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While the pointlessness and danger of hard restrictions and mono diets are obvious to many, then “scientifically based” diets are often tempting. Everyone has learned that extreme restrictions can lead to a decrease in metabolism - the more attractive it seems to be ways to "speed up" the metabolism by switching to certain foods, taking supplements, or simply eating small meals, but often. Do these methods work? Is it possible to force the body to burn more without changing physical activity? We asked these questions to an expert.
Our body works like a laboratory in which processes of decay, destruction - catabolic reactions, and processes of synthesis, construction, accumulation - anabolic reactions take place. They are influenced by catabolic and anabolic hormones, are in dynamic equilibrium and together constitute metabolism - metabolism. To put it simply, metabolism is a series of chemical transformations in each cell, through which the food we eat is converted into energy.
That part of the energy we have received, which is spent on the work of internal organs and systems, refers to the main exchange: this is the largest expenditure item - 50–70%. Energy is needed for the brain to think, the liver to detoxify poisons, the kidneys to filter urine. It turns out that we spend most of our energy without doing anything specifically for this. The main exchange takes place autonomously - independently of our will and consciousness.
We also spend energy on digesting and absorbing food - this is called the thermal effect of food, it accounts for about 10% of the total amount of energy received. Energy expenditure depends on the composition of the food eaten: the least calories are spent on assimilating fats, most of all on protein foods. The third component of the energy budget is physical activity. This is not only a sport, but, for example, maintaining a posture - absolutely everything we do using muscles. This is the most variable indicator - 10-30%, and even more among athletes and people engaged in hard physical labor.
At the same time, the basic metabolism of different people is not the same: if you collect a dozen people who live on 2000 kcal per day, then their basic metabolism can be from 1000 to 1400 kcal. This (or even greater) gap depends on various factors, including the activity of the thyroid hormone thyroxine, which regulates basal metabolism, and also on the surface area of the body (the greater the height and weight, the more energy is needed) and the ratio of muscle and adipose tissue in the body. The metabolically active tissues - muscles - need more energy. Women have a lower basal metabolic rate than men, and this cannot be explained by a higher percentage of fat alone; in the second (luteal) phase of the menstrual cycle, the basal metabolism is usually more active.
In addition to thyroxine, there are other molecules that affect basal metabolism: in particular, stress hormones make us use energy more actively. With age, the basal metabolic rate slows down by several percent every ten years - in part, this is due to the fact that a person becomes less mobile and loses muscle tissue. When there is a lack of calories during the diet, the body adapts to the lack of energy, also reducing the basal metabolic rate.
"Fat-burning" additives do not work: it is impossible to enter into the body a substance that is capable of breaking down fat molecules in adipose tissue and removing them
When they talk about speeding up the metabolism, it is usually suggested to do it either with the help of certain foods, or by changing eating habits - for example, switching to fractional meals. The idea of the latter is that a large number of meals "accelerates" the metabolism, since more energy is spent on its digestion and absorption - the same thermal effect. But in fact, there is no difference how much energy is spent on the thermal effect with different numbers of meals, if the total intake is the same. It is possible to increase the thermal effect by consuming more calories, but is it necessary?
Some foods - like chili peppers and coffee - can slightly increase metabolism (and the mechanisms of their effect on fat oxidation and thermogenesis are clear), but their effect is so slight and short-lived that it will not affect body weight or volume in any way. Advertisements for “metabolic-boosting” foods and supplements are based on questionable, poorly conducted, and paid for by the dietary supplement manufacturer. Numerous supplements that are positioned as "burning fat" in reality simply cannot work: it is impossible to introduce into the body a substance that is capable of breaking down fat molecules in adipose tissue and removing them. In addition, such supplements have undesirable effects on the liver - and some unlucky people losing weight in the United States took them to the transplant department. Ephedrine supplements are generally banned by the US FDA: according to a 2003 meta-analysis, they have psychoactive effects and adversely affect various systems, including the cardiovascular system.
Dietary supplements have not been tested for safety in the same way as medicines. They are not able to speed up anything (except for spending money), but they can additionally contain strong laxatives and diuretics, as well as prescription drugs for the treatment of obesity, which are prescribed according to strict indications and are taken under the supervision of a doctor. These components may not be listed at all on the labels.
The only way to gradually increase basal metabolism is to increase the volume of metabolically active tissues. More energy is spent on servicing the muscles, so its consumption will increase slightly. But there are no magic, quick and at the same time safe means to increase metabolism. As with everything that relates to the human body, the main principle should be "do no harm" - that is, do not starve, do not try on yourself severe food restrictions and "fast" diets. Extreme diets force the body to turn on the economy mode in order to make better use of the incoming food. Basal metabolism slows down, the synthesis of signaling molecules that control feelings of hunger and satiety changes.
With weight loss, a slight decrease in basal metabolic rate is logical, because you need to maintain the vital activity of a smaller number of tissues (although adipose tissue accounts for a little, 3-4% of the basal metabolic energy) - but with extreme diets this decrease exceeds expected. This leads to an interesting phenomenon: the body resists weight loss with all its might, but easily regains it. This is why there are no simple, easy and quick fixes in evidence-based nutrition.