Intermittent fasting explained

Would it not be perfect if a diet is not focused on food products and calories, but that it is more about when to eat something?

Intermittent fasting is a way of eating that focuses more on the time frame when something is eaten instead of what is eaten. In this diet, periods of eating alternate with periods of fasting (this means no food or less than 25% of the energy requirement). Naturally, people already do this during their sleep. With intermittent fasting, the fasting period is extended. The three most popular ways to do this are:

  • Fasting a couple of days per week (1-3 days), for 24 hours and eating normally the other days.
  • Fasting every other day. Fasting takes place every other day for 24 hours.
  • Fasting for a fixed number of hours per day. This is the most common variant and involves several consecutive hours of fasting per day. The hours can vary from a 16 to 20 hours fasting window with a 4 to 8 hour eating period. In daily life, this can, for example, be achieved by eating from noon until 8:00 pm, outside of which is the fasting period. This is also called time restricted fasting, where the time between noon and 8:00 pm is called the eating window.  


During the fasting period, it is possible to consume low-energy drinks such as water, coffee, and tea without added sugar or milk.

What are the claims surrounding intermittent fasting?

A quick search on the internet shows many different statements about intermittent fasting. Probably the most popular one is that it causes weight loss. In addition, intermittent fasting is said to improve insulin sensitivity, and increase the production of human growth hormone (HGH)]. There are also claims that intermittent fasting reduces the risk of type 2 diabetes, cancer, and Alzheimer’s disease. Moreover, it is beneficial to heart health because of a reduction in LDL cholesterol. 

So does the science behind intermittent fasting actually support these claims? The vast majority of studies have examined the impact of intermittent fasting on weight loss and the short term results appear to be similar to an energy restricted diet. There is some evidence that more muscle mass is lost using intermittent fasting. Several studies also show a beneficial health effect, whereby intermittent fasting may reduce total- and LDL cholesterol, triglycerides, and blood pressure which can reduce the risk of cardiovascular diseases. In addition, beneficial effects are seen on fasting blood glucose levels, HbA1c, and insulin, all of which play a role in diabetes. That all may sound very nice, but there are some comments to be made. The beneficial effects of intermittent fasting are comparable to those of normal weight loss. This may mean that the effect is not necessarily related to intermittent fasting per se, but to the result of weight loss because of a lower energy intake. Moreover, high-quality studies are lacking in some respects. 

 Apart from health effects, several studies show that intermittent fasting can reduce appetite. This can further contribute to reducing calorie intake, and thereby weight loss.


Who should try intermittent fasting?

Intermittent fasting is not for everyone, but it can be a good tool for weight loss. However, because it is more an eating habit than a diet, it is important to know how to still consume enough nutrients. There are also some limitations – for example, it can be difficult to apply intermittent fasting in social life. Moreover, it is less suitable for people who are underweight or have a past with eating disorders, as well as those with diabetes (type 1 or 2). In case of intensive sports, research is inconclusive. However, it is more likely that intermittent fasting has a neutral or negative effect on performance rather than a positive effect.


Intermittent fasting is a tool that can be used for weight loss. The health effects that result from this are most likely due to weight loss. By using intermittent fasting you lose as much weight as with a normal calorie restricted diet. It is important to make sure that you still get enough nutrients when applying intermittent fasting. Please refer to your dietitian if you want to try it out.

 Within Noory, it is currently possible to indicate the number of meals you want to eat per day. This can be set to three, these meals can be eaten within an eight-hour eating window for time restricted fasting. Using Noory like this will provide you with a sufficient amount of energy, and is therefore not suitable to lose weight. If that is something you prefer, it is advised to also select the energy restricted diet option, to ensure a calorie restriction.



  1. Cleveland Clinic. (2019). Intermittent Fasting: 4 Different Types Explained. Consulted on 25 May 2021, from: ttps:// 
  2. Healthline. (2019). 10 Evidence-Based Health Benefits of Intermittent Fasting. Consulted on 25 May 2021, from: 
  3. Diet doctor. (n.d.). Intermittent fasting for beginners. Consulted on 25 May 2021, from: 
  4. Harris, L., Hamilton, S., Azevedo, L. B., Olajide, J., De Brún, C., Waller, G., … & Ells, L. (2018). Intermittent fasting interventions for treatment of overweight and obesity in adults: a systematic review and meta-analysis. JBI Evidence Synthesis, 16(2), 507-547.
  5. Roman, Y. M., Dominguez, M. C., Easow, T. M., Pasupuleti, V., White, C. M., & Hernandez, A. V. (2019). Effects of intermittent versus continuous dieting on weight and body composition in obese and overweight people: a systematic review and meta-analysis of randomized controlled trials. International Journal of Obesity, 43(10), 2017-2027.
  6. Meng, H., Zhu, L., Kord-Varkaneh, H., Santos, H. O., Tinsley, G. M., & Fu, P. (2020). Effects of intermittent fasting and energy-restricted diets on lipid profile: a systematic review and meta-analysis. Nutrition, 77, 110801.
  7. Santos, H. O., & Macedo, R. C. (2018). Impact of intermittent fasting on the lipid profile: assessment associated with diet and weight loss. Clinical nutrition ESPEN, 24, 14-21.
  8. Dong, T. A., Sandesara, P. B., Dhindsa, D. S., Mehta, A., Arneson, L. C., Dollar, A. L., … & Sperling, L. S. (2020). Intermittent fasting: a heart healthy dietary pattern?. The American journal of medicine, 133(8), 901-907.
  9. Cho, Y., Hong, N., Kim, K. W., Lee, M., Lee, Y. H., Lee, Y. H., … & Lee, B. W. (2019). The effectiveness of intermittent fasting to reduce body mass index and glucose metabolism: a systematic review and meta-analysis. Journal of clinical medicine, 8(10), 1645.
  10. Nowosad, K., & Sujka, M. (2021). Effect of Various Types of Intermittent Fasting (IF) on Weight Loss and Improvement of Diabetic Parameters in Human. Current Nutrition Reports, 1-9.
  11. Barnosky, A. R., Hoddy, K. K., Unterman, T. G., & Varady, K. A. (2014). Intermittent fasting vs daily calorie restriction for type 2 diabetes prevention: a review of human findings. Translational Research, 164(4), 302-311.
  12. Varady, K. A. (2014). Intermittent fasting vs daily calorie restriction for type 2 diabetes prevention: a review of human findings. Translational Research, 164(4), 302-311.
  13. Ravussin, E., Beyl, R. A., Poggiogalle, E., Hsia, D. S., & Peterson, C. M. (2019). Early time‐restricted feeding reduces appetite and increases fat oxidation but does not affect energy expenditure in humans. Obesity, 27(8), 1244-1254.
  14. Gaeini, Z., Mirmiran, P., & Bahadoran, Z. (2021). Effects of Ramadan intermittent fasting on leptin and adiponectin: a systematic review and meta-analysis. Hormones, 1-10.
  15. Correia, J. M., Santos, I., Pezarat-Correia, P., Minderico, C., & Mendonca, G. V. (2020). Effects of intermittent fasting on specific exercise performance outcomes: A systematic review including meta-analysis. Nutrients, 12(5).
  16. Levy, E., & Chu, T. (2019). Intermittent fasting and its effects on athletic performance: a review. Current sports medicine reports, 18(7), 266-269.