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  • These are my assistants, Coleman and Phil.

  • They're both around the same height, weight, and consequently, they have the same Body Mass Indexor BMI.

  • But if you split them open Damien Hirst style

  • or just compare the results of their body scans you can see a slight difference.

  • Phil has more body fat than Coleman, and Coleman has more muscle than Phil.

  • Although BMI is a popular measure to assess if a person's weight might be putting them at risk for obesity-related diseases, its results can be pretty misleading and less nuanced than we'd like.

  • So the BMI is an index that looks at somebody's body weight divided by their height.

  • So the formula is the body weight in kilograms divided by the height in square meters.

  • 18.5 and below is underweight, 18.5 to 24.9 is your healthy range, 25 to 29.9 is overweight, and a BMI over 30 is classified as obese.

  • With the idea being that the taller somebody is, the more they should weigh.

  • Kinda weird how a single decimal point can separate being overweight from being obese.

  • The major problem with using BMI as a marker of health when it comes to body weight, because it penalizes you if you have a lot of muscle and you're healthier.

  • Let"s use professional athlete Marshawn Lyncwh as an example.

  • He's 5'11, 215 lbs, and his BMI is 30.

  • He'd be categorized as obese.

  • That is because BMI doesn't distinguish muscle from fat.

  • We are really concentrating on how much muscle does somebody have, because muscle it's the metabolic engine.

  • It's the thing that burns calories and the more muscle you have

  • the easier it is for you to stay at a lower and

  • more healthy body fat percentage not necessarily a BMI.

  • In this way, BMI's reliability as an indicator of health breaks down for athletes like Lynch.

  • There are several more variables that can influence the interpretation of BMI.

  • Things like age, gender, and ethnicity.

  • While BMI is a useful measure for a large population study, for example,

  • to compare relative obesity rates from state to state;

  • it becomes more problematic when you use it to determine an individual's health.

  • The body mass index was introduced in the early 19th century.

  • This guy who created the formula — I'm so sorry, I'm gonna butcher his name,

  • Lambert Adolphe Jacques Queteletwasn't even a physician.

  • Quetelet was a Belgian mathematician.

  • And his reason for creating the formula was to study thenormal man”, not obesity.

  • Its use shifted to study obesity because of Ancel Keys.

  • In 1972, Keys used the formula in his "Indices of Relative Weight and Obesitystudy, renamed

  • the formula to body mass index, and from there thenewmeasure caught on among researchers.

  • Over the years, its use in the health professional field grew and it's pretty much stuck around since.

  • It's easy to use, cheap, fast, and its right about 80% of the time.

  • So even though BMI has stuck around for more than 200 years,

  • it's not the be-all and end-all indicator.

  • There are more effective ways to assess to body composition, and overall health.

  • Hydrostatic weighing, or underwater weighing, is an option.

  • Along with MRI scans, and waist-to-hip ratio.

  • Medical tests like checking blood pressure, your glucose levels, resting metabolic rate,

  • can further give a picture of overall health.

  • I went to George Washington University, and lab director Todd Miller showed me another way,

  • using dual-energy x-ray absorptiometry or DEXA image.

  • It measures total body composition, including fat mass, lean body mass, and bone density.

  • So the green is the areas where the body is very lean.

  • The yellow areas of moderate fat.

  • And the red areas of high fat.

  • So this person was here July 3rd she had 72 pounds of fat and 109 pounds of muscle.

  • And in December 27th of this year she had at thirty seven pounds of fat in 115 pounds of muscle.

  • Using this chart you can see if this person stepped on a scale, they'd only see they lost 29 pounds.

  • What the scale wouldn't say is that they gained six pounds of muscles,

  • and BMI wouldn't say that either.

  • So even if two people have similar BMIs,

  • that one number will never truly give either of them

  • the full picture of their overall wellbeing.

  • BMI is an indirect measurement of one aspect of an individual's health.

  • So while it can be helpful, it shouldn't be the only way to understand the human body.

These are my assistants, Coleman and Phil.

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What BMI doesn't tell you about your health

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    April Lu posted on 2018/12/13
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