The causes of obesity can be simply listed as:-
The vast majority of cases of obesity are due to excessive food and physical inactivity, but if your parents were obese, your chances of also being obese are greatly increased.
Some people have very efficient bodies (like a fuel efficient car), and require remarkably little energy in the form of food to remain healthy and active.
If the amount of energy used (calories/kilojoules) in exercise and normal body function exceeds the amount of energy taken in as food and drink, the person will always lose weight. If the reverse is true, weight will increase. It should be remembered that calories and kilojoules are a measure of the energy content of food, and not the fat content.
Middle age spread occurs as the metabolic rate of the body (the rate at which all organs in the body function) slows with age, at the same time that exercise levels tend to reduce, and food intake increases with more leisure and security. Many women gain weight after the menopause due to a slowing of the body’s metabolic rate when oestrogen levels drop. This effect may be slowed by hormone replacement therapy.
Other metabolic causes of obesity include:
- disorders of the pituitary gland under the brain (caused by a tumour, cancer, stroke, infection, injury or other disease),
- an under active thyroid gland (hypothyroidism),
- Cushing syndrome (over production of steroids, or taking large doses of cortisone),
- poorly controlled insulin dependent diabetes,
- the chromosomal defect of Prader-Willi syndrome,
- metabolic syndrome (also known as Reaven syndrome and insulin resistance syndrome),
- Stein-Leventhal syndrome (multiple cysts in the ovaries),
- Fröhlich syndrome (late onset of puberty, thin wrinkled skin, scanty body hair)
- Laurence-Moon-Biedl syndrome (night blindness, intellectual disability, obesity, small genitals and sometimes extra fingers or toes).
Obesity can be self-perpetuating as one of the effects of fat is to insulate the body so that it does not lose as much heat. If less heat is lost, less heat needs to be produced within the body, so the metabolic rate drops, less energy is required for the body to function and excess energy is stored as fat, thus completing the cycle.