It was first invented in the 19th century by a Belgian polymath called Adolphe Quetelet, hence it is also known as Quetelet Index.

BMI gained popularity as a body weight-tracking device in the mid twentieth century. This coincided with the time when obesity began to raise its ugly head in the more prosperous west. It became a tool whereby a doctor could actually guage a patient being too heavy or too thin and even discuss the issue with the individual.

To calculate BMI, you need to know your weight and height in kilo-grams and centimeters or meters. The weight of a person is then divided by the height.

If you only know your height and weight in inches and pounds the calculation is a little more complex.

A change in BMI over a short period of time is often used to measure the change in one’s lifestyle habits.

People of the same age and sex have different BMI depending on the amount of fat content in the body. However, with BMI, some exceptions apply to the general rules and there is the risk of both over- or under- estimating the total amount of body fat in an individual. Due to this shortcoming some researchers use it only as a tool for population measure.

Although not a perfect index in predicting health risks, BMI is able to predict the underlying risks in a large population and can be used as an early warning sign that can suggest if lifestyle changes are required or not.