Everything you need to know about interval fasting

Intermittent (interval) fasting is one of the rapidly developing areas in the field of personal health and fitness. The technique allows you to start the regeneration process at the cellular level and has many other proven beneficial properties.

The essence of periodic fasting

Interval fasting (English: intermittent fasting) is a special diet in which the intervals of eating and starvation alternate.

There are many different Periodic fasting schemes , in which days or weeks are divided into different (by duration) time intervals of fasting and eating.

Usually, the body quickly gets used to a new diet (in just a few days) and easily tolerates such "stressful loads". Everyone already partially adheres to this technique, because during sleep we do not take food. It remains only to prolong this period of hunger.

Home the benefits of interval fasting - starting the process autophagy , that is, the natural regeneration of the body's cells. The process of autophagy was discovered by Japanese scientist Yoshinori Osumi, for which he was awarded the Nobel Prize.

At the moment, a huge amount of research has been conducted on the effects of fasting on the body. It has been proven that it allows you to reduce body weight, improve the health of almost all body systems and increase overall life expectancy.

Basic Circuits

Currently, many periodic fasting protocols have been proposed, each of which has its own characteristics.

The founders of most of them are leading scientists, fitness experts and healthcare professionals.

The most popular and studied protocols are discussed below:

1. Method 16/8 : Starve for 16 hours every day. This is the most popular and studied scheme. According to it, you need to give up food for 16 hours, and eat in the remaining 8 hours. The scheme can be followed from 1-2 times a week to a permanent basis. The diet has more gentle variations: fasting from 10 to 14 hours a day (recommended for beginners). Fitness expert Martin Berhan came up with such a nutrition schedule.
2. Method 5:2 : fast for 2 days every week. According to this protocol, you can eat any food in the desired amounts for 5 days a week. In the remaining 2 days, limit food intake to 25% of the recommended daily calorie intake, which is about 500 calories for women, 600 calories for men. Fasting days can alternate in any order (for example, Monday and Thursday) or follow each other.
3. Fasting every other day : a day to eat, a day to starve. This diet implies that the usual amount of food is taken on the first day, and 20-25% of the recommended daily energy value (about 500-600 calories) on the second day. The scheme can be repeated an unlimited number of times. The developer of this area is Krista Varadi (health worker).
4. The Warrior's Diet : Starve during the day, eat at night. The essence of the protocol is to refuse to eat for 20 hours, and then eat any amount of food before going to bed. During fasting, small snacks are allowed (raw fruits and vegetables, hard-boiled eggs). This diet has the most contraindications and is not recommended for beginners. The founder is a former employee of the Israeli special forces, Ori Hofmekler.
5. FMD diet : there are few 5 days a month. This variant of fasting is characterized by a massive evidence base. The meaning of the method is to limit the calorie content of the diet 5 days a month. The composition of the food is subject to special correction. Day 1: daily caloric content – 54% of the recommended value (about 1090 kcal), proteins – 10%, fats – 56%, carbohydrates – 34%. From day 2 to 5: daily calorie content – 34% of the recommended value (about 725 kcal), proteins – 9%, fats – 44%, carbohydrates – 47%. The copyright belongs to employees of the University of Southern California (USA).
6. The "Eat-Stop-Eat" Method: fast for 24 hours once or twice a week. The scheme was developed by fitness expert Brad Pilon and is considered extremely difficult to perform, but this did not prevent it from becoming one of the most popular types of interval fasting. The main principle of the diet is fasting for 24 hours 1 or 2 times a week.
7. Spontaneous skipping of a meal. is the simplest and safest option for short-term fasting. You just need to skip some familiar meal, for example, breakfast or dinner.

It is important to note that in the process of fasting, according to any scheme, it is allowed to take unlimited amounts of water, tea or coffee without sugar. This is necessary to avoid dehydration of the body. Avoid dry fasting methods.

Effects on cells and hormones

During fasting, many changes occur in the body, both at the cellular and molecular levels. The work of the genetic apparatus and a number of enzymes is changing, which ensures the improvement of metabolic processes and the restructuring of the intracellular apparatus.

Changes in gene activity

American specialists proved that during fasting, the activity of kinase – mTOR decreases (due to the low intake of methionine and carbohydrates into the body).

This contributes to the launch of a special process in cells – autophagy – the processing of "intracellular debris" under the action of lysosome enzymes. As a result, the cells are rejuvenated.

Also proven that periodic fasting can prevent malignant transformation of cells of any tissue. The effect is associated with activation of SIRT1-3 gene expression.

In addition, scientists celebrate that during the temporary refusal of food, the activity of neurotrophic factors increases, the work of which is due to genetic characteristics (BDNF). As a result, the production of insulin-like growth factor-1 (IGF-1) and NF-kb, which play an important role in the development of malignant neoplasms (especially in nervous tissue) and a number of neurodystrophic pathologies (Alzheimer's disease), is inhibited.

Hormonal changes

According to foreign experts, during fasting, the level of insulin in the body significantly decreases, which makes fat deposits available for disposal in order to obtain energy. The sensitivity of peripheral tissues to insulin also increases and glucose concentration decreases, which has a positive effect on the general glycemic background.

Installed that during a diet, the concentration of growth hormone increases at least 5 times. This promotes faster utilization of adipose tissue, preservation of muscle cells, improvement of physical and mental work, increase of mineral bone density and Immune activation .

Additional "fat burning" effect provides increased production of norepinephrine under the influence of signals from the brain.

Effectiveness for weight loss

Overweight or obesity is the most common reason why people start the practice of intermittent fasting. Similar information lead British scientists.

The technique allows you to reduce the overall energy value of the diet, changes the work of hormones and the expression of a number of genes, stimulates the brain. According to research , the described mechanisms accelerate metabolism from 3.6 to 14%.

Scientific research demonstrates that such fasting can be a powerful tool for weight loss.

For example, one of the major experiments conducted in 2014, showed that if this technique is followed, body weight can decrease by 3-8% in 3-24 weeks. The indicator surpasses most of the "standard" modern diets.

There was also a decrease in waist size by 7% and a decrease in the incidence of various cardiovascular and endocrine diseases caused by obesity.

The advantage is also that interval fasting preserves muscle tissue . Conventional diets (which reduce the daily calorie content of the diet by 10-30%) cause muscle breakdown.

So, research discovered that hunger reduces the concentration of insulin-like growth factor-1 in the blood, which causes less loss of muscle tissue. To improve the safety of the musculoskeletal system, scientists recommend combining the technique with active regular physical activity (feasible training for 40-50 minutes a day at least 5 times a week).

One of the scientific papers revealed that even a banal spontaneous skipping of food (lunch) contributes to a more effective loss of body fat and muscle tissue growth.

6 more useful properties

A number of proven benefits of interval fasting in relation to the human body are considered below:

1. Prevention of type II diabetes mellitus . As already mentioned, the diet causes reduction of IGF-1 in the blood, which increases the sensitivity of peripheral tissues (muscle and fat) to insulin and more efficient utilization of glucose. It is with this pathogenetic mechanism that the development of type II diabetes mellitus and other disorders of the glycemic background (fasting hyperglycemia, impaired glucose tolerance) is associated.
2. Cardioprotective effect . Heart and vascular diseases occupy leading positions due to mortality in almost all countries. Proven that fasting reduces high blood pressure, provides correction of dyslipidemia (reduction of total cholesterol, TAG and LDL), reduces blood sugar levels and a number of markers in the blood. As a result, a number of (including fatal) diseases are prevented: coronary heart disease, myocardial infarction, ischemic or hemorrhagic stroke.
3. Prevention of brain pathologies. Contrary to modern scientific ideas, American scientists discovered that a decrease in IGF-1 concentration during fasting stimulates the growth of new nerve cells. Also, the diet allows you to prevent depressive disorders , Alzheimer's, Pick's, Parkinson's disease.
4. Cancer Protection . More and more modern scientific research shows that intermittent fasting significantly reduces the likelihood of malignant transformation of body cells. The technique also reduces toxicity and increases the effectiveness of chemotherapy for existing cancer processes.
5. Slowing down aging. As already mentioned, giving up food stimulates autophagy is the main mechanism for preventing aging. Each cell of the human body is updated, and the "construction" of new organelles with more pronounced functional activity is launched in it.
6. Increase in life expectancy. Experiments on rats demonstrated that periodic starvation can increase the lifespan of rodents by 83%. Fasting also prevents the development of the most common diseases among modern people. This, in turn, reduces the risk of early mortality.

Can women starve?

Some studies show that cyclic fasting is less beneficial for women. We wrote more about this in in a separate article .

The assumption is based on the fact that in women, fasting can lead to impaired blood glucose metabolism and provoke the development of hyperglycemia, even with increased sensitivity of peripheral tissues to insulin.

Experiments on female rats  shown that prolonged hunger can contribute to infertility, the development of male sexual characteristics (due to changes in the cyclicity of hormone secretion into the blood) and menstrual irregularities. However, these changes are reversible and are quickly leveled when the diet is stopped.

Also, as already mentioned, it is strictly forbidden to starve during pregnancy and breastfeeding, during the preparation for conception of a child.

Contraindications

This type of fasting has a certain list of contraindications, in which its use can not only negate all positive effects, but also cause significant harm to the body.

Here are the main contraindications:

1. Low body weight (BMI less than 18.5). An attempt to reduce weight in such a condition is fraught with a decrease in the functional reserves of the body, the development of atrophic changes in all organs, and a critical decrease in the body's resistance to various viral, bacterial, and fungal pathogens.
2. Pregnancy and breastfeeding. During gestation and feeding of the fetus, the body needs not only an increased intake of nutrients, but also a variety of vitamins, macro-, microelements. Fasting can significantly reduce the supply of extremely important elements to the fetus, which can lead to a violation of adequate development.
3. Infertility. Selected studies discovered that intermittent fasting can cause temporary infertility and various menstrual disorders. It is not recommended to practice the technique in the presence of pathologies of the reproductive system accompanied by infertility, as well as in preparation for conception.
4. Peptic ulcer of the stomach and duodenum, chronic gastritis. With prolonged hunger, the stomach continues to produce hydrochloric acid, which negatively affects the mucous membrane. In the presence of active inflammatory changes, fasting even for 3-6 hours provokes a deterioration in the general condition or an unforeseen exacerbation.
5. Cholelithiasis. Hunger alters bile secretion and significantly increases the risk of new gallstones.
6. Age less than 14 and over 75 years old. At a young age, the child's body needs a constant supply of nutrients, their restriction leads to a violation of the development of the musculoskeletal system and disorganization of mental activity. In the senile period, any stress load is undesirable (hunger is always stress for the body).
7. Any pathology of the thyroid gland with hyperthyroidism. An increase in T3 and T4 in the blood significantly increases the feeling of hunger and makes it impossible to practice fasting. Also, with this condition, it is possible to exacerbate chronic diseases of the digestive system.
8. Chronic cardiac (IIb-III), liver or kidney failure. The breakdown of adipose tissue increases the functional load on the liver (this can lead to an aggravation of the general condition). The same applies to the kidneys, since by-products of metabolism are excreted through these organs. With decompensation of blood circulation (CHF IIb-III), any stress can become fatal.
9. Refractory hypertension. With arterial hypertension, which does not respond to pharmacotherapy, any lifestyle change can provoke an unexpected sharp rise in blood pressure, hypertensive crises in this condition are usually complicated.

Contraindications also include:

• Active course of tuberculosis of any organ;
• Type I diabetes mellitus;
• AV blockades of II-III degree;
• Tachycytolic arrhythmias;
• Thrombophlebitis or any history of thromboembolic complications (PE);
• Arterial hypotension.

Side Effects

Fasting patterns are usually well tolerated by the human body. At first, of course, it is possible to develop a feeling of intense hunger, which disappears after a few days and does not cause noticeable discomfort.

If the calorie content of the diet is insufficient (especially when combined with regular physical activity), signs of exhaustion of the body may appear:

• General weakness;
• Vertigo;
• Flashing of "flies" in front of the eyes;
• Unsteadiness or swaying when walking;
• Increased drowsiness (especially during the day);
• Decreased mental and physical performance.

The development of any of the described symptoms does not indicate an insufficient supply of nutrients to the body and should serve as a reason to discontinue the protocol in order to correct it later. It is advisable to solve such a problem together with a doctor.

Answers to frequently asked questions

Intermittent fasting has many subtleties. To avoid mistakes, it is advisable to know the answers to some important questions:

1. Is it possible to drink water, tea, coffee during fasting? During the refusal of food, it is allowed to drink any low-calorie drinks (tea or coffee without sugar), regular or mineral water. High-calorie foods (tea with sugar) and various sweet drinks rich in dyes, preservatives and flavor enhancers (Coca-Cola) should not be abused.
2. Can I drink alcohol? This issue is considered controversial. On the one hand, alcohol causes a sharp decrease in IGF-1, which significantly increases the effectiveness of fasting. However, alcoholic beverages increase the negative effect on the mucous membrane of the stomach and duodenum, disrupt the functioning of the liver and pancreas. Therefore, it is better not to drink alcohol during fasting unless absolutely necessary.
3. Can I smoke? Nicotine activates the sympathoadrenal system, increasing the functioning of the cardiovascular system, it also increases the activity of "aggression factors" in relation to the gastric mucosa. The heart, blood vessels and digestive system suffer during fasting, but the negative effect is fully compensated. Smoking can disrupt this balance and is contraindicated in any case.
4. Is it harmful to skip breakfast? Not if full-fledged healthy food is consumed during the rest of the day. It also does not affect the general well-being.
5. Is it possible for people to starve after 50? According to official recommendations, the extreme age at which intermittent fasting can be practiced is 75 years old. Therefore, in the period from 50 to 75 years, in the absence of contraindications and good tolerability, the technique is safe.
6. How long can I keep a fasting regime? Is it possible to observe it all your life?  Short-term fasting can be practiced for a long time. The main thing is to ensure that the body receives all the necessary nutrients (proteins, fats, carbohydrates, vitamins, micro–, macronutrients).
7. Can I take supplements? Yes! During hunger, various biologically active additives (vitamins, macro- and microelements), on the contrary, are necessary. They make it possible to improve the tolerance of the diet and compensate for the possible deficiency of certain elements.
8. Is it possible to train? Regular physical exercise is the basis of a healthy lifestyle. In addition, feasible loads allow you to additionally keep the body in good shape and prevent possible loss of muscle tissue volume.
9. Is it possible to lose muscle mass? As already mentioned, research demonstrates that interval starvation does not cause loss of muscle tissue, or it is insignificant. In order to prevent this phenomenon, it is necessary to increase the level of protein intake (in the absence of kidney failure) and lead an active lifestyle.
10. Is metabolism slowing down? No, short-term fasting, on the contrary, accelerates metabolism by 4-14%.
11. Is it possible to follow the methodology for children and adolescents? The diet is recommended only for people over 14 years old. At a young age, there may be disorders of the development of the musculoskeletal system, changes in the functioning of the central nervous system.
12. Which is better: fractional nutrition or periodic starvation? Fractional nutrition is a special diet option for patients with gastroenterological profile. It does not allow you to adjust your appetite, does not cause a decrease in body weight and, often, contributes to the development of obesity. It also slows down the metabolism. Therefore, short-term fasting is more beneficial to the body.

Conclusion

1. Thus, intermittent fasting is extremely useful for humans: it reduces body weight, promotes the prevention of diseases of the cardiological, endocrinological, neurological profile, and prevents malignant cell transformation.
2. There is a slowdown in the natural aging processes and an increase in overall life expectancy.
3. There are many fasting protocols. Each differs in the duration of food withdrawal, the composition of the diet, the range of positive effects, the evidence base and tolerance. For beginners, the 16/8 scheme and its simplified versions are perfect (10/14, 12/12, 14/10).
4. Do not forget that the technique has enough contraindications, side effects may develop.
5. It is recommended to consult a doctor beforehand to make sure that the body is prepared for a diet.