Author: Silvia Marinova, PhD student in the Genomic Stability Laboratory at BAS

Fasting is becoming more and more popular among different groups of people – from active sports to obese people. The reason is that fasting, also known as intermittent fasting, has noticeable benefits both on our appearance and on our health. Its impact on diseases such as diabetes, dementia and cardiovascular disease is the subject of increased scientific interest and research.

We could call intermittent fasting a diet, but it rather represents a long-term way of eating. It alternates phases of fasting with drastically reduced or completely limited calorie intake with periods of normal nutrition. Or simply put , it does not change what we eat, but when we eat it.

It is a well-known fact that balanced nutrition affects our health and could in some cases delay or stop the onset of chronic diseases.  In addition, it has been shown that changing diet by overall reducing calorie intake [ref. 1] or with the introduction of periodic fasting intervals [ref. 2], it has a beneficial health effect.

How science explains fasting

As already mentioned, fasting is an alternation of periods of fasting with "windows" of eating which takes place within about 12 hours, and then it is forced to switch to fat depots as an alternative source of energy. In parallel, blood sugar levels are regulated, intracellular recovery processes are stimulated and the use of available energy is optimized. In addition, intermittent fasting is thought to increase insulin sensitivity, regulate blood pressure and reduce the impact of free radicals [ref. 4].  There are already several studies that show the beneficial effect of fasting on the restoration and maintenance of the balance of the intestinal microflora [ref. 5], which is fundamentalto our immunity, digestion and hence overall well-being.

What varieties of fasting exist

We could distinguish in general 3 varieties [ref. 6] which are based on the principle of fasting:

  • Daily fasting - eating in fixed time "windows" from 4 to 12 hours daily;
  • One-day periodic fasting or intake of a minimum amount of food;
  • Fasting-mimicking diets aimedat bringing the body to a fasting-like state by reducing caloric intake.

Daily fasting

In the type of fasting "Daily fasting" we need to eat only within a certain time range within the day. This range varies from 4 to 12 hours and does not include limiting the total amount of food taken. However, clinical studies have shown that it matters in which part of the day we eat, wether the meal is consumed in the late afternoon and evening [ref. 8].

One-day fasting

In the type"One-day fasting" take turns longer periods of strong or wholly limited nutrient intake with those of normal nutrition. These range from 24-hour intervals to several days sometimes. For example, one day of the week we can only drink water and not consume solid food. The benefits of this type of fasting have also been extensively studied and the results show increased life expectancy in model organisms, improved insulin sensitivity, better response to chemotherapy [ref. 9] in cancer patients, increased fat burning, etc.

Fasting-mimicking diets

Fastingis difficult to apply to most people, despite its many benefits, and often leads to quitting after a certain period of time.

What foods can we consume if we practice intermittent fasting

Quality, varied and well-chosen food is undoubtedly key to health and good shape. The fasting regime is no exception, and when we wonder what foods to consume, the answer again lies in a balanced diet, providing our organism with all the necessary macro- and micronutrients. This includes consumption of enough fruits and vegetables, seeds and nuts, meat and dairy products.

Is a fasting diet suitable for weight loss

Very often fasting leads to a decrease in body weight, as it stimulates fat burning. Combined with an active lifestyle and a balanced diet, it could lead to fast and effective results. However, it should be noted that compared to other diets, periodic fasting does not necessarily have a higher success rate, and the end result is individual. However, some people find it easier to follow than strict and overly restrictive diets. If we aim to lose weight but cannot resist constant restrictions, then fasting may be a good alternative that deserves attention.

Is fasting suitable for everyone?

The short answer to this question is no. Consultation with a doctor is mandatory before switching to this type of regimen. Whether it is suitable for us depends on our metabolism, what we aim to achieve and whether we suffer from certain conditions. Periodic fasting is not advisable for all people, and it is important to keep in mind that it can even be dangerous. For example, it is not desirable to practice by:

  • people with chronically low blood pressure;
  • people suffering from diabetes;
  • people with stomach problems such as ulcers and gastritis, etc.

In conclusion, we will say that fasting has many health benefits, which are the subject of a highly growing field in science. However, it should be practiced moderately, according to individual needs and under the supervision of a specialist.



  1. Caloric restriction. Mol Aspects Med. 2011
  2. Meal frequency and timing in health and disease. Proceedings of the National Academy of Sciences of the United States of America
  3. Genetic variation in the murine lifespan response to dietary restriction: from life extension to life shortening. Aging cell. 2010
  4. Early Time-Restricted Feeding Improves Insulin Sensitivity, Blood Pressure, and Oxidative Stress Even without Weight Loss in Men with Prediabetes. Cell metabolism. 2018
  5. Restructuring of the Gut Microbiome by Intermittent Fasting Prevents Retinopathy and Prolongs Survival in db/db Mice. Diabetes 2018
  6. A time to fast. Science. 2018
  7. Timing of food intake and obesity: a novel association. Physiology & behavior. 2015
  8. Impact of reduced meal frequency without caloric restriction on glucose regulation in healthy, normal-weight middle-aged men and women. Metabolism: clinical and experimental. 2008
  9. Fasting Cycles Retard Growth of Tumors and Sensitize a Range of Cancer Cell Types to Chemotherapy. Science Translational Medicine. 2012


The author:

👩 🔬 Silvia Marinova has a BSc in Molecular biology (Sofia University, Bulgaria), and a MSc in structural biology (Grenoble, France). She is currently a doctoral student at the Laboratory of Genomic Stability at IMB, BAS. Her research interests are in the field of DNA repair, microscopy and biophysics. She loves photography, painting and sports.