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Origins - The origins of the Body Mass Index date back to the 1830s, when a formula was created by Belgian academic Lambert Adolphe Jacques Quetelet.

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Adolphe Quetelet - Despite having worked as an astronomer, mathematician, statistician, and sociologist, Adolphe Quetelet, did not have a background in medicine.

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Quetelet’s Index - Quetelet collected information on different populations, but primarily, white European ones. Stats of Scottish and French participants were initially used.

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Average man - The calculation was first aimed at identifying the measurements of the “l’homme moyen,” the average man.

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Average man - But his "average man" was an ideal. According to Quetelet, "If the average man were completely determined, we might consider him as the type of perfection; and everything differing from his proportion or condition, would constitute deformity or disease".

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Average man - His methodology failed to consider a much larger sample, which would have consequently changed the results.

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Different purpose - The index was used to measure people for statistical purposes, not as an indicator of body fat or health.

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Life insurance - It was not until life insurance companies started to use measurements of height and weight in the early 20th century that it became a health measurable tool.

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Life insurance - The measurements were essentially used to access health risk and determine how much people would pay for life insurance.

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Life insurance - But criteria such as frame size and age were not included in some of the tables.

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Name change - Researcher Ancel Keys, who led research in this field, renamed Quetelet’s Index the “Body Mass Index.”

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Other methods - Other methods were tried in the 1970s, but research concluded that Quetelet’s Index was "at least as good as any other relative weight index as an indicator of relative obesity."

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Other methods - Other methods included water displacement and skin calipers.

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How to calculate your BMI - The formula is simple. BMI = kg/m2.

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Doctors started using it - Despite being flawed and not based on medical science, physicians started using these measurements to assess patients’ health.

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How is it scored? - BMI readings under 18.5 means you are underweight. If you’re between 18.5 and 24.9, you’re considered normal.

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How is it scored? - If you’re between 25 and 29.9, you’re considered overweight. A BMI of 30 or higher, gets you qualified as obese. Above 35 and you're considered to be at higher risk for health problems.

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What BMI can't tell you - The formula is unable to measure how weight is distributed in the body. Body fat percentage is the indicator of obesity and BMI is unable to assess it.

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What BMI can't tell you - BMI is unable to distinguish between fat and muscle.

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What BMI can't tell you - Because muscle is denser than fat, a person carrying some muscle mass can be half the size of an obese person and weigh the same. As such, a muscular person may be classified as "overweight" or "obese."

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What BMI can't tell you - BMI is unable to distinguish between different types of fat. While subcutaneous fat is visible, visceral fat sometimes is not. Visceral fat is present in the muscles and around organs, and can be more detrimental to health than subcutaneous (beneath the skin) fat.

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What BMI can't tell you - BMI is unable to assess bone weight. Some people have a heavier "frame," and that reflects on the scales.

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Why do doctors still use it? - Many use it because it's easy to calculate, it's cheap, and can be done during consultation.

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In an ideal world - An MRI or a DEXA scan would give a much clearer picture of body fat, muscle, and bone percentages, but these are expensive exams.

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Alternatives - Waist circumference is already being used by many doctors worldwide. It can be an additional indicator.

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Alternatives - Wrist circumference, particularly in children, can also be used as an additional indicator.

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Fat is complex - Different types of fat and their relationship with health is more complex than a simple height x weight measurement.

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Obesity is complex - Other indicators should be taken into account. Blood and urine tests should be conducted as part of a thorough assessment to get the full picture.

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See also - You also need to be careful how you lose weight. Check out the dark side of extreme weight loss.

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