Intermittent fasting: is the 5:2 diet good for weight loss? 

Intermittent fasting involves eating much less food or no food at all at certain times of the day or week. The 5:2 diet is a popular form of intermittent fasting.

On the 5:2 diet, you eat a normal, healthy diet for 5 days of the week, and then ‘fast’ on the 2 remaining days by eating just 25 per cent of your normal energy (calorie) intake.

The recommended number of calories per day is 2,500 for men and 2,000 for women. So according to the 5:2 diet, men should aim for around 600 calories on fast days, and women should aim for 500.

This means you should end up consuming less calories than you use on the days you’re fasting, which is called a ‘calorie deficit’. Over time, this can help you lose weight.

However, it’s important not to overeat on the days you’re not fasting, as this will reduce or cancel out the deficit created on your fast days.

Other versions of the diet include the 4:3 diet, where you fast for 3 days of the week instead of 2.

What are the benefits of the 5:2 diet?

There are a few reasons why you may find the 5:2 diet a useful way to eat less calories.

Some people prefer only having to eat less on certain days of the week, instead of every day.

And unlike other, more restrictive diets, you do not have to cut out different types of food or food groups completely on the 5:2 diet.

It’s also relatively flexible – you can choose to fast on any 2 days of the week you prefer.

However, some people may feel more hungry, tired or irritable on fast days. It’s worth leaving at least 1 non-fasting day in between to manage these symptoms.

Does intermittent fasting help with weight loss?

Research suggests that the 5:2 diet may help people lose weight, at least in the short term. But it may not be any more effective than other forms of intermittent fasting or traditional low-calorie diets.

A 2025 study in the British Medical Journal (BMJ) reviewed 99 trials that lasted between 3 and 52 weeks with around 6,500 people living with excess weight or obesity to compare 3 different types of intermittent fasting with a continuous low-calorie diet and eating ‘normally’.

The 3 intermittent fasting diets involved were:

• Whole day fasting – eating a very low number of calories on certain days, such as the 5:2 diet.
• Alternative day fasting – eating a very low number of calories every other day.
• Time-restricted eating – only eating during a certain number of hours a day.

The study found that all 3 types of intermittent fasting and the continuous low-calorie diet lead to a small amount of weight loss compared to eating normally.

Only alternative day fasting was shown to be slightly more effective for weight loss than a continuous low-calorie diet, with people on the fasting diet losing on average 1.3kg more weight. But this was only seen in trials that lasted under 24 weeks.

However, there is a lack of long-term data into the effects of the 5:2 diet – none of the trials included in the BMJ review lasted longer than 1 year – so we do not know what impact following the fasting diet may have on people’s health over time.

Instead, it’s likely more sustainable to focus on eating a balanced diet every day, such as the Mediterranean diet.

This way of eating, which includes plenty of vegetables, fruits, beans, wholegrains and fish, has a large body of evidence that shows it can help people lose weight in the long term.

What foods are best when intermittent fasting?

Although you can eat ‘normally’ for most of the week on the 5:2 diet, it’s still important to eat a healthy diet on non-fasting days.

This means eating lots of whole foods, such as vegetables, fruit, wholegrains, pulses, fish, nuts and seeds, and cutting down on processed foods high in sugar, salt and saturated fat.

On fasting days, try to eat foods containing protein and fibre. This can help you feel fuller when you’re eating fewer calories.

• Read more about how to eat a healthy diet.

Who should not follow the 5:2 diet?

The 5:2 diet is generally safe for most healthy people. However, no type of intermittent fasting is suitable if:

• you have diabetes or experience low blood sugar levels
• you’re underweight
• you have a history of eating disorders
• you’re pregnant or breastfeeding
• you’re a child or teenager.

It’s also worth checking with your doctor before you start the 5:2 diet if you have any health condition or need to take medicines with food.

Dietitian approved 5:2 diet recipes

If you’re thinking of trying the 5:2 diet and looking for meals to have on fast days, why not try these heart-healthy recipes are low in calories:

• Oven-baked salmon with lemon and fresh herbs – 319 kcal per portion
• Mediterranean vegetable frittata – 252 kcal per portion
• Green minestrone soup – 143 kcal per portion
• Linguine with leeks and mushrooms – 310 kcal per portion 
• Turkey, leek and bean bake – 370 kcal per portion

Discover plenty more tasty recipes with our recipe finder.

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