BODY MASS INDEX: HOW TO CALCULATE BMI AND WHY - IN SHAPE

Body mass index (BMI)

In fact, weight imbalances are something much more complex than a simple aesthetic problem.

Weight is closely linked to our health and a weight imbalance of body weight, whether it is obesity, overweight or excessive thinness, can be related to the onset of cardiovascular diseases.

The body mass index is a more reliable figure than the simple number on the scale, because it evaluates the general build of an individual and allows you to calculate the risk of disease and mortality due to overweight.

Body mass index definition

Also called the Quetelet index, from the name of its inventor, the body mass index was developed in the 19th century and is calculated by dividing the weight (expressed in kilos) by the square of the height (expressed in meters).

The mathematical formula of the body mass index is therefore this:
BMI = Weight in kg ÷ height in meters²
For example, an adult who measures 1.75m and weighs 70kg will have a BMI of 70 / (1.75 X 1.75) = 22.9

To then understand the value of this number resulting from the mathematical formula, it will be necessary to compare it to a series of reference values:

Less than 18 = thinness
Between 18 and 24.9 = normal constitution
Between 25 and 29.9 = overweight
Between 30 and 39.9 = obesity
More than 40 = morbid obesity

That is, the adult in the example is of normal constitution and has no cardiovascular risks related to body weight.

The limits of the body mass index

Although it is quite effective in revealing the problems of overweight and the risks associated with it, the BMI cannot be applied to everyone since it does not take into account either muscle mass or bone mass.

Some athletes have a high BMI, without necessarily being overweight, because muscles are heavier than fat.

Similarly, BMI must be taken with a grain of salt in the case of children, pregnant or nursing women, the sick or the elderly.

To have more precise results, it is better to perform some complementary tests such as anthropometry (which dissociates fat mass and lean mass) or measuring the thickness of the skin folds (using a caliper for certain parts of the body such as the belly) .