Body mass index or BMI is the quantification of a person’s tissue mass that includes muscle, fat and bones, cludes muscle, fat and bon to identify if heshe is underweight, normal, overweight or obese.There is a statistical correlation between body weight and the risk of certain afflictions like heart diseases, high blood pressure or type 2 diabetes. The BMI is calculated by di BMI is calculated by dividing a person’s weight in kilogrammes by the square of hisher height in metres.For instance, the BMI of a person who is five feet and 10 inches (1.78m) tall and weighs 95 kg will be 30.1 kg square metre. If pounds and nches are used to express weight and height, then the result has to be multiplied by he conversion factor of 703 to get the BMI.
Since when is the BMI used as one of the measures of obesity and health risks?
Belgian statistician Adolphe Quetelet was the first to propose a relation between weight and height and devised an index to mea sure obesity . Quetelet ana ysed height and weight data o conclude that other than he period of growth after birth and during puberty, the weight of a person increases proportionately with the square of height and hence an index could be devised to get the ideal ratio. This index was known as the Quetelet index before being rechristened the BMIin 1972 by Ancel Keys. It is interesting to note that the perception of obesity as a disease is about a century old, as for much of human history body fat was considered a sign of good health. It is believed that the first attempt to link obesity with mortality was done by actuaries of the insurance industry , who noted that there were increased death claims from obese policy holders. Today , the World Health Organisation considers obesity a global epidemic.
How is BMI interpreted?
The most cited interpretation classifies a person underweight if the BMI is lower han 18.5 kgsquare metre.People with a BMI ranging between 18.5 and 24.9 kgsqm are considered normal while hose who have a BMI of 25.0 9.9 kgsqm come under the overweight category . If the BMI is over 30.0 kgsqm, the person will be classified as obese. These BMI cut-offs are used for measuring the general health of people (both male and female) who are over 20 years of age as there are different yardsticks to measure obesity in children.Also, it has been noticed that hese cut-offs may not be appropriate for people who are 65 years old or above.
What is the basis of this interpretation?
The basis of normal BMI is derived from statistical data obtained by comparing differ ent sets of BMIs with obesityrelated diseases. The most frequently used interpretation of BMI, however, is derived from observing European and American populations, and experts have pointed out certain anomalies when using the same yardstick for other population groups. For instance, it has been observed that some Asian populations with a specific BMI have a higher proportion of body fat as compared to European populations with the same BMI.That means an Asian who is classified as overweight by this standard might actually be obese and will be at a higher risk of obesity-related diseases. Similarly, some Pacific islanders have a lower proportion of body fat at these BMI cut-offs.