Causes of Childhood Obesity

Causes

The causes of childhood obesity can be broadly classified into two types: simple obesity and symptomatic obesity.

1. Simple Obesity

In Paleolithic societies, physical activity was essential for obtaining food, and because finding and acquiring food was not guaranteed, there were likely times of abundance and times of scarcity when hunting failed or food could not be found. During periods of abundance, there was no problem, but during times of scarcity when hunting failed and food could not be obtained, people with “thrifty genes” that promoted energy storage and replenishment would have had a survival advantage over those without such genes. However, the “thrifty genes” that evolved to be advantageous for survival in Paleolithic times are said to contribute to obesity in modern times. This is because people can easily obtain food at any time through the domestication of animals and cultivation of plants, physical activity has decreased as a result, and the shift to indoor living due to the modernization of civilization has made it difficult to adapt properly. As a result, excess energy continues to be stored as fat, leading to obesity. Therefore, obesity can be said to arise from both genetic and environmental factors.

1. Genetic Factors

There have been many studies to prove genetic factors, but there is still much controversy. However, obesity is said to occur intensively in certain families. Looking at the relationship with parents, when both parents are obese, 80% of children become obese; when only the mother is obese, 60% become obese; and when only the father is obese, 40% become obese. In addition, even under the same environment, the concordance rate of body mass index (BMI) is 32% in dizygotic twins but much higher at 74% in monozygotic twins. In the case of adopted children, BMI is said to be more closely related to the biological parents’ BMI than to that of the adoptive parents. However, obesity is not a simple matter that follows Mendel’s laws; it results from the interaction of multiple genes with one another, as well as habits and the environment.

2. Environmental Factors

With the development of society and the economy, living conditions have become more affluent and lifestyles have changed, leading to an increase in the consumption of high-fat, high-calorie foods due to the flood of easily accessible snacks, snack foods,

fast food, beverages, and so on.

As lifestyles have become more convenient, children take cars instead of walking to and from school, and after school they have almost no free time because of extracurricular lessons such as private academies. Even when they do have free time, they spend most of it indoors playing electronic games or watching television and videos, which reduces opportunities to burn energy by running around and exercising, leading to a lack of physical activity.

As the number of nuclear families and working mothers has increased, there are no adults to control children’s eating habits during the day, which increases children’s consumption of instant foods.

3. Energy Imbalance

Ultimately, the main cause of childhood obesity is that the energy consumed through meals, snacks, and so on is greater than the energy expended through activity. Most of this excess energy is converted into fat and stored, leading to obesity.

2. Symptomatic Obesity

Symptomatic obesity refers to obesity that occurs secondarily due to another disease. In such cases, treating the underlying disease must come first in order to treat obesity, so it must be distinguished from simple obesity. The causes of symptomatic obesity include the following diseases, and its frequency is very rare, accounting for less than about 1% of all obesity cases. If an obese child’s height is below the 5th percentile, or if there are abnormal findings such as delayed mental development, nervous system abnormalities, genital malformations, or external deformities, the possibility of symptomatic obesity is high.

1. Central Obesity

A disorder of the brain’s appetite-regulating area (the hypothalamus) due to the aftereffects of a brain tumor, head trauma, encephalitis, etc., causing excessive appetite, or an abnormality in the central mechanism that senses satiety, preventing the feeling of fullness

2. Endocrine Obesity

Cases caused by excess or deficiency of hormones secreted by the adrenal cortex, thyroid gland, gonads, etc., such as hypothyroidism, growth hormone deficiency, Cushing syndrome, and so on

3. Hereditary Obesity

Prader-Willi syndrome, Bardet-Biedl syndrome, Turner syndrome, Alström syndrome, etc.

3. Classification by the Characteristics of Fat Cells

Obesity can be divided into three types according to the characteristics of fat cells. In other words, it can be classified into the fat cell hyperplasia type, in which the size of the fat cells is normal but the number of fat cells increases; the fat cell hypertrophy type, in which the number of fat cells is normal but the size of the fat cells increases; and the mixed fat cell type, in which both the number and the size of fat cells increase.

In infancy and childhood obesity, the fat cell hyperplasia type is common, while in adults, the fat cell hypertrophy type is more common. In obesity that progresses from childhood to adulthood, it becomes the mixed fat cell type. In the case of fat cell hypertrophy, that is, adult-type obesity, severe obesity is rare, and when weight is reduced, the size of the fat cells decreases. However, in the case of the fat cell hyperplasia or mixed type, even if weight is lost, the increased number of fat cells does not decrease, so recurrence is likely. In addition, it often becomes moderate to severe obesity, which makes the problem more serious.

So far, I have explained the causes of childhood obesity.

In the next part, we will look at the symptoms and complications of childhood obesity.

Source: Korea Disease Control and Prevention Agency National Health Information Portal