Adipose tissue is the main deposit of triglycerides in mammals, including humans. It is made up of a set of numerous cells, called adipocytes, responsible for the synthesis of triglycerides and their release in the form of glycerol plus fatty acids. The orientation of the adipocyte towards one or the other metabolic pathway depends above all on the nutritional state of the organism.
In a 70 kg individual, the amount of fat accumulated in the adipose tissue is 11-15 kg, a sufficient caloric reserve for about two months of life.
Below the skin the adipocytes group together to form a more or less thick layer, commonly called subcutaneous adipose tissue or hypodermis.
The thickness and distribution of these fatty deposits depends on several factors, some of which are very obvious. For example, in some areas of the body the adipose panniculi are reduced (hands, feet, forearm), especially when compared with those present in other regions (abdomen, hips, buttocks).
The thickness and distribution of the subcutaneous adipose tissue is different in the two sexes. In women, for example, the fat mass is generally concentrated in the hips, buttocks, thighs and abdomen below the navel (gynoid obesity). In fact, nature wisely wanted the lipid stocks to be distributed in areas essential to carry the pregnancy to term, even in conditions of famine.
In men, an android type distribution prevails (fat mass concentrated in the face, neck, shoulders and especially in the abdomen above the navel). This latter condition is more dangerous than the previous one, since an excess of androgenic adipose tissue is associated with higher levels of blood sugar, triglycerides and blood pressure.
The extent of adipose masses also depends on the state of nutrition: it increases in the case of excessive caloric intake (obesity) and decreases in the presence of chronic nutritional deficiencies. Finally, in wellness societies, adipose tissue is generally higher in the elderly than in adolescents and young adults.
Many people believe that once fat has accumulated in certain areas of the body it is impossible to remove it. In reality, the triglycerides of the adipose tissue are not stationary, but are continuously mobilized and redeposited, renewing themselves every 10-15 days.
Classic functions of adipose tissue
Energy reserve
Impact protection and mechanical support to various organs
Body figure modeling
Thermal insulation (white adipose tissue); increase in body temperature and disposal of excess food in the form of heat (brown adipose tissue).
For further information: functions of fats; adipokines; white and brown adipose tissue (adipose tissue is no longer considered simply an inert deposit, but a real endocrine organ).
Increase in adipose tissue
The increase in fat masses can occur in two ways:
for hyperplasia: increase in the number of adipocytes
for hypertrophy: increase in the lipid content of each adipocyte
Until a few years ago it was believed that adipocyte hyperplasia occurs only in infancy. Today we know that this phenomenon can also manifest itself in adults, especially when one passes from moderate overweight to obesity. The confirmation of this phenomenon, partly intuitive, was given by the discovery of preadipocytes, undifferentiated cells immersed in the tissue. adipose of adults.These cells retain the ability to divide and, if stimulated and activated, to originate new adipocytes. Once formed, these new fat cells will remain so until the death of the individual, they can therefore increase or decrease in volume but not in number.
According to the lipostatic theory, which sees the reduction of the lipid content of adipocytes as the main stimulating factor for appetite, a large number of empty fat cells would be responsible for the attacks of uncontrolled hunger, which very often nullify the slimming diets proposed to obese people.
It is therefore important to prevent an excessive increase in adipose tissue and in the number of adipocytes, especially in children, in whom this phenomenon would most likely condemn them to remain obese for the rest of their lives.
In a normal weight subject the number of fat cells is about 25-30 billion, in obese subjects this value rises on average between 40 and 100 billion.
CONTINUE: white and brown adipose tissue "
