How does the 5:2 diet work?

A recent analysis of many weight loss studies concluded that overall calorie reduction is the most important factor in weight loss, rather than the actual composition of the diet. The 5:2 diet reduces your weekly calorie intake by 25%, while requiring you to diet for only 2 days a week. You eat normally for 5 days and fast on the other 2 days.

The main advantage of the 5:2 diet is that you are not dieting all of the time. With only 2 days of restriction you can achieve a significant reduction in overall calories, whilst being flexible with food choices 5 days a week. Fasting days don’t have to be consecutive, and you can change your 2 fasting days each week to fit in with your schedule and social engagements.

What are my calorie limits?


*Specific requirements for a normal day vary from person to person, based on height, weight, age & activity level.


When prompted, please select ‘maintain weight’ as your weight goal to calculate your calorie requirements for a normal day.

What are the benefits of the 5:2 diet?

Many diets can be frustratingly difficult to follow, particularly if they restrict you to only a small number of foods, or cut out major food groups such as fat or starchy carbohydrate (e.g. bread, rice, pasta). Whether you have struggled with other diets that haven’t worked, or are trying to lose weight for the first time, the 5:2 approach offers an alternative, easy-to-follow solution.

The 5:2 method is based on scientific research and there is a growing body of evidence to show that following the 5:2 diet offers many benefits. Reducing calories for only 2 days a week is easier for some people than traditional dieting for all 7 days. Fasting for 2 days a week can also help you understand portion control as, after 2 days of eating small amounts of food, people often realise that their usual portion sizes on non-fasting days are too large.

In addition, restricting your intake for only 2 days a week can lead to better insulin function, reduced cholesterol levels and fat loss rather than muscle loss. Intermittent fasting may also lead to greater reductions in insulin within the body, which has been linked to a lower risk of breast cancer. Additionally, fasting appears to help the body repair itself, which may slow the ageing process and prevent age-related mental deterioration.

What can I eat on the 2 fast days?

Everyone is different; some people like to split their food intake on fasting days into 2 meals and 2 snacks, others like to have one larger meal a day – you know yourself best. Sometimes it takes a few fasting days to work out the most suitable plan for you.

Foods that are good to include on fasting days are lean protein (e.g. meat, fish, eggs, tofu), low-fat and low-sugar dairy foods (e.g. skimmed milk, low-fat natural yogurt, cottage cheese), small amounts of healthy fats (e.g. almond butter, peanut butter, olive oil), vegetables and fruit.

You may be thinking ‘What about carbs?’. It is best to restrict carbohydrates, as they can make you more hungry.

Calorie combinations on fasting days


It’s a good idea to eat plenty of protein as it has been scientifically proven to keep you feeling fuller for longer. Lots of vegetables can be included on your fast days as they are often very low in calories and high in nutrients. Salads are a great way to fill up your plate, while keeping within your calorie budget.

Top tips for fasting days

  • Your fluid requirements are higher on a fast day, so drink more calorie-free fluids than normal. Aim for 3 litres on a fasting day. Water, herbal tea and sugar-free squash make great choices.
  • Alcoholic drinks have little or no nutritional value and should be avoided on fasting days. Alcohol can make you feel more hungry and lead to a higher calorie intake than you had planned!
  • Protein is very filling, so should be included where possible. Chicken, turkey, fish, pulses and beans are examples of high-protein, low-calorie options.
  • Fill up on salad and vegetables as they are very low in calories.

What can I eat on the 5 non-fasting days?

The key to long term success when following the 5:2 diet is to maintain a balanced diet on your non-fast days. This ensures the hard work you put in is not wasted, and means you get a wide range of nutrients and vitamins. To achieve a balanced intake, include foods from all the main food groups:


One criticism of the 5:2 diet is that people do not always eat healthily on non-fast days. It is important to be aware of your recommended calorie limits on a normal day (see table on page 5). Use this book to help you understand calories in food and drinks, as overeating and having high-calorie items (e.g. take-away meals & alcohol) can easily take you over your recommended calories.

Top tips for non-fasting days

  • Eat healthily 5 days a week, 3 meals a day. Balance is key.
  • Snacks between meals should be healthy; yogurt and fruit are perfect as they are naturally low in calories and fat.
  • Be mindful – is the food you are eating nourishing or junk food? Is the portion size right? Are you eating when you are full? Are you eating for reasons other than hunger?
  • Try to cook foods yourself and cut down on processed foods.
  • Allow yourself a treat, but avoid bingeing.
  • Try to be active on your non-fasting days: walk to the shops, take the kids to the park or get out in the garden; it all counts. Consider how you can reduce the amount of sitting time each day, such as watching TV and time in front of a computer. Moving more will burn more calories.

Can anyone follow the 5:2 diet?

Measuring your Body Mass Index (BMI) is a good way to see if you need to lose weight. If you have a BMI higher than 25, the 5:2 diet could help you to achieve a healthy weight.


There are some people who should not follow the 5:2 diet; it is not recommended for those who are pregnant, breastfeeding or have an eating disorder. It is also unsuitable for children and adolescents. Approach your healthcare team for advice if you have low blood pressure, diabetes, kidney disease or depression.

Dietary restriction, of any type, can lead to nutritional deficiencies. Nutrients that you may lack on fasting days include calcium, iron and fibre. Take particular care to eat balanced meals and include sources of these nutrients on your non-fast days.