Quick version
The 5:2 diet is a form of intermittent fasting in which you eat roughly as usual five days a week and significantly restrict your energy intake on two days. For some people, this can be a way to reduce overall energy intake and support weight loss.
Studies suggest that the 5:2 diet may contribute to weight loss and may also affect certain metabolic risk markers, such as blood lipids, blood pressure and blood sugar regulation. However, the effects vary between individuals, and the method has not clearly been shown to be more effective than other approaches that create a sustainable calorie deficit.
The 5:2 diet is not suitable for everyone. People who are pregnant or breastfeeding, have or have previously had an eating disorder, have diabetes, or take certain medications should consult a healthcare professional before starting intermittent fasting.
5:2 – intermittent fasting made simple
The 5:2 diet is a form of intermittent energy restriction used primarily for weight loss. The approach involves eating roughly as usual five days a week and significantly reducing your energy intake on two selected days.
For some people, this can be an easier way to create a calorie deficit than restricting energy intake every day. However, how well the method works depends mainly on your total energy intake over time, the types of foods you eat and whether the approach is sustainable in the long term.
What is the 5:2 diet?
With the 5:2 diet, you restrict your energy intake on two days each week. This does not usually mean complete fasting.
In the traditional version of the diet, energy intake on these days is often around 500–600 kilocalories, although individual needs vary. On the remaining five days, you eat more normally.
The idea is that the lower energy intake on fasting days reduces your total weekly energy intake. If you do not compensate by eating significantly more on the other days, this may contribute to weight loss.
How intermittent fasting works with the 5:2 method
When energy intake is significantly reduced, the body relies to a greater extent on stored energy reserves. During periods of low energy intake, insulin levels decrease and the body increases its use of stored fat as an energy source.
However, this does not mean that the 5:2 diet has been shown to provide unique health benefits compared with other weight-loss methods. Many of the improvements that may be seen in blood lipids, blood sugar and blood pressure are likely related to reduced energy intake and any resulting weight loss.
The fasting days do not need to be consecutive. Many people choose, for example, Monday and Thursday, as this can make the approach easier to follow.
Potential benefits of 5:2 fasting
Research shows that intermittent fasting may be an option for people who want to lose weight. However, results vary between studies, and the 5:2 diet has not clearly been shown to be more effective than other forms of calorie restriction.
Potential effects include:
- weight loss and reduced fat mass
- improvements in certain blood lipid levels
- improved markers of blood sugar regulation in some people
- lower blood pressure in some people with overweight or metabolic abnormalities
Research is also ongoing into how intermittent fasting affects processes such as inflammation and cellular mechanisms. However, the clinical significance of these effects is not yet fully understood.
How quickly results become noticeable varies. Changes in weight and metabolic markers are influenced by factors such as energy intake, physical activity, starting weight, diet composition and how consistently the method is followed.
What can you eat on fasting days?
Energy intake is significantly restricted on fasting days, which makes it especially important to choose foods that provide protein, fibre, vitamins and minerals.
Examples of suitable foods include:
- vegetables and vegetable soups
- eggs
- fish or other lean sources of protein
- quark or plain yoghurt
- legumes
- salads with vegetables and protein-rich ingredients
- water, coffee or tea without sugar
Protein-rich foods and fibre-rich vegetables may help improve satiety despite a low energy intake.
It is also important to drink enough fluids. If you become dizzy, very weak or feel clearly unwell, you should stop fasting and eat.
Frequently asked questions about the 5:2 diet
How quickly can you see results from 5:2?
This varies from person to person. If the 5:2 diet creates a sustained calorie deficit, weight loss may begin relatively early, but the rate depends on the size of the calorie deficit and how you eat during the rest of the week.
Long-term, sustainable change is more important than rapid results.
Can you exercise on fasting days?
Many people can exercise on days with restricted energy intake, although performance may be affected.
Low- to moderate-intensity exercise often works well. For more demanding strength or endurance training, it may be appropriate to adjust the intensity or schedule the most strenuous sessions on days when you eat normally.
Stop exercising if you feel dizzy, weak or unwell.
Is the 5:2 diet suitable for everyone?
No. Intermittent fasting is not suitable for everyone.
Particular caution is needed if you:
- are pregnant or breastfeeding
- have or have previously had an eating disorder
- have diabetes, especially if you use medicines that can cause low blood sugar
- are underweight or have unintentional weight loss
- use medicines that need to be taken with food
- have a medical condition where regular energy or nutrient intake is important
Children and adolescents should not use the 5:2 diet as a general weight-loss method without assessment by a healthcare professional.
If you have a chronic medical condition or take regular medication, it may be advisable to consult a doctor before starting intermittent fasting.
Can blood tests be relevant during weight loss?
There is no general medical need to take blood tests solely because you are starting the 5:2 diet. However, blood tests may be relevant for people who want a broader picture of their metabolic health or who have risk factors for conditions such as diabetes, cardiovascular disease or liver abnormalities.
If you make a major lifestyle change and lose weight at the same time, some blood values may change over time.
Markers that may be relevant to monitor
Blood lipids
LDL cholesterol, HDL cholesterol and triglycerides provide information about your blood lipid profile and are used, among other things, when assessing the risk of cardiovascular disease. Weight loss and changes in dietary habits can affect these values.
HbA1c and glucose
HbA1c reflects the average blood sugar level over a longer period and is used, among other things, in the investigation and monitoring of diabetes. Glucose shows the blood sugar level at the time the sample is taken.
These tests may be particularly relevant if you have risk factors for type 2 diabetes or have previously had elevated blood sugar levels.
Liver markers
ALT, AST and GGT may be relevant in cases such as overweight, metabolic abnormalities or suspected fatty liver disease. However, they do not need to be checked routinely solely because you are following the 5:2 diet.
Insulin
Fasting insulin can in some contexts provide additional information about insulin metabolism, but the result should be assessed together with other test results and clinical factors. A single insulin test cannot diagnose insulin resistance on its own.
When are vitamins and minerals relevant?
Vitamin D, iron, ferritin and vitamin B12 are not specific markers of how well the 5:2 diet is working.
However, these tests may be relevant if you have symptoms of a deficiency, follow a diet with limited nutritional variety or have other risk factors for vitamin or mineral deficiency.
If you want a broader picture of your health, you can order blood tests and health checks through Testmottagningen. Blood sampling is carried out at an affiliated testing centre and the results are made available digitally through the test result service.
All of the tests above can be ordered through us. Blood sampling is carried out at an affiliated testing centre of your choice, and your test results are made available digitally through the test result service.
