Reasons and mechanism of development of obesity
Excessive adjournment of fat at the person (obesity) - difficult process. According to modern representations, it can begin under different conditions: the increased receipt of food, insufficient use (mobilization) of reserve fat as power source; excess formation of fat from carbohydrates.
At the healthy person balance of the consumed and spent calories very precisely is regulated: at change of energy costs in the corresponding degree appetite and consumption of food change. It provides quite steady constancy of weight under the changing environment conditions. Corpulent people in this perfect system of metabolism have deviations therefore violations of dynamic balance between amount of the energy arriving with food and organism energy expenditure appear, and arrival prevails over expense.
Excessive adjournment of fat in fatty tissue is connected, of course, first of all with excess consumption of food and first of all carbohydrates which, as we know, in organism easily turn into fats.
Receipt of food in organism at continuously changing expenditure of energy is regulated by the food center which represents, for I. P. Pavlov, functional merging of the nervous centers located in bark, subcortex and trunk part of brain. One of forms of manifestation of function of this center is appetite, feeling of hunger.
Activity of the food center is subject to the most various influences. The big part is assigned to influence of nervous impulses (signals) arriving from different receptor fields (olfactory, visual, flavoring analyzers, receptors of digestive tract) here. So, dominance of irritable process in the food center can be caused by initiation of the flavoring nervous terminations in oral cavity or stomach receptors, for example, at frequent testing of food, the use of sharp snack, spices, delicious dishes. Quite often it is observed at the persons working at catering establishments (workers of dining rooms, restaurants).
Processes of metabolism exert impact on activity of the food center. So, all states which lead though to small, but permanent lowering of content of sugar in blood can be followed by dominance in the food center of irritable process and, therefore, overeating and development of obesity.
Tendency to obesity appears at some persons upon transition from physical work to slow-moving way of life. At the same time power expenditure at them considerably decrease, and the habit to eat the increased quantity of food remains. It leads to overeating and obesity.
Quite often completeness develops at senior citizens that to a certain extent it is also possible to explain with discrepancy between the remained level of former excitability of the food center and smaller power expenses. It is known that by 25 years physical development of the person comes to an end. The most intensive exchange processes are characteristic of this period of life, maximum is also the main exchange. Each next decade the size of the main exchange decreases by 2-7,5 percent while food habits, appetite, quantity of the eaten food remain the same. The relative overeating and increase in weight is caused.
It is necessary to add to it that very often after 25-30 many people cease to go in for physical culture and sport owing to what their muscular activity and energy costs go down. At people with normal regulation similar deviations in way of life lead to the corresponding loss of appetite and the power balance is established at the new, more lowered level. At imperfection of this regulation of adequate correction of appetite and exchange does not come, and reception of former quantity of food inevitably leads to increase of weight.
Development of obesity can be connected with long stay on bed rest at different diseases. Decrease in energy expenditure at these patients at normal, and at some - and at excess food often leads to fast increase of weight and developing of obesity.
The special role in regulation of appetite and exchange processes belongs to subcrustal formations and the centers of hypothalamus. Processes of digestion and absorption of fats, accumulation of fats in fatty depots, transition of carbohydrates to fats are constantly regulated by these departments of brain.
At defeats of hypothalamic area appetite is broken, there are exchange diseases. However at usual obesity of change in these departments of brain have character functional, but not rough, organic.
In development of obesity, in addition to the excessive volume of food, also violation of its mode matters. For example, in connection with professional or household features the most plentiful meal is postponed to later hours of the second half of day when physical activity of the person usually decreases. Besides, long breaks in food lead to excessive arousing appetite, and in this case the person eats quickly, with greed and owing to overdue approach of sense of fulness in most cases overeats.
Important role in origins of obesity is played by violations from endocrine glands. Often these violations are expressed unsharply, it is possible to find them only at careful research.
Endocrine glands synthesize and emit hormones which differently influence fatty exchange. One of them promote splitting and mobilization of fat (lipolysis) from places of adjournment, others, on the contrary, increase its education (lipogenesis). The most intensive impact on processes of lipolysis is exerted by growth hormone produced by front share of hypophysis and also hormones of thyroid gland. At long starvation at the person increases products and allocation in growth hormone blood that leads to splitting of fat and receipt in fabric as power material of fatty acids. Increase of function of thyroid gland usually is followed by falling of body weight, and its decrease causes strengthening of fatty deposits.
The important place in regulation of exchange of fat belongs to pancreas hormone - insulin. Excess introduction of food; especially rich with carbohydrates, causes the increased release of this hormone pancreas beta cells. As a result absorption by fatty tissue of glucose and synthesis from it of fat amplifies, exit of fatty acids from fatty tissue slows down, oppressed lipolysis, formation of glycogen is stimulated in liver, sugar level in blood goes down that, in turn, can cause strengthening of activity of the food center and increase of appetite.
From other hormonal factors influencing fatty exchange it is necessary to mention hormones of bark of adrenal glands. Obesity is also promoted by lowering and the termination of function of gonads.
Deviations as endocrine glands do not play the leading role in emergence of simple forms of obesity, but in combination with other contributing factors they in most cases lead to development of this disease.
Influence of hereditary predisposition is established approximately at half of patients with obesity. Especially accurately its role is traced at supervision over uniovular twins. It has turned out that if at one of them obesity has developed, then at another it also appears, and even if these twins lived and were brought up in different conditions. However it is not necessary to revaluate value of role of heredity in development of obesity as it can be caused by the general external reasons connected with improper feeding in family, the habit to overeating developed already in childhood. As confirmation to it can serve the researches showing that from 100 children growing at corpulent parents 74 become corpulent too. If these children are raised by people of normal build, then obesity arises only at 7 children.
The condition of fabrics, in particular fatty matters in development of obesity also. In it enzymes (lipases) participating both in fat mobilization, and in its adjournment are produced. Number of researchers including at us in the country, have found at corpulent decrease of the activity of zhiromobilizuyushchy lipase in comparison with healthy.
Thus, exceeding of normal weight at obesity arises owing to excess food (overeating), reduction of expenditure of fat from fatty depots on energy needs of organism and increase of its education, mainly at the expense of carbohydrates.
All these adverse changes in organism - consequence of violation of processes of exchange: nervous regulation changes, there are shifts in functional bonds of endocrine glands, the condition of fatty tissue is broken. However in one cases the increased appetite and overeating, in others - violations is put from endocrine glands, in the third in the forefront - disorder of function of nervous system. Dominance of these or those factors also defines clinical form of obesity.