Intermittent fasting: what you need to know

Maintaining a healthy body weight has many benefits. People who are not overweight are less prone to joint pain, the development of diabetes, cardiological and some oncological diseases. There are many ways to maintain a healthy weight. For several decades, the Mediterranean diet has been considered one of the most useful nutritional systems, which not only allows you to maintain normal weight, but also is a source of most essential nutrients for the body.

However, in recent years, another trendy diet has appeared, which many consider a panacea for obesity and the easiest way to lose weight without giving up your favorite foods. It’s about intermittent fasting. Is this system as useful as many are sure what it is and are there any contraindications to intermittent fasting? Let’s figure it out together, based not just on the rave reviews of those who have lost weight, but on real scientific facts.

What is intermittent fasting

Intermittent fasting, or fasting, is a regimen in which it is necessary to completely refuse to eat food during certain hours, and eat as usual the rest of the time.

Intermittent fasting is a pretty flexible system. Everyone can determine for himself the duration of the period for which he plans to refuse food.

There are different models of IG:

• 16: 8;
• 14: 10;
• 20: 4;
• 23: 1;
• 24: 24;
• 36: 12.

In addition, many people follow the 5:2 system – when for 2 days a week the daily calorie intake is reduced to 500 kcal, and on the other days they adhere to their traditional diet.

But still, when people talk about intermittent fasting, they most often mean the 16:8 system. It provides daily fasting for 16 hours. There is an 8-hour window for eating in the day. At the same time, there are no strict restrictions on when it should be. Some people feel comfortable skipping breakfast in favor of a hearty lunch and dinner, while others, on the contrary, refuse an evening meal. And it does not affect the result of the IG. The most important thing is to eat only during the 8-hour window.

For comparison. In the 20:4 system, only 4 hours a day are allotted for food. Such a system allows you to lose weight more quickly, but as a long-term nutritional model, this is not the best choice.

In fact, each period of time between meals can be called intermittent fasting. For example, when a person does not have time to have breakfast in the morning and the first meal after dinner falls on lunch, this is already intermittent fasting. But if the task is to get real results from IS, then such a system should become regular.

How it works

The essence of IG, regardless of the chosen model, is identical: during a period of sharp reduction in calories, the body uses stored fat for energy ^[1].

IG is nothing new. This is one of the oldest food systems. This is the way of life that ancient people led.

In terms of food intake, the human body can only be in one of two states: satiety or hunger. That is, either the body is engaged in the accumulation of energy from food (increases its energy reserves), or it burns the accumulated energy (reduces reserves). If the periods of nutrition and hunger are balanced, then body weight does not change significantly.

A modern person, as a rule, consumes more food than the body actually needs. Everything that has not been used is deposited in the “repositories” in the form of fat accumulation. That is, if a person, from the very morning until late in the evening, eats food, then the body is constantly in a full state and accumulates energy. So over time, overweight and obesity appear. Intermittent fasting helps to restore this balance. Simply put, IG allows the body to expend stored energy.

When we eat, the body uses carbohydrates as energy and stores the excess in the liver as glycogen or turns it into fat. After a meal, the body uses carbohydrates as “fuel” for several hours. The “fuel” glycogen accumulated in the liver is enough for about 8 hours, and if after this time the body is not given another portion of food, it begins to take energy from the accumulated fat.

Thus, the longer the period of fasting, the more fat will be consumed by the body. But as soon as he receives the slightest portion of carbohydrates, for example, in the form of coffee with a meager amount of sugar, the process of splitting fats will stop and the body will switch back to the mode of burning carbohydrates and accumulating glycogen, as well as fat.

That is, if the last meal was at 22:00, then the body will begin to burn fat at about 6 o’clock in the morning. If breakfast is at 8:00, then only 2 hours remain to burn fat reserves. And fasting allows you to extend this time.

What Modern Research Says

The first studies on intermittent fasting and its impact on the human body were conducted back in 2012. ^[2].

Then a group of American researchers, after lengthy observations, came to the conclusion that IG brings more benefits to the body than the usual calorie reduction. Scientists conducted their first studies on mice. In a scientific experiment, two genetically identical groups of mice took part, which were fed a diet high in fats, simple sugars, and also low in proteins (this is approximately how most modern people eat). Despite the fact that both groups of animals consumed the same food, the former had access to it for 24 hours, while the others only 8. After 18 weeks, the mice, which could eat at any time, showed signs of insulin resistance, as well as liver damage. . Representatives from the other group did not have such signs, despite the fact that the calorie intake was identical for everyone. Later, the scientists repeated the same experiment with 3 more groups of mice and got the same result each time.

During the study, experts discovered another interesting point. The shorter the food intake window, the less weight the animals gained. But even when the mice were given two “days off” per week and could eat without restriction, the mice still gained less weight than their “brothers” who had access to food for 24 hours a day.

Then the same scientists conducted another experiment. They switched mice, which had gained excess weight due to unrestricted feeding, to intermittent fasting, while the daily caloric content of the diet was not changed. Animals got rid of not only excess weight, but also insulin resistance.

Of course, more complex processes occur in the human body than in the bodies of mice, but intermittent fasting affects humans in much the same way.

Benefits of Intermittent Fasting

Based on the results of scientific research, many scientists claim that IG has a positive effect on the human body. Among the most obvious benefits is weight loss, but this is by no means the only plus of such a nutrition system. Various popular systems of detoxification and purification of the body from toxins are built on the principles of fasting, which in turn is called one of the factors that slow down the aging process.

According to research ^{[3] [4] [5] [6] [7] [8]}, observance of IG contributes to:

• faster breakdown of fat, including visceral;
• decrease in blood sugar levels and the amount of insulin produced;
• reduce the risk of developing type 2 diabetes;
• improve brain function and concentration;
• lowering blood cholesterol, including “bad”;
• the process of autophagy (cleansing from dead cells);
• the production of growth hormone (in combination with autophagy, it contributes to the renewal of the body);
• reduce the risk of inflammatory processes;
• normalization of the body’s sensitivity to leptin (the hormone responsible for the feeling of hunger);
• improvement of intestinal motility.

In addition, many people who adhere to the IG system claim that they feel more alert, respond more easily to stressful situations, and more easily concentrate on work.

Contraindications to IG

Despite the impressive list of positive properties, fasting in some cases may be contraindicated. In particular, the ban applies to people who need a diet rich in nutrients, and these are:

• children;
• pregnant and lactating women;
• persons with insufficient body weight (BMI below 18,5);
• people with eating disorders such as anorexia.

With extreme caution and only with the permission of a doctor, the principles of IG can be followed by people with diabetes, gout, liver, kidney or heart disease. Fasting is also contraindicated while taking certain medications.

It is worth considering that in some cases, side effects occur against the background of IG, for example:

• a strong feeling of hunger (as a rule, if there are too few carbohydrates in the diet);
• constipation;
• headaches (usually in the first days of IG);
• dizziness (usually if you consume very few calories during the eating window).

To avoid side effects, don’t start right away with a small eating window. If you are used to eating from early morning until late at night, you can first reduce the eating window to 12 hours, and then gradually bring it up to 8, 6 or even 4 hours a day.

Intermittent fasting is a very flexible system and everyone can choose the most comfortable model for themselves. But still, if the main goal is to get rid of excess weight, then even during the eating window, you should be more careful in choosing products, giving preference to healthy ones. In addition, no matter how healthy IG is considered, following this nutrition system, you need to listen to your body and not overdo it, because a long refusal of food can be no less dangerous than regular overeating.

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