Everything You Should Know About the Body Mass Index

The Body Mass Index (BMI), also known as Quetelet II, is a quick and easy method for calculating one's own body mass index. It is used to assess the presence of obesity and can also be used to evaluate the risk of developing civilizational diseases associated with excess body weight, such as diabetes, stroke, or cardiovascular disease. BMI is frequently used as an indicator in scientific studies to determine the relationship between body weight and the occurrence of specific diseases. However, it should be noted that BMI may not be accurate for athletes and those who engage in regular physical activity due to increased muscle mass.

The body mass index is an excellent and straightforward way to determine if our weight is within the norm. Essentially, we are dealing with calculating the ratio of body weight (in kilograms) and the square of body height (in meters). As you can see, BMI can be easily calculated at home. Nowadays, thanks to the easy access to the internet, it is very simple to find conventional online calculators that not only calculate but also immediately provide a specific value of the indicator. Some of them contain indications whether our body weight should be reduced to achieve an optimal weight. Furthermore, there is a modification of BMI called Body Mass Index Prime, which is the ratio of a person's BMI and the upper limit of the norm, i.e., 25. The obtained value indicates the percentage of excess or underdeveloped fat tissue.

– below 0.74 – underweight; – from 0.74 to 1 – healthy weight; – above 1 – overweight. Norms for the Body Mass Index (BMI) have been developed based on data published by the World Health Organization (WHO). Two types of classifications are currently used for the values obtained in BMI calculation:

Below 18.5: underweight; from 18.5 to 24.99: normal weight; above 25: overweight. Additionally: below 16: malnourishment; from 16 to 16.99: significant weight loss; from 17 to 18.49: underweight; from 18.5 to 24.99: normal weight; from 25 to 29.99: overweight; from 30 to 34.99: grade I obesity; from 35 to 39.99: grade II obesity (tzw. clinical counselling); above 40: grade III obesity. It is important to note that BMI measurement is not recommended for children due to the continuous changes in body weight and height that occur during the growth process, which lasts up to about 16 years of age. To address this issue, specialists have developed a so-called percentile grid, which allows the weight of a child to be compared with that of their peers of the same gender. The results obtained based on this analysis are interpreted as follows: below 5 percentile: underweight; between 5 and under 25 percentile: thinness; between 25 and under 85 percentile: normal weight.

There are conflicting opinions on the significance of calculating BMI for men and women. Some individuals believe that computing BMI for adults is not particularly essential. The aforementioned formula is universal, encompassing both women and men. However, exceptions are evident, including groups mentioned above, such as pregnant women, athletes, and children under 14 years old. Nevertheless, there are sources that emphasize that obtained values should also be interpreted considering gender and age. The interpretation of the results is presented in the tables below.

As can be observed, the above-mentioned differences are not so striking that one could assert that gender has a substantial impact on the calculation of values. The Body Mass Index constitutes a universal and readily accessible method to calculate one's own body mass index. The calculation itself is very straightforward, and thanks to the calculators that are prevalent on the Internet, one could say that it is extremely simple. However, it is crucial to bear in mind that the results obtained using this method are not 100% certain. In order to confirm the results, I recommend consulting with a dietitian or another nutrition specialist.