, lettuce has only 5 calories. Cucumbers have 16, and cabbage has 22 calories. Salads will help you stay below your calorie limit and are easy to make.
  • Eggs: boiled or poached eggs are below 100 calories.
  • Lean fish: high in protein and low in calories, fish such as cod and salmon are great for fasting days.
  • Soups: soups are great for a low-calorie meal.


Will 5:2 Intermittent Fasting Help Me Lose Weight?

Yes! 

And here is why: when we are well-fed, sugar is the primary source of energy in our body, but when we fast, the sugar levels drop, which forces our body to use its storage of fatty acid. 

This is called the “fed-fast” cycle [5]. 

Almost all studies on the various types of IF have shown that people following such plans have lost body and fat mass [7, 8].

Additionally, regularly eating for 5 days and cutting off your calorie intake by 75% for 2 days of the week, reducing your total calorie intake per month by about 12,000 calories.

It is the same principle as any diet that requires calorie reduction, but instead of reducing your calorie intake every day, you do it in 2 days, which makes it intense and easier to follow. 

A lot of people swear by this diet for fast and steady weight loss, and those who cannot skip “common” meal times find it easier to follow than the 16:8 plan. 

But, as with all diet plans, it is recommended you follow a healthy balanced diet.

You won’t benefit from the 5:2 diet or any IF plan if you decide to have high-calorie food every day for the 5 non-fasting days. Same if you only eat high carbs and sweets as your only calorie intake on the fasting days.


Is 5:2 Intermittent Fasting Safe?

It is! 

Fasting, in general, has been practiced for thousands of years. It is perfectly safe for healthy young adults.

Nevertheless, you may experience some typical side effects during fasting days when you first start the diet, such as:

  • Hunger: an obvious side effect, but you would be surprised how quickly it will fade away. With time, you will get used to fasting days, but if you’re just starting, make sure to keep yourself busy to distract yourself from feeling hungry and drink lots and lots of water, tea, and other low-calorie drinks. 
  • Headaches: Eating small unbalanced meals can cause headaches, especially if you miss essential minerals; you may find yourself prone to hunger-induced headaches. Make sure you stay hydrated and have balanced food on fasting days. 
  • Mood swings: think of hangry (hungry+angry). 
  • Fatigue and lethargy: you might feel tired and lacking energy.

All of these symptoms are mild and restricted to the fasting days. They usually go away when your body and mind get used to fasting.

Can you exercise as usual on the fasting days? 

Absolutely yes. From my experience, and against the natural assumption, I find more energy on the fasting days in both weight-lifting and cardio. 

That said, you should yet approach that carefully.

I am not advising on your first ever fasting day to do high-intensity workouts for an hour. 

You should get your body first a chance to get used to that “healthy” lower-calorie intake, let it gradually learn to rely on your internal stores of energy. 

First when you feel comfortable with low-intensity exercises, start raising the bar until you reach the point when you feel the difference.

At that switch point, your body has started loving fasting and is more ready to exercise than on your regular eating days.

timferriss
@timferriss

In his acclaimed book “Tool of Titans”, Tim Ferriss, the American Entrepreneur and lifestyle guru, suggests walking and drinking as a key to master fasting. He grabs a cold liter of water with unsweetened lemon juice and a few pinches of salt and heads out for a brisk walk on his fasting days. 

From his experience, he prefers long walking for hours with tons of water over high-intensity weight training. 

Although the 5:2 diet plan is safe, it might not be for everyone. 

The following people should avoid it:

  • Pregnant and nursing women.
  • People with a history of eating disorders.
  • Diabetic people (if not supervised by medical doctors).


The bottom line

The 5/2 plan is a variation of IF that allows you to eat regularly for 5 days and fast for 2 days. 

Fasting days should not be consecutive, and you don’t starve yourself; you only restrict your calorie intake to 500-600 calories. 

While it might sound hard at first, you would be surprised at how quickly you’ll adjust to such a plan. 

You can opt for a low-calorie filling meal on fasting days to make your days easier. 

The 5:12 plan not only helps you lose weight fast, but also helps you learn how to control yourself and not let food control your life. 

All variations of intermittent fasting have been shown to help in losing weight. For a healthy adult, they are perfectly safe to follow.

The other protocols of IF are: 

  • The 24 hours fast: fasting entirely for 24 hours once a week. 
  • The 16:8 plan: fasting for 16 hours and eating for 8 hours.
  • Alternate day fasting: a cycle of fasting day followed by a non-fasting day.
  • The One Meal A Day protocol: fast for 20 hours and can eat for 4 hours.

Al Feky

Al Feky, M.SC (Masters of Science), is an absolute health nut with a passion for investigative writing, biohacking, and everything nutrition. When he is not writing, he likes to read, go swimming or bouldering, and plays tennis.

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