Fasting: benefits and risks

Fasting is usually associated with religious fasts, the most famous of which is the Muslim month of Ramadan. Right now, billions of Muslims are taking part in this act of affirming their faith, requiring them to give up food and water during the daytime. The reason for fasting during Ramadan is spiritual beliefs, but many people resort to fasting in order to lose weight and improve their health. Is it advisable?

The results of numerous studies conducted in recent years indicate that periodic fasting has a positive effect on many health indicators, including causes a decrease in body weight, blood pressure and cholesterol levels in the blood. This has made periodic fasting one of the most popular trends in dietetics.

One of the most well-known diets based on periodic fasting is the so-called "5:2 diet". If you follow this diet, you can consume a normal amount of calories for 5 days a week, and during the remaining two days, you can reduce your calorie intake to 25% of the recommended, that is, up to 500 calories for women and 600 calories for men.

The developer of this diet, Dr. Michael Mosley, claims that this approach allows not only to lose excess weight, but also has a positive impact on overall health. According to the results of scientific research, periodic fasting not only improves blood pressure and cholesterol levels in the blood, but also normalizes tissue sensitivity to insulin. So, drinking only water for one day a week reduces the risk of developing diabetes in people who are at risk for this disease. 

Scientists from the University of Southern California, working under the guidance of Dr. Walter Longo, have also demonstrated that longer periods of fasting, lasting 2-4 days, are even able to "reset" the immune system by eliminating old and forming new immune cells. It is believed that this process can protect the body from damage caused by factors such as aging and chemotherapy.

However, what mechanisms underlie the positive effects of fasting?

Since during fasting the body cannot receive energy from food, it consumes glucose stored in the form of glycogen in the liver and muscle tissue. This process starts about 8 hours after the last meal. After the glucose reserves run out, the body begins to extract energy from fat deposits, which can lead to a decrease in body weight.

In parallel, the process of detoxification of the body takes place, since any toxins deposited in the adipose tissue are dissolved and excreted from the body. In addition, after several days of fasting, the levels of endorphins – the so–called "happiness hormones" - significantly increase in the blood, which can have a positive effect on a person's state of mind.

The above-mentioned positive effect of fasting on the immune system is due to the fact that in conditions of starvation the body tries to save energy, including by processing old and damaged immune cells. Experiments on mice have shown that repeated 2-4-day fasting cycles for 6 months ensure the replacement of old and damaged immune cells with new ones. 

Moreover, researchers have demonstrated that 3-day fasting before the start of a cycle of chemotherapy protects the immune system from the harmful effects of chemotherapy drugs, which can be explained by the renewal of the immune cell population.

However, some researchers and health experts warn that periodic fasting has its negative sides, and some people are not recommended to resort to such diets at all.

According to the statement of the UK Public Health Service, periodic fasting is associated with many potential health risks.

Starving people often suffer from dehydration (dehydration), which is mainly due to the lack of fluid intake from food. Therefore, during fasting, it is recommended to ensure the intake of sufficient water into the body.

If a person is used to eating breakfast, lunch, dinner and snacking between main meals, periodic fasting can be a very difficult task for him. In such cases, fasting can lead to increased stress levels and sleep disorders. Dehydration, hunger and lack of sleep during periods of fasting can cause headaches.

The absence of food reduces the production of digestive juices, but appetizing smells and thoughts about food can trigger the production of gastric juice, an excess of which in an empty stomach can lead to heartburn.

Some nutritionists believe that periodic fasting does not provide weight loss in the long term. They claim that fasting leads to a rapid decrease in body weight due to the excretion of fluid. At the same time, the resumption of a normal diet quickly leads to the return of the dropped kilograms.

There is also an opinion that due to periodic fasting, people may neglect recommendations for a healthy diet, such as eating large amounts of vegetables and fruits. Many experts also fear that it increases the risk of developing eating disorders or compulsive overeating. Therefore, people who are prone to developing such disorders should refrain from periodic fasting.

Such diets are contraindicated for people with low body weight under the age of 18, pregnant women, patients with type 1 diabetes mellitus and undergoing a recovery period after surgical interventions.

At the same time, Dr. Longo believes that the positive effects of fasting can be achieved in another way. The results of a recent study conducted by his group indicate that the so-called "fast-mimicking diet" allows you to simulate the effects of fasting without depriving a person of food and associated side effects.

Experiments on mice have shown that such a diet triggers the process of updating the immune system and increases life expectancy. Moreover, when conducting a preliminary clinical study, following such a diet for 5 days a month for 3 months reduces the severity of a number of biomarkers associated with aging, cardiovascular diseases, diabetes mellitus and cancer.

The developers of the diet note that a large randomized clinical trial is necessary to confirm its effectiveness. At the same time, they hope that very soon doctors will be able to officially prescribe it to their patients.

In any case, to date, all people interested in the positive effects of fasting should consult a specialist before starting such interventions.

Evgeniya Ryabtseva

Portal "Eternal youth" http://vechnayamolodost.ru
based on Medical News Today: Fasting: what are the health benefits and risks?30.06.2015