Today, 63% of all UK adults are classed as overweight or obese – the equivalent of around 35 million people. And 43% say they’re trying to lose weight, with thousands of daily online searches for quick-fix weight loss solutions.

But, the truth is that healthy and sustainable weight loss will never come from quick-fix diets. Instead, it’s much better to focus on developing healthy lifestyle habits that you can realistically follow in the long-term.

One trend that claims to do this is the 5:2 diet, which is based on the concept of intermittent fasting. Here, we’ll explore everything to do with the 5:2 diet: including what it’s all about and whether it really works.

What is the 5:2 diet?

What is the 5:2 diet?

The 5:2 diet is centered around the practice of intermittent fasting for weight loss. It first became popular in 2013 when former doctor and British television journalist Michael Mosley wrote his bestseller The Fast Diet. Mosley outlined the idea that eating normally for most of the week and restricting for the rest, was an effective weight-loss method.

People on the 5:2 diet eat the recommended amount of calories for their height and weight for five days a week, but reduce their calorie intake to a quarter of their daily needs for the two other days. According to 5:2 diet guidance, this equates to around 500 calories a day for women, and 600 for men.

Not only does it place severe restrictions on what people can and can’t eat (which can be problematic in itself), the diet also fails to account for the various factors that impact an individual’s caloric needs. This includes everything from weight and height to activity levels.

What does following the 5:2 diet involve?

What does following the 5:2 diet involve?

People on the 5:2 diet can decide which days of the week they eat normally and which they restrict on. Though, many people tend to favour fasting on Mondays and Thursdays, and eating at their maintenance level for the rest of the week.

When fasting on the 5:2 diet, people will sometimes eat two to three small meals a day, or skip breakfast in order to have two slightly larger meals later on. Though, guidance recommends spacing out your food as much as possible. And while ‘normal’ eating days are free from restriction, people are still encouraged to choose a healthy range of whole foods like vegetables, whole grains, healthy fats, and lean protein.

If you do decide to follow the 5:2 diet, it’s important to recognise that ‘eating normally’ doesn’t mean eating huge amounts of whatever you like on non-fasting days. Not only can this affect your ability to lose weight, but getting into a pattern of restriction followed by overindulgence isn’t healthy and can have a negative impact on your relationship with food.

What are the benefits of the 5:2 diet?

What are the benefits of the 5:2 diet?

According to research, there may be some potential benefits to the 5:2 diet. For example…

It can result in weight loss

Research has shown that the 5:2 diet can lead to similar weight loss results to other calorie-restricted diets, without people having to feel they’re restricting the whole time.

It’s flexible

People on the 5:2 diet can choose their fasting days based on their own schedule. As a result, many people find it easier to follow than other diets which require continuous calorie restriction and find comfort in the ability to have five ‘normal eating days’ a week.

There are also no forbidden foods. So long as you stick to the recommended calorie intake, technically no foods are off-limits.

It may be beneficial for managing diabetes

Various studies suggest that the intermittent fasting technique used in the 5:2 diet can significantly reduce insulin levels and improve insulin sensitivity. As a result, it may help those living with diabetes manage their symptoms.

It may offer other health benefits

There’s evidence that fasting methods such as those used in the 5:2 diet may help fight inflammation, improve cholesterol levels, and boost brain function.

What are the disadvantages of the 5:2 diet?

What are the disadvantages of the 5:2 diet?

While research finds some benefits to the 5:2 diet, there are many pitfalls to consider. These include…

High drop-out rate

Due to its restrictive nature, many people find the 5:2 diet difficult to sustain in the long-term. For example, this study found that around 38% of people gave up during a 5:2 diet trial period alone.

Risk of overindulging

It’s human nature to want to reward ourselves for our hard work – including when we successfully fast for a long period of time. Cutting back calories to just one quarter of your daily requirement is a severe restriction and can sometimes cause people to overindulge out of frustration. Not only can overindulging counteract weight loss results, but it can easily cause people to gain weight too.

Difficult to adjust to

Adhering to the 5:2 diet requires serious dedication, especially in the beginning. Many people struggle with severe hunger and other unpleasant side effects, like irritability and fatigue.

Can give way to unhealthy eating habits

In some cases, the restrictive nature of the 5:2 diet can give way to unhealthy eating habits and behaviours like binge eating, severe restriction, and food guilt.

Danger of deficiencies

With so little calories to play around with on fast days – and no limit on the amount of carbs and fats you consume – it’s near impossible to eat a healthy well-rounded diet.

Since most people cannot get their daily vitamin and mineral requirements from eating less than 1200 calories per day, research has shown that some of the greatest dangers of the 5:2 diet relate to vitamin and mineral deficiencies.

Who is the 5:2 diet suitable for?

Who is the 5:2 diet suitable for?

While the 5:2 can offer results for some people, it’s not suitable for everyone. Some people should avoid dietary restrictions and fasting methods entirely. These include…

  • People with an eating disorder, or history of disordered eating habits.

  • Pregnant women and women who are breastfeeding.

  • People who are underweight, malnourished, or known to have nutrient deficiencies.

  • Growing children and teenagers.

  • People who experience frequent drops in blood sugar levels.

  • Women who are trying to conceive or have fertility issues.

Does the 5:2 diet really work?

Does the 5:2 diet really work?

Put simply, if you eat less calories than your daily requirements, you’ll lose weight. And it’s true that many people who follow the 5:2 diet experience successful weight loss fairly quickly. However, as hinted at by Mosley’s title, The Fast Diet, there’s an important catch.

While the 5:2 diet may work for some people in the short-term, it’s rarely sustainable and can easily lead to unhealthy habits. As a result, research shows that even if you successfully drop weight with the 5:2 diet, the majority of people put the weight back on after reverting back to their ‘normal’ lifestyle.

After all, not many people can continuously live so restrictively – and why should they have to? The best diets aren’t actually ‘diets’ per say, but long-term lifestyle transformations centered on developing healthy habits like eating a balanced diet and exercising regularly.

Final thoughts...

It’s easy to want to opt for quick-fix strategies when it comes to losing weight. But it’s important to remember that achieving your weight loss goals should never be done at the expense of either your physical or mental health.

While popular diet trends like the 5:2 diet may be able to deliver fast results, they’re unlikely to be sustainable in the long-term. Instead, the best way to maintain your health, happiness, and weight loss results in the long-term is through simple lifestyle changes like eating a balanced diet and exercising regularly.

Remember, slow and steady wins the race; and never has that been more true than when it comes to achieving – and maintaining – a healthy weight.

For more information on how different diets work, you might be interested in reading our article 10 popular diets to try. For other ideas, visit the diet and nutrition section of our website.

What are your experiences of the 5:2 diet? Do you think it’s a sustainable method for weight loss? We’d be interested to hear about your experiences in the comments below.