The 5:2 diet – what is it and does it really work? - Rest Less (2024)

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

But, the truth is that healthy and sustainable weight loss is a gradual process that results from developing healthy lifestyle habits that can be followed long-term.

One health trend that claims to offer weight loss results is the 5:2 diet, which we’ll explore here.

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

Following Mosley’s guidelines, the 5:2 diet recommends that people eat the number of calories suggested for their height and weight five days a week, and reduce their intake to a quarter of their daily calories for the remaining two days. According to 5:2 diet guidance, this equates to around 500 calories a day for women, and 600 for men.

From the get-go, it’s easy to see why the 5:2 diet is problematic, as it places severe restrictions on calorie intake and fails to account for the various factors that can impact how much a person needs to eat.

People on the 5:2 diet can choose which days of the week to eat normally and which to restrict on.

Many people favour fasting on Mondays and Thursdays, where they’ll 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.

On ‘normal’ eating days, people are still encouraged to base their diet around whole foods like fruit, vegetables, whole grains, healthy fats, and lean protein.

The 5:2 diet allows you to choose your fasting days, which many people find easier than other diets which require continuous calorie restriction.

Similarly, while eating mainly whole foods is encouraged, there aren’t any forbidden foods.

There’s evidence that intermittent fasting may help fight inflammation, improve cholesterol levels, and boost brain function.

Due to its restrictive nature, many people find the 5:2 diet difficult to sustain long-term. This means that while you may drop weight quickly, it’s likely that you’ll put it back on.

In this study, around 38% of people on the 5:2 diet gave up during a trial period alone.

It’s human nature to want to reward ourselves for our hard work – including when we successfully fast for a long period of time.

Restricting calories to just a quarter of your daily requirement is a severe restriction, and it’s common for people to overindulge afterwards.

With so little calories to play around with on fast days – and no limit on the amount of carbs and fats you can consume – it’s near impossible to eat a healthy well-rounded 5:2 diet.

As a result, research has shown that some of the greatest dangers of the 5:2 diet relate to vitamin and mineral deficiencies.

Experts advise that certain people should avoid the 5:2 entirely. This includes…

• 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

Put simply, if you eat fewer calories than you burn, 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 in Mosley’s title, The Fast Diet, there’s an important catch.

While the 5:2 diet may work initially for some people, it’s rarely sustainable long-term and can lead to unhealthy habits. In fact, research shows that even if you successfully drop weight with the 5:2 diet, you’re likely to put the weight back on after reverting to your ‘normal’ lifestyle.

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

Head over to the health and diet and nutrition sections of our website if you’d like more advice on this.

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 your physical or mental health.

While popular 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 a healthy weight is by making simple, healthy lifestyle changes.

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

Do you have any experience of the 5:2 diet? We’d be interested to hear from you in the comments below.