Deceptive body Mass index
Each of us has repeatedly encountered the so-called body mass index (BMI), which is widely used to approximate the correspondence of a person's body weight to his height. The body mass index is calculated using a simple mathematical formula proposed in the 1830s by the Belgian scientist Adolphe Quetelet and consisting in dividing body weight in kilograms by the square of height in meters.
However, Nick Trefethen from the Institute of Mathematics, part of the University of Oxford, argues that this formula is fundamentally wrong. According to him, if all three dimensions of a person's body increased proportionally as he grew, the formula "body weight/height in a cube" would be the most adequate. However, this is not the case! But the formula "body weight/height squared" is also unrealistic. A more adequate approximation to a complex reality is a formula that looks like "body weight/height to the power of 2.5".
The use of the modern formula causes misunderstandings and is misleading, since people of low stature receive an underestimated value of the final indicator, and people of high stature receive an overestimated value. Accordingly, they cannot adequately assess the parameters of their body.
The Quetelet formula was developed at a time when people had neither computers nor calculators at their disposal, so a certain simplification looks reasonable. Moreover, in those days the problem of obesity simply did not exist. Especially strange in this situation is the attitude of healthcare institutions that continue to use the outdated approach everywhere. The reason for this, according to Trefeten, most likely lies in the fact that no one wants to "rock the boat."
As an alternative to the outdated formula , Trefeten offers the following option:
BMI = 1.3 x weight (kg) / height (m)2.5If you replace the traditional version of the formula with a new one, the body mass index of people of average height will practically not change, while low people will automatically get fatter, and high people will lose weight.
Trefeten notes that in our world puzzled by excess weight, this will upset some people of small stature and will be good news for tall ones, but in the long term, possession of adequate information should have a positive effect on people's health.
An interesting fact is that Quetelet himself was aware of the fallacy of the formula he proposed. In 1842, in his book "A Treatise on Man and the Development of his Faculties" ("A Treatise on Man and the Development of his Faculties"), he wrote: "if a person increased in all dimensions evenly, his weight at any age would correspond to the cube of his height. However, this is not what we observe in reality. The increase in body weight occurs more slowly, with the exception of the first year of life, when the above ratio actually takes place. However, at the end of this period and almost before reaching puberty, the increase in body weight approximately corresponds to the square of growth. During puberty, the rate of weight gain increases significantly again and almost stops after 25 years. In general, we will not make a gross mistake if we assume that in the process of development at different ages, the square of a person's body weight corresponds to the fifth degree of his growth."
On the other hand, many experts are of the opinion that the ratio of waist circumference to height is a much more adequate indicator than the body mass index. According to their recommendations, the waist circumference should be less than half the height.
An example of the erroneous application of the body mass indexConsider the case of two men with a height of 183 cm.
One of them spends all his free time on the couch, does not exercise and weighs 92 kg. His BMI = 27.
The second man is an Olympic champion in short–distance running, subject to incredible physical exertion. He weighs 96 kg, and his BMI = 28.
Based on the calculated data, an Olympic athlete is "fatter" than a lover of spending time on the couch, which is an obvious mistake. The reason for this lies in the inability to estimate the ratio of fat and muscle tissue in the body using the body mass index. As you know, muscle tissue weighs much more than adipose tissue of the same volume.
According to universally accepted criteria:
- BMI = 18.5-24.9 corresponds to normal body weight;
- BMI = 25-29.9 indicates the presence of excess weight;
- BMI = 30 or more means obesity.
What is the ideal body weight?Everyone would like to know how much they should weigh and how to calculate it on their own.
However, unfortunately, the ideal weight cannot be determined using a simple mathematical formula, as it depends on a number of factors, such as general health, height, the ratio of muscle and adipose tissue, bone density, body type, gender and age.
The body mass index can give a person a general idea of how much he should weigh, however, as can be seen from the article, this formula is very far from reality. It can be used in the study of large populations, but not in relation to individuals. Simultaneous assessment of the ratio of waist circumference to height may bring a little clarity, but this is not enough to get a complete picture.
Evgeniya Ryabtseva
Portal "Eternal youth" http://vechnayamolodost.ru based on the materials of the University of Oxford: Does my BMI look big in this? and Medical News Today: BMI – Is The Body Mass Index Formula Flawed?
Portal "Eternal youth" http://vechnayamolodost.ru04.02.2013