Understanding the Body Mass Index


A person’s weight is an important measure used in different contexts and measures of health. Coupled with a person’s age and height, the weight is important for determining correct medicine dosages and alcohol tolerance levels. The weight of a person also features in the calculation of the body mass index or BMI. The BMI is frequently used to determine what is a healthy weight range for someone to have.

Measuring BMI

The BMI is a calculation performed using the weight and height of an individual. It is computed by dividing the weight of a person in kilograms by the square of their height in meters squared. The calculated value of the BMI together with the height and weight values are then found on a BMI chart. This shows in which range a person falls in terms of their weight. The BMI chart is divided into different segments, and depending on the calculated value of BMI, a person can find out if they have a healthy weight. They can see if they are underweight, normal weight, overweight, and obese, depending on which segment or range they fall in.

The Significance of the BMI

The measure of BMI is important in medical diagnostics as well as for measuring personal fitness. It gives a quick calculation but can provide some useful information immediately. The ranges are quite broad, so the limitations of the BMI must always be considered. A BMI that is below 18.5 kg/m2 signifies that the individual is underweight. A BMI that lies within the range of 18.5-25 kg/m2 means that a person is of normal weight. If the BMI is between 25 and 30 kg/m2, the person is overweight, and if the calculated value is over 30, it means that the person is obese.

The foundational work on the basis of the BMI calculation was done in the early 1800s by a Belgian mathematician, astronomer, and more, Adolphe Quetelet. The first use of the term Body Mass Index was much later in 1972 in a medical journal by Ancet Keys. In it, the case for the BMI was made. Among other bodyweight indices, the BMI was also found to be a satisfactory and useful measure of relative obesity. The BMI was found to be more ideal for looking at population studies, but with time, it has ground for use at an individual level as well.

BMI shows how thick or thin someone is. There are some limitations to it, depending on the lifestyle of the individual. Initially intended to measure weight issues in people with a relatively inactive lifestyle, it is natural that when used with athletes and others with a high muscle weight, the calculations can be a little skewed.

The World Health Organization (WHO) uses BMI to classify certain at-risk populations under its watch. The global body takes the value of 18.5 to make major health concerns. People below that BMI value are likely to be experiencing health issues or nutritional issues. The nutritional problems could be an eating disorder or malnutrition.

In addition to the four broad classifications of a person’s weight based on BMI, there are other sub-classifications that help with further analysis. An underweight person can be underweight, severely underweight, or very severely underweight. The obese range is further broken down into six classes of obesity from Class I to Class IV, indicating that an individual is moderately, severely, very severely, morbidly, super, or hyper obese.

In addition to the exceptions and limitations already discussed above, it should be noted that for children between the ages of 2 and 20 years, the BMI comparison is made differently. There are also some international variations in BMI calculations.

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