Physiology

The Body Mass Index

Details

Parent Category: Physiology

Category: Physiology

Published on Thursday, 24 September 2009 08:22

Written by Luca Salvatelli

Obviously, then, the two values are different between them, as different are the aims that this index is to be reached: physical well-being first, best performance of the other. Over the years, several researchers have developed a set of formulas, which have found more or less successful, not because of the professionalism of those who had developed, but to the objective difficulty of establishing a unique measurement meters. One of the first formula used was the formula Bernhardt, much in use up to 50 years ago. This considered the ideal weight of a person that you value by multiplying the body height in cm with a chest circumference and then dividing by 240.

Bernhardt formula: ideal weight in kg = height in cm X chest circumference in cm / 240

This formula, although in its validity does not take into account the subject's age, his sex, a key element, and obviously does not take into account any sporting activity of the subject. It was later used Broca formula, still used by many, that includes a demonstration of ideal weight by body height in cm - 100 ± 10% or 20%.

Broca formula: ideal weight in kg = height in cm - 100 + / - 10-20%

Even this formula does not take into account the age of the subject, his sex and his physical activity, also fails to provide a unique value, but at a range of values large enough (+ / -20%).

In the Lorentz formula for ideal weight is obtained as follows:

Ideal weight (kg) = Height (cm) - 100 + ((Height - 150) / 4)

The formula Vague divided the subjects into Brevilinei and slender, then using the formula of Lorenz

Weight = Brevilinei Lorentz + ((((D.bio. D.bitr +.) / H) -0.45) x 1000) / 4

Weight = longilineal Lorentz + ((((D.bio. D.bitr +.) / H) -0.44) x 1000) / 3

D.bio. = Diameter biomerale

D.bitr. = Diameter bitrocanterico

Height = height (cm)

In this case it was sought to overcome one of the major defects of the formula of Lorentz.

The formula Perrault, divided the subjects into men and women:

Male Weight (kg) = Height (cm) - 100 - ((age - 20) / 4)

Female Weight (kg) = 0.9 X [height (cm) - 100 - (età/10)]

The index Pigneto offers an index on the type of morphological formation of the subject:

Pigneto index = height - (weight (kg) + thoracic circumference)

The same Pigneto has created a scale of morphological constitution:

Very strong up to 10.9

High 11 to 15.9

Fair From 16 to 20.9

Average 21 to 25.9

Weak From 26 to 30.9

Very weak from 31 to 35.9

Very mediocre Over 36

There is also a formula of the optimum weight used by insurance companies to calculate the weight and establish a greater or lesser incidence of disease and a greater or lesser expectation of life: ideal weight (kg) = 50 + 0.75 x height (cm) - 150

Weight index of Livi is still used today in medical school and in the selection of sports and military constitutionally classify subjects

I = 100 x weight (g) / height (cm)

Constitution class

Very thin Up 21.9

Thin From 22 to 22.9

On average 23 to 23.9

Fat From 24 to 24.9

Obese 25 onwards

Anthropometrics in contrast, is used often to calculate the ideal weight for height over the structure of skeletal or body size by measuring the circumference of the wrist or the transverse diameter of the elbow.

Body Circumference of right wrist. (cm)

Slender physique or light <16 <14

Normolinei size or average 16-20 14-18

Brevilinei or heavy body> 20> 18

The size can also be calculated in accordance with Grant from the report:

Stature (cm) / wrist circumference (cm)

Size Male Female

Hexyl> 10.4> 11

Media 9.6 - 10.4 10.1 - 11

Robusta <9.6 <10.1

According to the measurement of transverse diameter of the elbow (cm) The subjects are classified by size:

Hexyl Media Robusta

Male <6.7> 6.7 and <8.1> 8.1

Female <5.8> 5.8 and <7.2> 7.2

Once you have determined the body size you can estimate the ideal weight:

Brevilinei weight (kg) 75 x height (cm) - 58.5 68 x height (cm) - 51.5

Normolinei weight (kg) 75 x height (cm) - 63.5 68 x height (cm) - 58

Slender weight (kg) 75 x height (cm) - 69 68 x height (cm) - 61

All indices are reported here for its scientific value and without any doubt be used to select and classify a large number of subjects, but are certainly not suitable for analyzing the physical constitution of a subject in a unique and undeniable.

Among the various systems for calculating the ideal weight is now widely used in the medical field, the Body Mass Index, which was approved by the World Health Organization: This analyzes the mass of the subject in kilograms per square meter, the surface of the body is approximated as a square of side equal to.

The mass is in kilograms and height in meters.

 

Is a scale determined according to body mass that identifies the shape of the subject. This scale is unfortunately not unique, since, to the initial development by the World Health Organization since been joined by others with different values, even if only slightly. These two tables currently used by nutritionists and doctors Italian:

 Table Men

Table women 

As we can see the data differ, though not so obvious. Obviously this system of calculating the weight lends itself to some criticism, but it is worth pointing out that his study and its development has been made for medical purposes, such as prevention of obesity, identified as responsible for many serious diseases and also serious situation underweight. Among all the indexes listed is the one most used today in medicine. This index is useful, therefore, to assess cardiovascular risk and overall mortality and expectations for survival in extreme cases of under weight (BMI <18) and over weight (BMI> 40), while within the limits reported between 20 and 25, the scientific debate is still open. It is believed that it is not possible to determine an optimal weight in relation to health and to life expectancy. Unlike the discourse of the scientific community sports, where it is established that it is possible to define an ideal weight that maximizes the performance. In fact, the Body Mass Index, by itself, is not a valid indicator of weight, it is clear that two people of the same height and with the same weight, but a sedentary and the other professional sports have bodies and especially a quantity of fat mass very different. So although having the same BMI, the one, the sedentary, have a significant content of fat, the other, the athlete will be in perfect shape. Thus the objective of the assessment made by the specialist becomes crucial, as a careful analysis of the% of fat mass of the subject. So if the various mathematical formulas can help you select and frame a subject in a particular category anthropometric is much more difficult to establish them through his physical fitness. The need for weighted analysis of the subject and a series of individual examinations.