Excessive intake of calories
When excessively eat foods, the calories intake goes beyond the calories consumption, and the surplus calories are stored in the body, resulting in gaining weight by causing triglyceride accumulated in lypocytes.

Lack of exercise
When exercise is not performed enough, the basal metabolism decreases, resulting in gaining weight by being turned surplus energy into fat.

Psychological factors
Behavior pattern changed by psychological tension or conflict may cause obesity, which usually occurs due to dependent personality or avoidance of responsibilities. Also, there is the cases that stress from interpersonal relationships cause gaining weight.

Genetic factors
Studies have shown that, in many cases, when parents are obese, their children are obese. Also, along with genetic factors, parents' eating habits can be an important environmental factor which may cause obesity in their children.

Endocrine abnormalities
Obesity may be occurred when problems develop in the hypothalamus where the feeding center and the satiery center are. Cushing-syndrome, hyposhyroidism, decreased secretion of estrogen due to menopause may cause obesity as well.

Side effecs of medications
The side effects of medication which is taken for treatment of disease or birth control may cause gaining weight. Medication includes steroids(adrenal cortical hormone), tranquilizer, female hormone(estrogen), antidepressant, oral contraceptive, etc.

Genetic fator
In case of bingeing, reducing the number of meal time, or increasing meal to meal interval, insulin secretion increased and it leads to elevation of activity of fat synthesis enzyme, resulting in accelerating fat storing.
When the meal time is short, there is no time for the blood sugar level to rise enough to make appestat feel full, causing more food intake.

Lack of exercise
In case of being obese when young, the number of fat cells increases, and this number never decreased even after becoming adult.
When childhood obesity continues, it becomes morbid obesity in adulthood.

Psychological factor
Wrong eating habits such as overeating or unbalanced eating during pregnancy,
or During postpartum cooking, there is a problem in the recovery process, so obesity
It occurs when the state becomes stagnant.