Obesity can be defined as an excess of body fat that poses a health risk. The term is normally reserved to describe people who are grossly overweight, while the term overweight is more frequently used to designate mild degree of adiposity. Approximately 20% of excess over desirable weight imparts a health risk.
Consequences of Obesity:
Accumulation of adipose tissue in different areas has distinct consequences. Many of the important complications of obesity, including insulin resistance, diabetes mellitus, hypertension and hyperlipidaemia, are linked to the amount of intraabdominal fat rather than to lower body fat or subcutaneous abdominal fat.
Obesity is associated with increased levels of free fatty acids (FFA) which are due in large measure to the presence of more lipolytically active intraabdominal adipocytes. Increased level of FFA is associated with inhibition of hepatic clearance of insulin and thus with hyperinsulinism and its consequences.
Medical conditions associated with the more common obesity are hypertension, atherosclerosis, diabetes mellitus and hypoventilation syndrome; the less common ones include hepatic steatosis, gall bladder disease, osteoarthritis of weight-bearing joints and gout. The mortality is 10-12 fold higher in the morbidly obese compared to the general population
Obesity contributes to an increased incidence of cardiovascular disease not only directly but also indirectly by predisposing to hypertension, diabetes mellitus and hyperlipidaemia.
Obesity results in circulatory changes such as increases in pulmonary and systemic blood volume and increase in stroke volume and cardiac output. The increased workload on the heart leads to dilatation and hypertrophy which predispose to congestive cardiac failure. There is an increase in myocardial oxygen demand; when the supply cannot meet the demand, it results in infarction and death.
Obesity is associated with hypertension, which can be reduced with improvement in weight. Increase in cardiac output and peripheral resistance is responsible for the hypertension. There is evidence to show that both basal and stimulated levels of norepinephrine are increased in obesity. As the body mass increases, arterial pressure rises. Weight reduction not only improves the hypertension but also improves carbohydrate intolerance and hyperlipidaemia, thus diminishing the risk for coronary artery disease.
Obesity is a common association in NIDDM; however, in most developing countries obesity is seen in less than 50% of patients with NIDDM. Obesity predisposes to carbohydrate intolerance by increasing insulin resistance.
Significant alteration in pulmonary function occurs in the severely obese and is due to increased oxygen consumption associated with breathing. The extreme form of pulmonary dysfunction is obesity-hypoventilation syndrome which is characterised by somnolence, obesity and hypoventilation. The sleep apnoea in the obese may be central, obstructive or mixed. Pulmonary hypertension, polycythaemia and cor pulmonale result from prolonged pulmonary dysfunction.
In men, there is a consistent reduction in the concentration of total serum testosterone. In women obesity is associated with clinical symptoms suggestive of abnormal ovarian function, including irregular menstruation, secondary amenorrhoea, hirsutism, early menarche and delayed menopause. Both in pre and postmenopausal women, circulating androgens from the adrenal gland are converted to oestrogens in the peripheral tissue. This enhanced production of oestrogen in obese postmenopausal women may have a causative role in the high incidence of endometrial carcinomas and low incidence of osteoporosis. The serum free testosterone level has been reported to be elevated in obese women and this hyperandrogenemia is said to be responsible for the irregular menses and hirsutism.
Below 18.5 – Underweight
18.5 – 24.9 – Healthy
25.0 – 29.9 – Overweight
30.0 – 39.9 – Obese
Over 40 – Morbidly obese
BMI is not always an accurate way to determine whether you need to lose weight. Here are some exceptions:
- Body builders:Because muscle weighs more than fat, people who are unusually muscular may have a high BMI.
- Elderly:In the elderly it is often better to have a BMI between 25 and 27, rather than under 25. If you are older than 65, for example, a slightly higher BMI may help protect you from osteoporosis.