About metabolism in general and weight loss in particular

Telegraph "Around the World":
Took, ate and lost weight
Sergey Avilov, Natalia Alexandrova

"Fat burners" will effectively help you get rid of excess weight for a whole week and acquire a lot of new worries for life.It is especially difficult to resist gastronomic temptations during the holidays and not gain extra weight.

However, if you believe the media, it is enough to speed up your metabolism a little, and the arrows of the scales, pleasing the eye, will crawl in the opposite direction.

The scientific term "metabolism" is becoming increasingly popular among non-specialists. Increasingly, popular articles – advertising and not only – write about the acceleration, increase and improvement of metabolism, about the effective elimination of metabolic toxins. Well, after the protracted holidays, many are occupied with only one question, "metabolic": how to lose weight?

The term "metabolism" comes from the Greek word μεταβολή, which means "exchange", "destruction". Today, "metabolism" is understood as a set of chemical reactions that occur in living organisms and are necessary to maintain life.

Metabolism includes two mandatory components: catabolism – reactions in which organic substances are destroyed with the release of energy, and anabolism – reactions of synthesis of biological molecules and structures in which energy is consumed.

In addition, pharmacologists and toxicologists use the term "metabolism" to refer to the biochemical transformations of foreign substances (for example, drugs, poisons) in a living organism. Since such substances are not synthesized in the human body, but only destroyed, their metabolism is identical to catabolism. In living organisms, chemical reactions proceed many times faster than the same reactions "in vitro", thanks to enzymes – complex protein molecules, each of which accelerates only one or several similar reactions.

A hundred or a hundred and fifty years ago, scientists studied individual reactions or sequences of several reactions. Such studies were very important for the formation of the foundations of biochemistry. However, against the background of thousands of interconnected biochemical transformations, the description of individual reactions can be compared with the famous parable of blind sages who "studied" an elephant by touch. One took hold of his leg and decided that it was a pole, another rested on his side and said that it was a wall, the third felt for the tail and concluded that there was a snake in front of him.

In recent decades, so much biochemical information has accumulated that a mosaic of individual facts has finally begun to form a general (though not very clear) picture of metabolism. The situation is repeatedly complicated by the fact that metabolism is not a "screenshot", but a dynamic system of many interrelated processes. A new discipline, systems biology, is trying to model a holistic dynamic picture of metabolism with the help of computers. Such models have been created for some bacteria and yeasts whose genomes have been studied lengthwise and across.

The first comprehensive model of human metabolism, developed by a group of scientists led by Professor Bernhard O. Palsson from the University of California at San Diego (University of California), was published in 2007 in the Proceedings of the National Academy of Sciences of the USA (Proceedings of the National Academy of Sciences of the USA). The model includes about three thousand three hundred individual biochemical reactions, information about which the developers "dug up" from one and a half thousand scientific publications. The authors expect that complex models of human metabolism will make it possible to predict how a change in one metabolic reaction (for example, under the influence of medication) will affect other reactions and the state of the body as a whole.

Effective global models of metabolism can radically change biochemical and pharmacological research, partially replace time-consuming experiments "blindly". Global (and current) models of metabolism for biology are to some extent similar to the classical laws of mechanics for engineering, which allow engineers to calculate the properties of machines and buildings in advance.

Speed up to lose weightProgress in fundamental biochemistry is reflected in our everyday life.

One of the fashionable advertised principles of weight loss is "acceleration" ("increase", "improvement") metabolism. It is believed that if the metabolism is "accelerated", a person will lose weight. To "speed up metabolism", for example, coffee or preparations from plants that contain substances similar to caffeine, such as guarana, are recommended.

However, in reality, "acceleration" does not guarantee weight loss at all. Small animals have a much faster metabolism than humans, but this does not prevent them from accumulating large reserves of fat for the winter. Remember at least the marmots. It's all about the ratio of the rates of receipt and expenditure of "energy carriers". The law of conservation of energy also applies to living organisms: the energy received with nutrients must be spent on physical work, growth, and maintenance of vital functions. The remainder of the received energy is stored in adipose tissue.

It is correct to talk about the rate not of metabolism, but of catabolism – that is, metabolic processes in which organic molecules "burn up". It is the rate of catabolism that is evaluated experimentally (by the release of heat and carbon dioxide and by oxygen consumption), and it reflects the speed of destruction of fat reserves. And it is very easy to accelerate catabolism – with the help of any physical activity.

How to kill your appetite (and at the same time yourself)?One of the radical solutions to the problem of overeating, which pharmacology has "presented" to mankind, is substances that suppress appetite.

The most famous drugs from this group are amphetamines. They really reduce appetite, stimulate catabolic reactions (in which calories are burned), increase tone, serve as effective doping, so they are used illegally by athletes and legally by the military.

As a result, the amphetamine user successfully loses weight. But in addition to these "positive" effects, amphetamines cause tachycardia, increase blood pressure, lead to potentially fatal damage to heart valves, increase the risk of a heart attack, and most importantly – lead to the formation of drug addiction. Therefore, the use of amphetamines to suppress appetite has long been banned in the civilized world.

Drug manufacturers have found that a combination of caffeine, ephedrine (a central nervous system stimulant derived from certain types of ephedra) and phenyl-propanolamine (a synthetic stimulant similar to amphetamines) has a powerful "amphetamine" effect. When the severe side effects of this "triple" diet pill were discovered, this combination was also banned by the US Food and Drug Administration (FDA). The issue of the safety of "pure" ephedrine remains controversial. The department banned its use for weight loss, but the court overturned this decision. The public tends to consider natural medicines harmless, although the "green pharmacy" supplies humanity, in addition to useful things, also cocaine, opium, cannabis, narcotic mushrooms.

In 2007, the US Federal Trade Commission (FTC) filed lawsuits against four manufacturers of dietary supplements for weight loss – Xenadrine EFX, CortiSlim, One-A-Day WeightSmart and TrimSpa – with accusations of deceiving consumers who were promised improved metabolism and weight loss without effort.

Pharmaceutical companies are intensively developing new, less dangerous drugs to suppress appetite. No wonder: the potential market for anti-obesity drugs in the US alone is estimated at $61 billion. One of the world leaders in the pharmaceutical industry, Merck, is completing trials of a new drug Taranabant, which acts on the same receptors of the central nervous system as the active components of marijuana, but causes the opposite effects: marijuana leads to an increase in appetite and euphoria, and Taranabant, on the contrary, reduces appetite and leads, as it turned out, to a state of anxiety and depression, which was observed in 30% of the subjects in a recent study, the results of which are published in the journal Cell Metabolism.

Taste castrationUntil recently, for those who cannot deny themselves sweets, there were only sugar substitutes like saccharin.

The radical solution is to make the sweet taste receptors on the tongue insensitive so as not to enjoy sweet foods, that is, to turn into a kind of "gastronomic eunuch". This effect can be achieved with the help of a local anesthetic benzocaine. Components from the Gymnema sylvestris plant also reduce sensitivity to sweet and bitter. Scientists have not yet figured out whether "taste castration" is accompanied by side biochemical effects, but it is more than likely that such a change in the perception of the surrounding world will affect a person's mood.

Orlistat (Orlistat), which is sold under various commercial names, has become a fundamentally new solution to the problem of obesity, as well as the answer to dangerous drugs like amphetamines. This substance interferes with the work of enzymes that break down the most high–calorie components of food in the digestive tract - fats. Non-split fats cannot be absorbed, so they leave the intestine naturally unchanged. Orlistat, in principle, cannot cause serious side effects: it acts in the intestine without penetrating not only into cells, but even into the blood, and therefore does not come into contact with any vital structures of the body. Such a side effect as a "fat" stool is not dangerous for health. However, orlistat is not a panacea for obesity: firstly, it does not "turn off" the breakdown of fats by 100%, and secondly, it does not affect the intake of calories with carbohydrates in any way. In addition, some vitamins (A, D, E, K) are absorbed in the intestine only if they are dissolved in fats, so prolonged regular use of orlistat can lead to a shortage of these vitamins in the body.

How Libra and hunger strikes deceive usA short–term hunger strike or a diet with clearly insufficient calories is the most common way to lose weight, which corresponds to the psychology of most of us: "I start a new life on Monday."

But the body is more complicated than a car with a motor and a gas tank. If there is a lack of supply of "fuel" from the outside, first of all, reserves are mobilized not from adipose tissue, but the polysaccharide glycogen contained in the liver. Then, along with fats, proteins begin to "burn", primarily muscle tissue.

There are two pitfalls here: firstly, it is better to have more muscles for a "good" figure; secondly, muscle tissue, unlike fat, is very metabolically active: even without performing physical work, muscle cells "eat" much more calories than fat. By reducing the mass of muscle tissue, a person automatically reduces the actual needs of the body in calories at rest, and the habit of eating in accordance with previous needs remains after a week of a "hungry" diet. Another catch follows from the difference in the density of muscle and adipose tissue. A cubic centimeter of muscle weighs noticeably more than a cubic centimeter of fat. Therefore, firstly, the reduction of muscles during fasting looks impressive on the scales, although there is nothing good about it. And secondly, the reduction of adipose tissue and parallel muscle growth (the usual result of physical exercise) can lead to weight gain and disappointment ("exercise does not help me get rid of excess weight!"), while a person seems to forget that he is trying to get rid not so much of excess weight as of excess volume.

The expression "to eat vodka", which is relevant for the period of stormy holidays, can also be understood literally: alcohol is perfectly included in the chain of chemical reactions that provide the human body with energy. Moreover, the calories contained in the simple C2H5H molecule are released even faster than the calories of the glucose molecule – the fastest of conventional energy sources. Therefore, those who count the calories they have eaten should also remember about the "drunk" calories: a glass of vodka can compete with a piece of cake in terms of calories.

But what if during the holiday week you don't want to understand all this biochemistry of metabolic reactions? Oddly enough, simple principles of healthy eating were formulated in the country of gourmets – in France. The food advertising has a mandatory inscription: "Do not eat too much sweet, fatty and salty."

Portal "Eternal youth" www.vechnayamolodost.ru12.01.2009