The 5:2 diet involves eating what you want for five days of the week, and then restricting your calorie intake on the other two days.

It is also known as the intermittent fasting (IF) diet, and can have benefits for people with type 2 diabetes and prediabetes.

Due to the flexibility of the 5:2 diet, it is becoming more and more popular as there are no restrictions of the types of food you can eat.

How does the 5:2 diet work?

The 5:2 diet was developed in the UK, first by a dieting community before Michael Mosley, a medical journalist, hailed the promise of the diet.

The short periods of fasting help with weight loss, while prompting the body to repair damage without entering a starvation mode that conserves energy.

During the five days of the week, the daily calorie intake advised for people of a healthy weight is:

  • For men: 2,500 kcal per day
  • For women: 2,000 kcal per day

On the two fasting days, you are allowed to consume roughly 25 per cent of the values above. This is equal to:

  • For men: 600 kcal
  • For women: 500 kcal

You can take your two fasting days at any time of the week, but they must not be taken consecutively.

What science is behind the diet?

Short-term clinical studies have shown promising results for the fasting diet – it can help with losing weight and also reduce insulin resistance, hence its benefit to people with type 2 diabetes or prediabetes.

However, no long-term studies have established the safety or long term effectiveness of the 5:2 diet, with most previous studies tending to last under a year.

What are the benefits of the 5:2 diet?

While the 5:2 diet is largely similar to other calorie-restricted diets, it is said to be easier to follow than traditional calorie restriction.

Among the benefits reported from short-term studies of the 5:2 diet include:

  • Weight loss
  • Reduced insulin resistance
  • Decreased levels of LDL cholesterol and triglycerides
  • Reduced risk of heart disease, stroke and cancer
  • Reduced blood pressure

What are the disadvantages of the 5:2 diet?

Some can report finding the fasting days hard due to a lack of energy, while side effects can include headaches and dizziness. Increased hunger cravings can be experienced on these days.

Ensuring you eat as many nutrients as possible on the days in which you are not fasting is advised if you find you are struggling with the diet.

Can people with diabetes try the 5:2 diet?

Anyone with diabetes that is thinking of taking on the 5:2 diet should consult their diabetes specialist. Making dramatic changes to your diet can affect your blood glucose levels and impact your medication.

Hypo-causing medication

If your diabetes is treated with insulin, or other hypo-causing medication, such as sulfonylureas or glinides, you could be at an increased risk of hypoglycemia from the 5:2 diet.

Type 1 diabetes

Intermittent fasting could affect blood glucose levels of people with type 1 diabetes. If your health care team allow you to start the 5:2 diet, you may be required to check your blood glucose levels more often, particularly on fasting days and the next day after fasting days.

Type 2 diabetes

Improved insulin sensitivity is reported from the 5:2 diet, which is useful for people with type 2 diabetes, prediabetes and those with a BMI over 25.

As the body is forced to use stored energy – fat and stored glycogen – during the two fasting days, this can improve blood glucose levels and assist weight loss.

What can you eat?

There are no restrictions on what types of food you can eat on the non-fasting days, but it is best to follow basic healthy eating rules. These include limiting processed foods and ensuring you eat plenty of vegetables.

During the fasting days, you will need to stick to meals that are low in carbohydrate and fat on fasting days in order to keep to the 500 or 600 calorie counts on these days.

Among the foods you can eat on the 5:2 diet include:

  • Eggs (65 kcal per medium egg)
  • Non-battered white fish (135 kcal per 100g)
  • Grilled chicken breast without the skin (190 kcal per 100g)
  • Prawns (105 kcal per 100g)

Vegetables tend to be low calorie but if you need very low calorie vegetables, the following vegetables are particularly good options:

  • Celery (20 kcal per 100g)
  • Cucumber (15 kcal per 100g)
  • Bell pepper (26 kcal per 100g)