The causes of obesity and pathogenesis
Over-intake of heat energy is beyond the requirement of human body, it store as excessive fat in the body but by the form of liver and muscle glycogen. The main form of heat energy stored is fat. Which also mainly for triglycerides, glycogen reserves are limited. If excessive neutral fats and sugars were ingested, it accelerates fat synthesis，as external causes of obesity. In the case of lacking activity, such as cessation of physical exercise, to alleviate physical labor or disease recovery rest in bed, postpartum recuperation, and obesity occurs. In general, there is a difference in intake of calorie every day. It depends on age, gender, height, labor factors. So that the body weight is relatively stable due to the precision adjustment of normal neuroendocrine, without the risk of obesity.
Obesity results from endogenous factors due to disorders of the fat metabolism
1. Hereditary factor，people with simple obesity may have family history. Obesity always consider being polygenic inheritance, heredity plays a role of easy occurring. Obesity has a close relation with lifestyle, ingestive behavior, hobby, reaction of insulin, social psychological factors.
2. Neuropychosis factors: There are two pairs of nerve nucleuses that related to ingestive behavior in human hypothalamus. One is abdominal contralateral nucleus, also known as satiety center; another is ventral lateral nucleus, also known as hunger center. When Satiety center is exciting, it feels full and do not want to eat food. Contrary, it increases appetite due to suffering damage. Hunger center is contrary to satiety center. It tries to get dynamical balance in maintaining normal body weight under physiological conditions though appetite regulation. The role of blood-brain barrier in the hypothalamus is relatively weak, resulting in a variety of biological activity factor in blood move to it easily, which impact on feeding behavior. These factors include: glucose, free fatty acid, norepinephrine, dopamine, 5 - serotonin and insulin. In addition, mental factor often affect appetite, Prey central function was in the control of the mental state. When the spirit hypertension produces the excitement or adrenergic nerve stimulation (especially α receptor dominant), appetite is in suppression. When insulin secretion increased due to the excitement of vagus nerve, appetite often gets better.
3. Hyperproinsulinemia, in recent years, hyperinsulinemia plays a dramatic role in causing obesity. Obesity often coexist with hyperinsulinemia, the causal relationship between them need to be further explored. But in generally, it is believed that obesity is caused by hyperinsulinemia. The people with Obesity due to hyperinsulinemic produce six times the normal level of insulin.
Insulin has a significant promote effect in fat accumulation. In a certain sense, it can be the monitoring of obesity factor. The roles of insulin promote body fat increased is to work through the following Steps: a. to promote glucose into the cell, and thus synthesis of neutral fat is done; b. suppresses the fat to be utilized in fat cells.
The coexistence of excessive feeding and hyperinsulinemia are often the important factors for obesity and maintain.
4. Abnormal brown adipose tissue, brown adipose tissue is a fatty tissue that has been discovered in recent years. It corresponds with white adipose tissue that mainly distribute in the subcutaneous and around the internal organs. Distribution range of brown adipose tissue is limited, it only distribute in the inter-scapular, the back of the neck, axillary region, mediastinum and around the kidney. The appearance of this organization is light brown; it has relatively small changes in cell volume.
White adipose tissue is a form of stored energy; the body stores the excess energy as the form of a neutral fat. The cell volume of white adipose tissue changes large with the energy release and the reservoir.
Brown adipose tissue is a thermogenic organ in function. That is, when the body ingestion or stimulate by cold, fat in Brown adipose tissue is burning, thus the level of the body's energy metabolism is determined. The two cases above are called heat produce by feeding, and heat produce by cold.
Thermogenes organizations of brown adipose tissue directly participate in the total adjustment of the heat in the body. It sends out the excess heat to the vitro, to make the balance of energy metabolism.
There is a little research on brown adipose tissue in human obesity, but it can be observed to part of obesity patients with the heat production dysfunction.
5. Other factor, for example, hormone is an important factor in the regulation of fat metabolism, especially in triglyceride synthesis and mobilization of decomposition. They changes in trends by enzyme regulation in hormones. Insulin and prostaglandin E1 are main hormones that promote fat synthesis and inhibit decomposition. Hormones which promote lipolysis and inhibit the synthesis are catechol amines, glucagon, ACTH, MSH, TSH, GH, ADH and sugars adrenal cortex hormones. When the former excessively secrete than the latter one, it can cause an increase in fat synthesis exceeds decomposition, thus obesity can be resulted. There is a close relation of endocrine factors and secondary obesity.