*The body-mass-index (BMI)*– is a measure of the evaluation of the body weight of a person in relation to his height. It was developed in 1832 by Adolphe Quetelet.

The BMI refers to the body mass (or mass, colloquially known as weight) on the square of the height. The value “Square of height” is unrelated to the surface of the body. BMI is only a rough guideline, since he considered stature and gender, nor the individual composition of body fat and muscle tissue of a person.

**General calculation formula**

where the body mass (in kilograms) and height is (in meters).

Calculation of missing limbs (amputation)

There is an amputation, so you must calculate mt the theoretical body mass prior to the calculation of BMI:

For this, the following values are used:

Body correction factor k

Hand 0.008

Forearm 0.023

Upper arm 0.035

Foot 0.018

Lower leg 0.053

Thigh 0,116

Example

A woman was 56 kilograms, 20 years old and 1.70 m tall. Amputated the left leg of the woman, which is why the correction values for a lower leg and foot (logically also removed by amputation of the lower leg) are to apply. Their theoretical weight calculated thus as follows:

This mass can then be used in the normal BMI formula:

**interpretation**

**in adults**

Values of normal-weight people are m² and 24.99 kg / m² in accordance with WHO’s obesity classification between 18.5 kg / m sq, from a BMI of 30 kg / m obese individuals considered sq in need of treatment.

Age and gender play a major role in the interpretation of the BMI. Men have typically a higher percentage of muscle mass to the total body mass than women. Therefore, the lower and upper bounds of the BMI value classes when men are slightly higher than for women. So the normal weight is according to the DGE men ranging from 20 to 25 kg / m, while women inside ranging from 19 to 24 kg / m².

The Broca’s index is used for the assessment of an underweight such as anorexia. The diagnostic criteria of anorexia in adults a BMI ≤ 17.5 kg / m² provide in children and adolescents a BMI below the 10th percentile of the age.

*Examples*

A woman weighs 58 kg and 1.70 m tall. Your BMI is calculated as follows: 58 kg / (1.7 m · 1.7 m) ≈ 20 kg / m² ⇒ normal weight.

A man is 87 kilograms and is 1.76 m tall. His BMI is calculated as follows: 87 kg / (1.76 m · 1.76 m) ≈ 28 kg / m² ⇒ overweight.

**in children**

The BMI can be used also for children and infants as a measure for the healthy development of the child. The BMI is calculated using the same formula as the BMI of adults, however, the length lying down rather than the level of the standing is used in children less than 25 months. This may be up 0.7 cm longer than the height in the standing position, therefore the normal BMI range have a characteristic kink here in the tables. The child’s BMI is compared in the tables with the data of other children of same age. WHO publishes the BMI tables for boys and girl. A child with more than + 1 is considered as overweight standard deviation SD (corresponding to a BMI of over 25 in an adult), of whom are obese with more than + 2 SD (corresponding to a BMI of more than 30 in an adult). For children under the age of five, there are corresponding tables of the WHO.

A further possibility to calculate is so-called Percentile curve to go to, where is the ideal BMI on the average of the existing values. The child is considered of whom are obese, if it has a higher BMI than 97% (97. Alters percentage) his peers, underweight, when only 3% (3. Alters percentage) or less have a lower BMI.

The problem of this calculation basis is that that the definition for malnutrition would move, if changed the nutritional status of children in a society as a whole, for example through a famine, many children are undernourished, or if there are many overweight children. If by definition always exactly 15% of all children are overweight, you can’t get for example to say, 25% of all children are overweight.

The limits of an appropriate BMI strongly relate to the level of development of the child. So, for example, the rapid growth in the early stages of puberty and the like is shown. A child makes these stages earlier or later than the average, with also an according to the age group is too high or too low BMI can occur despite normal weight.

**Validity**

The use of BMI for the diagnosis of underweight or body fat fat induced obesity based on defined limits is very controversial. Because a relatively high body weight and thus a high BMI may be caused also by much muscle mass. Trained strength athlete without much body fat have a high BMI alone due to their lean muscle mass. Athletes of endurance (5 km run, 10 km run, Marathon), who participated in the Olympics in 1960 in Rome, have a BMI of 20-21, a BMI of 26-29 therefore the scale of what is considered normal weight, is adapted for the medical diagnosis of bottom and overweight if necessary strength athletes (weightlifting, Javelin, hammer and discus, shot putter). So, a reduction in the limit between normal and overweight by 30 kg / m2 to 22 kg / m2 was found, for example, for paraplegia.

In anthropometric history and historical anthropology of the average body-mass index of populations is similar to the height, used as indicator for the standard of living. Based on historical data collected such as the recruit patterns possible reviews in the past. Times past in next return estimates of BMI, which were conducted on bones from archaeological contexts. To them can be estimated, that the average diet in the early Middle Ages in Europe was quite good.

BMI of athletes. Sport; n: number of observations; medium height, weight and BMI.

**History**

The BMI was developed in 1832 by Belgian mathematician Adolphe Quetelet. The term body mass index (BMI) is a 1972 published article of Ancel keys. Keys recommended BMI only for the statistical comparison of populations, not for the assessment of overweight individuals. Through the use of BMI, meaning won U.S. life insurers who use this simple classification, so to calculate premiums for life insurance, that additional risks are taken into account by overweight. Since the early of 1980s, the BMI is used also by the World Health Organization WHO. The present BMI classification WHO is essentially since 1995.

The body-mass index as a criterion for the verb appointment in the public service will be used in some German Länder (Baden-Württemberg and North Rhine-Westphalia, for example). People with too high or too low BMI are not established. This arrangement was criticized in several times.

**Other indexes**

A number of other indexes exist in addition to the BMI. The Broca’s index and the Ponderal index are the most famous. The physique development index is suitable even for a biological age determination.

An eight-year study of the Munich Ludwig-Maximilians-University with over 11,000 subjects according to the relationship between waist circumference and height (“waist-to-height ratio”, waist–hip) is better suited for the assessment of health risks because here more accurate conclusions on the health concern belly fat can be drawn.

The WHR (waist-hip ratio, waist-to-hip ratio), which was originally introduced as a first and foremost body aesthetic measure also allows an assessment of the distribution of body fat. Another dimension is the surface of the body, often using the Mosteller formula calculated. As a result of this many mass being classified as overweight for the same person – varies depending on the total length and morphology – according to the formula of one or the other. As a more commercially-oriented, so-called vital analyses are to see.

The area is a further development of the BMI mass index (AMI), which takes into account the stature and the sex of an individual. Makes it easy to measure the waist circumference. He correlates well with the BMI and is therefore, in medicine and in the population often used to determine obesity.

**Body adiposity index**

The body adiposity index (BAI) is a method different from the body-mass index of to calculated or estimated the percentage of body fat. BAI takes into account also the hips as well as the length of the body. According to a study by 2012 of the Institute for nutritional research in Potsdam-Rehbrücke and the medical clinic IV of the University of Tübingen (the data of the Tübingen lifestyle of intervention program – TULIP – were used) he is now inferior until 2011 popular BAI BMI in its significance, because the BMI in a closer relationship to the distribution of body fat as the BAI – especially for men. The measured waist circumference, however, has a still higher significance about the body fat percentage as the BMI or BAI. Diabetes risk assessment of BMI was superior to the BAI, however, the waist had again a still higher significance again. BAI fails thus as an alternative to the BMI into consideration. Therefore, the measurement of the waist as a supplement to the determination of BMI is useful.

The BAI is calculated according to the formula:

BAI = (waist circumference in cm) / (m size) 1.5 − 18

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