Body mass index: what's wrong with the old method that has little to do with medicine

Many experts warn that the body mass index is a useful tool for medical statistics, but it is not always possible to determine the healthy weight of an individual.

ABC News explains why BMI is an outdated method, as well as the history of the non-medical origin of this technique.

It should be recalled that body mass index is calculated by dividing body weight by the square of height. The result should be a two-digit figure that places a person in one of three categories.

As you know, a figure below 18.5 seems to mean that you are underweight, from 18.5 to 24.9 is considered normal, and above 30.0 is considered obese. But, as experts note, this simplicity hides the fact that this method is not so easy to determine a truly healthy weight in each individual case. It is noted that BMI is more suitable for statistical calculations of a large population.

In support of this fact, it should be recalled that BMI has a non-medical origin, and was invented not by a doctor but by a mathematician in the 1830s. Interestingly, he was not looking for a method to quickly diagnose obesity, but rather to determine the ideal average weight of a person.

He took thousands of measurements and compared them to determine the average weight. However, his research was limited to weight measurements of men and had nothing to do with individual health.

It wasn't until the 1970s, when physiologist and nutritionist Ancel Keys and a group of his colleagues promoted the Ketle Index as the best available way to quickly identify obesity, that it became what we know today as BMI.

Disadvantages of BMI

According to the researchers, this method works really well when measuring large populations, but its effectiveness decreases at the individual level. Therefore, BMI provides only a rough estimate of a person's health status.

A vivid example of the ineffectiveness of BMI is athletes. Because the formula does not take into account the differences between muscle tissue, bone and fat, it turns out that most of them are overweight.

It is equally important that the calculations do not take into account gender, age and physique. There are also people in excellent health who are overweight, as well as those who fall into the "healthy" category but have metabolic problems.

In other words, BMI does not take into account the actual health of a person, which does not favour the effectiveness of this diagnostic method.

"If we can immediately stop labelling people unhealthy based on their BMI, it will help these people to improve their health," said nutritionist Fiona Willer.

Why BMI is still in use

According to experts, BMI is still an effective method for health departments or scientists conducting research on the health of a large population. Due to its simplicity and accessibility, calculations can be carried out quite easily.

What is the alternative?

According to experts, a more accurate test of weight will be to measure waist circumference, which is quite easy to do at home. To do this, a person is measured midway between the lower rib and the hip bone. This should be approximately where your belly button is located.

According to the Australian Institute of Health and Welfare, a waist circumference of more than 80 centimetres for women and 94 centimetres for men may indicate an increased risk of chronic disease.

This type of diagnosis is considered quite useful; fat deposits around the waist, known as abdominal or visceral fat, are the most dangerous. However, if a person notices that their waist size has changed, they should not immediately focus on it. Of course, it is important to monitor your weight, but such changes can be the result of age or hormones.

Therefore, doctors emphasise that it is more important to monitor your well-being, as well as try to maintain a healthy lifestyle and give up bad habits.

As OBOZREVATEL previously reported, nasal congestion leads to a decrease in the level of oxygen in the human blood, which causes fat to accumulate in the body. This leads to weight gain and even obesity.