CAUSES OF OBESITY IN CHILDREN AND ADOLESCENTS
The cause of obesity is complicated and there is still much to clarify, due to multiple implicating factors, such as genetic, environmental, neuroendocrine, metabolic, behaviour and lifestyle.
Environmental changes (an increase in the ingestion of calories and reduction of physical activity) are considered principal factors in the current increase in the prevalence of obesity in the world.
There are numerous external factors involved in the pathogenesis of childhood obesity. Among these, the ones that stand out are: an excess of feeding during the prenatal period and during lactation, maternal malnutrition, type of family structure (only child, adopted children, the last child in a big family, separated parents, single-parent family, mother older than 35, numerous family members) socio-economic level (lower social class in developed countries and higher class in countries heading towards development), factors related to climate, lack of exercise and easy access to food. One environmental factor that is related to the increase in obesity in our society is watching television for many hours a day.
In addition, the imbalance between the ingestion and burning of energy that facilitates the accumulation of fat seems influenced by a genetic predisposition of each individual and their lifestyle. It is estimated that 25-35% of cases of obesity occur in families in which the weight of the parents is normal; although the risk is greater if the parents are obese. The standard of body fat distribution (central and peripheral) continues with the same tendency observed in parents. Some studies have demonstrated that the weight of adopted children significantly correlates to the weight of their genetic parents.
Studies done on twin siblings also show the heredity of fat mass. There is then a genetic basis that can act on different mechanisms like the preference for different types of food, the modulation of energy consumption, the standard of fat distribution, the thermogenetic effect of food and the grade of physical activity.
However, the risk of being obese can be attributed to following similar eating habits in a genetically predisposed family.
Congenital diseases (Prader-Willi syndrome, Alstrom syndrome, Cohen Syndrome) are rare causes of obesity. Endocrine diseases (like hypothyroid, Cushing syndrome) are also not frequent causes of weight disorders.