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What is it?

Body Mass Index or BMI was created back in the 1800’s as an easy way to measure body fat calculated from height and weight. People that have an increased BMI are considered to be at high risk for diseases associated with more body fat.

Limitations

Although BMI can work as a great screening tool to assess large populations of people, it is not a perfect system. Since the equation to calculate BMI
is: weight (kilograms)/ Height (meters)2 it does not take into account that muscle and bone mass weigh more than fat. This can skew the results when it comes to more muscular individuals such as athletes. This also means it will not be a good measurement for pregnant women as well. BMI would be 28.5 (obese)

Measuring body composition

With the limitations of BMI, how can we get a more accurate picture of body composition? There are other ways to help calculate body composition and health risk such as waist circumference, waist to hip ratio, skinfold measurement, air displacement plethysmography, bioelectrical impedance analysis, etc. All of these methods can help to paint a fuller picture, but each one still has limitations. The gold standard however is Underwater weighing and dual-energy X-ray absorptiometry (DEXA). Although they are the more accurate way to measure body composition, they are much more difficult to perform.

Conclusion

Body Mass Index may not be a perfect tool, but it is an easy way to assess many individuals in a short time. Those with a higher BMI score are considered to be “more at risk” and further evaluation with these individuals may be necessary.

Dr. Kyle Wagner