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Body mass indexThe body mass index (BMI) or Quetelet Index is a quotientof body mass which takes into account both height and weight measured as kg/m2;
It was originally developed between 1830and 1850by the Belgianpolymath, Adolphe Queteletduring the course of developing "social physics", and despite its age, the concept of the body mass index is still used today by government health bodies to see trends in health and illness, particularly relating to obesity.
UsesStatistical deviceImage:Body mass index-weightheight.jpg The Body Mass Index is generally used as a means of correlation between groups related by general mass and can serve as a basic means of estimating adiposity. However, the duality of the Body Mass Index is, that, whilst easy-to-use as a general calculation, it is limited in how accurate and pertainant the data obtained from it can be. Generally, the Index is suitable for recognising trends within sedentary or overweight individuals because there is a smaller margin for errors [{{fullurl:Template:FULLPAGENAME}}#endnote_jeuken]. This general correlation is particularly useful for consensus data regarding obesity or various other conditions because it can be used to build a semi-accurate representation from which a solution can be stipulated, or the RDAfor a group can be calculated. Similarly, this is becoming more and more pertinent to the growth of children, due to the majority of their exercise habits. [{{fullurl:Template:FULLPAGENAME}}#endnote_barasi] The growth of children is usually documented against a BMI-measured growth chart. Obesity trends can be calculated from the difference between the child's BMI and the BMI on the chart. However, this method again falls prey to the obstacle of body composition: many children who are generally born, or grow as an endomorph, would be classed as obese despite body composition. Clinical professionals should take into account the child's body composition and defer to an appropriate technique such as densiometry. Although the BMI is a relatively simple and quick process for calculating overall body mass, as with any data estimation that spans masses there are likely to be anomalies and errors of ranging proportion. Clinical practiceBMI is typically used as a means of estimating body mass, and can be calculated without the need for any equipment other than those for measuring height and weight. BMI can have a varying margin of error due to the fact that it is merely a rough estimate of body mass which does not take into account factors such as body composition or muscular mass. [{{fullurl:Template:FULLPAGENAME}}#endnote_jeuken] Despite this inaccuracy, the BMI is generally regarded as accurate when calculating if a sedentary individual is classed as obese, and has been used by the WHOas the standard for recording obesity statistics since the early 1980s. The reasoning for the use of the BMI in sedentary individuals is because body composition is thought to be a lesser factor; the use of other, more advanced body composition techniques would be seen as extraneous. Patients who are young or elderly, underweight or have high muscular mass would create fluctuations in the accuracy of the results from using the BMI, due to differentiations in muscular mass, or bone density (within children). In such cases, any doubt would result in the practitioner deferring to other techniques as a means of attaining more accurate results. If the correct mass of an individual is essential; e.g. in the case of a calorie or energy controlled weight-gain diet, then more accurate tests such as a skinfoldmeasurement or bioelectrical impedance analysiswould be required. ProblemsThe duality of the Body Mass Index is that, whilst being an easy-to-use quotient for body mass of sedentary individuals, it is a very imprecise calculation outside of sedentary groups. For example; comparison of a bodybuilder and a sedentary or obese individual of the same weight and height would produce similar results, which would be designated obese; regardless of the body composition of either. As a general rule, developed muscle contributes more to weight than fat; and it is through this fact that the body mass index can be readily classed as widely erroneous. It could be stipulated that long-distance or endurance athletes would be classified as underweight, despite the fact that the individual could be widely regarded as the perfect composite for their particular sport. However, within professional practice, body composition for athletes would not be calculated using the body mass index, and would most likely be done using an amalgamation of skinfold measurements and bio-electical impedance analysis. StandardsThresholdsHuman bodies rank along the index from around 15 (near starvation) to over 40 (morbidly obese). This statistical 'curve' is usually describedusing more familiar categories for easier comprehension by health professionals; eg, severe underweight, underweight, optimum weight, pre-obese, obese, morbidly obese. The exact index values used to determine weight categories vary from authority to authority, but in general a BMI less than 18.5 is underweight and may indicate malnutrition, an eating disorder, or other health problems, while a BMI greater than 25 is overweight and above 30 is considered obese. These range boundaries apply to adults over 20 years of age. The U.S. National Health and Nutrition Examination Survey of 1994indicates that 59% of American men and 49% of women have BMIs over 25. Extreme obesity — a BMI of 40 or more — was found in 2% of the men and 4% of the women. Body mass index calculations are not just for adults—they can also be used to identify the growing number of overweight children. BMI for children aged 2 to 20 years is calculated just as it is for adults, but it is classified differently. Instead of set thresholds for underweight and overweight, it is their BMI percentilethat is important. For children, a BMI that is less than the 5th percentile is considered underweight and above the 95th percentile is overweight. Children with a BMI between the 85th and 95th percentile are considered to be at risk of becoming overweight. Recommended thresholdsGiven the reservations detailed above concerning the limitations of the BMI as a diagnostic tool for individuals, the following are common definitions of BMI thresholds: Males
Females
VariationsThese recommended distinctions along the linear scale may vary from time to time and country to country, making global, longitudinal surveys problematic. In 1998, the U.S. National Institutes of Healthbrought U.S. definitions into line with WHOguidelines, lowering the normal/overweight cut-off from BMI 27.8 to BMI 25. This had the effect of redefining approximately 30 million Americans, previously "technically healthy" to "technically overweight". The WHOuses the term "pre-obese" where the USA uses "overweight". It also recommends lowering the normal/overweight threshold for South East Asian body types to around BMI 23, and expects further revisions to emerge from clinical studies of different body types. For Asians, the new cut-off BMI index for obesity is 27.5 compared with the traditional WHO figure of 30. An Asian adult with a BMI of 23 or greater is now considered overweight and the ideal normal range is 18.5-22.9. Singapore BMI Cut-offs References
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cs:Index t?lesné hmotnosti da:BMI de:Körpermasseindex es:Índice de masa corporal fa:????? ??? ??? fr:Indice de masse corporelle he:BMI hr:Indeks tjelesne mase it:Indice di massa corporea ja:??????? ms:Index Jisim Badan nl:Body mass index pl:BMI sk:Index telesnej hmotnosti sv:BMI th:??????????? vi:Ch? s? kh?i c? th? zh:?????? Categories: Mass| Nutrition| Obesity
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