The 5:2 Diet has been grabbing the headlines for the past decade or so, likely because this diet claims to offer weight loss, better diabetes control, and improved immunity.

what is fast diet

You are what you eat, so being conscious of your dietary choices is an essential aspect of living a healthy life. According to the Centre for Disease Control and Prevention (CDC), in 2020, the prevalence of dieting amongst U.S. adults was as high as 17.1%.

With all sorts of diet plans– Ketogenic Diet, Mediterranean Diet, Veganism, etc.– being popularized today, it could be overwhelming for you to pick the best diet for yourself. However, if you’re feeling lost in the endless list of Google search results or you’re just looking for a starting point, you’ve come to the right place!

We’ve got your back on knowing everything about the 5:2 Diet, its good, bad, and everything in between.

What Is The 5:2 Diet?

The 5:2 Diet, commonly called the Fast Diet, was developed and published by Michael Mosley, a British journalist with accreditation in Medicine. Michael Mosley initially found this diet plan particularly beneficial for diabetic patients to maintain normal blood sugar levels.

“I wrote the Blood Sugar Diet because, nearly four years ago, I was diagnosed as a type 2 diabetic. I was not particularly overweight, weighing about 86kgs, and I didn’t look particularly fat, but that was because a lot of the fat I was carrying was internal”—Michael Mosley via “the fast 800” website.

Nevertheless, people widely practice the 5:2 Diet (with great results) for various health reasons. Weight loss happens to be one of the main motivations besides reducing heartbeat irregularities and menopausal hot flares.

How Does The 5:2 Diet Work?

As the name suggests, the 5:2 Diet plan is divided into 5 and 2 days. For five days a week, you can eat as you normally would without any restrictions. If you’re craving a doughnut, go for it. If you want that new burger on the menu, go for it!

fast diet

However, for the remaining two days (fasting days), you’d have to cut down your calories to a quarter of your daily calorie requirement. For example, if your daily calorie intake requirement is 1750 calories, you’d only need about 438 calories. To make matters easier, many dieticians encourage following the general rule of 500 calories for females and 600 calories for males.

Moreover, people only have two meals on their fasting days compared to their usual three meals per day. Alternatively, some people opt to reduce their calorie intake by taking three meals but in small proportions. The essence of intermittent fasting is incorporated into the 5:2 diet to further accelerate the weight loss process.

Is The 5:2 Diet A Good Way To Lose Weight?

There have always been both positive and negative connotations attached to the practice of dieting. That said, dieting, when practiced carefully and healthily, undoubtedly brings good results. The same applies to the 5:2 Diet.

One of the primary advantages of this diet is that it’s very flexible and hence, can easily suit your lifestyle. The fasting days must not be next to each other, so you can slip in a fasting day in between any of your “normal” or “non-fasting” days.

The increased chance of long-term adherence to this diet subsequently increases one’s chance of losing weight over time. Therefore, by definition, the 5:2 Diet is an excellent way to reduce or maintain your weight in the ideal range. With this being said, though, fasting is not suitable for everyone.

What Can I Eat On A 500 Calorie Fast Day?

You’d honestly be surprised at what you can indulge in for 500 calories! Even a regular Mc Chicken burger from McDonald’s is just around 300 calories. Nonetheless, it doesn’t justify poor food decisions on fasting days.

The primary purpose of fasting days is to channel the energy usually used to break down food into other processes such as burning fats or resetting the body’s microbiome. Hence, you need to choose easily digestible food that still supplies sufficient nutrients. Lean protein, simple carbohydrates, and unsaturated fats are vital, so choosing cruciferous vegetables, fruits or lean meat over burgers is a wiser choice.

Water plays a significant role during fasting days. Not only does it keep you hydrated, but it also comes with zero calories.

In essence, eating below 500 calories might be a real challenge for some, and not so much so for others. Either way, it’s always best to choose those calories wisely is. Additionally, try to keep track of your calorie intake on fasting days.

A Good 5:2 Diet Meal Plan For You

To get you started, we have curated a simple meal plan for fasting days following the 5:2 Diet method for you. These meal plans are meant to guide you only, and they’re subjected to changes as per your requirements. The specified calories are approximations only.

For people without any dietary restrictions:

One poached egg (70 calories)
Low-sugar baked beans (70 calories)

Fat-free yogurt and plums (88 calories)
Air-fried mushrooms and tomato (55 calories)

2-3 cups of steamed broccoli with cheddar cheese (107-161 calories)
1 sweet potato (112 calories)

For vegetarians:

Unprocessed oats (152 calories)
Unsweetened orange juice (56 calories)

Fruit salad with light dressing (73 calories)
1 sweet potato (112 calories)

Tomato soup without cream (91 calories)
1 slice of brown bread (90 calories)

For vegans:

Apple granola cookies (146 calories)
Unflavored coffee (5 calories)

Dairy-free cocoa-flavored protein shake (211 calories)

Vegan Teriyaki Grilled Eggplant (173 calories)

Does The 5:2 Diet Work?

Results are subjective—what looks like a huge difference to you may be negligible to others. That’s why clearly defined scientific parameters are crucial to understanding the effectiveness of any health-related interventions. However, there’s still a lack of scientific research and concrete evidence associating the 5:2 Diet with weight loss.

In 2018, a 12-month long clinical trial was conducted with 137 adult type 2 diabetic patients comparing intermittent energy-restricted diet (i.e., 5:2 Diet) and continuous energy-restricted diet (i.e., calorie deficit diet).

This study went on to conclude that intermittent energy-restricted diets are as effective as the latter for blood sugar control. Despite that, the effects observed in terms of weight weren’t reported nor mentioned. So, it’s still too soon to promise the benefits of the 5:2 diet from a scientific point of view.

Nonetheless, more research studies are needed to understand the long-term effects of the 5:2 Diet plan. Luckily, as you’re reading this, a 112 participants large randomized clinical trial on the impact of the 5:2 Diet on weight loss and cardiovascular risk factors in obesity is underway.

What Are The Risks And Drawbacks Of The 5:2 Diet?

Almost everything in life is a double-edged sword. Thus, there is no doubt the 5:2 Diet comes with its share of negatives. Firstly, complaints of adverse effects are prevalent amongst 5:2 dieters (especially first-timers) during the fasting period.

  • Fatigue
  • Dizziness
  • Difficulty sleeping
  • Irritability
  • Constipation
side effects of fast diet

The drastic and sudden reduction in calorie intake could be contributing to these unpleasant effects. So it would be best if you were on the lookout for these effects during your first few weeks.

This diet plan also requires extensive meal planning to maximize your chances of following through the diet plan. More than often, meal plans don’t take unforeseen events into account.

For instance, if you’re having an impromptu catch-up with a friend on your fasting day, it’d be an uphill struggle for you to keep count of your calories. Croissants and pastries alone give you about 600 calories! That said, some may find difficulty in keeping up with the 5:2 diet plan for the long run.

Finally, the 5:2 Diet is also not suitable for certain groups of people, such as:

  • Pregnant or breastfeeding women
  • Individuals with a history of eating disorders
  • Children or teenagers
  • Underweight individuals
  • People in high-stress jobs
  • Individuals with Type 1 Diabetes

Bottomline: 5:2 Diet

Finding the proper diet, right kinds of food, and meals won’t happen overnight. Learn to experiment with your diet now and then, discover yourself and always remember to embrace your health journey. The 5:2 Diet is less extreme and generally easier to maintain compared to stricter methods such as the 20:4 fast.

However, before trying to drastically change your diet, it’s best to consult your health professional to find out if it’s safe and suitable for you. This is especially so if you are pregnant or breastfeeding, taking any medications, and have any medical conditions.

Disclaimer: This article is only a guide. It does not substitute the advice given by your own healthcare professional. Before making any health-related decision, consult your healthcare professional.

Editorial References And Fact-Checking
  • Carter S, Clifton PM, Keogh JB. Effect of Intermittent Compared With Continuous Energy Restricted Diet on Glycemic Control in Patients With Type 2 Diabetes: A Randomized Noninferiority Trial. JAMA Netw Open. 2018;1(3):e180756. doi:10.1001/jamanetworkopen.2018.0756
  • Scholtens, E. L., Krebs, J. D., Corley, B. T., & Hall, R. M. (2020). Intermittent fasting 5:2 diet: What is the macronutrient and micronutrient intake and composition? Clinical Nutrition, 39(11), 3354–3360.
  • Harvie, M., Wright, C., Pegington, M., McMullan, D., Mitchell, E., Martin, B., … Howell, A. (2013). The effect of intermittent energy and carbohydrate restriction v. daily energy restriction on weight loss and metabolic disease risk markers in overweight women. British Journal of Nutrition, 110(8), 1534–1547. Retrieved from
  • Centers for Disease Control and Prevention. (2021). Products – Data Briefs – Number 389 – November 2020.Retrieved from
  • Michael, M. (2019). How your diet can help prevent cancer and dementia. Retrieved from The Fast 800 website:
  • Eat This Much, Inc. (2021). Eat This Much, your personal diet assistant. Retrieved July 12, 2021, from Eat This Much website:


  • Irshika Suthakar, B.Pharm

    Irshika is a Bachelor of Pharmacy (B.Pharm) graduate who enjoys crafting in-depth health and wellness content. Her experience interacting with real-life patients during work has enabled her to pick up valuable communication skills, which translates into well-written and highly-engaging content for her readers. Being a health content writer is what she considers a huge privilege because she loves empowering people to make informed health choices. LinkedIn


Irshika is a Bachelor of Pharmacy (B.Pharm) graduate who enjoys crafting in-depth health and wellness content. Her experience interacting with real-life patients during work has enabled her to pick up valuable communication skills, which translates into well-written and highly-engaging content for her readers. Being a health content writer is what she considers a huge privilege because she loves empowering people to make informed health choices. LinkedIn