Body Mass Index (BMI)

Clinical intent

The BMI measure was conceptualized by Adolphe Quetelet in On Man and the Development of his Faculties, or Essays on Social Physics published in 1842. For 130 years, the BMI was largely unevaluated and unused by the research community until 1972, when Ancel Keys, a nutritional epidemiologist and physician, identified this ratio as a suitable proxy for determining body fat percentages within the population [1]. The BMI is a convenient clinical and epidemiological metric for identifying and monitoring obesity prevalence [2].

Method of use

The patient is asked to provide weight in pounds and height in feet and/or inches.

Calculation

First, the total height in inches is calculated

total_height_in_inches = (height_in_foot * 12) + height in inches

Then the BMI can be calculated by dividing the weight by inches squared and then multiplied by 703.

BMI = (weight_in_pounds ÷ height_in_inches^2) * 703

Clinical interpretation

The BMI can be catagorized as follows:

• Severely underweight - BMI less than 16.5
• Underweight - BMI under 18.5
• Normal weight - BMI greater than or equal to 18.5 to 24.9
• Overweight – BMI greater than or equal to 25 to 29.9
• Obesity – BMI greater than or equal to 30

Asian and South Asian population:

• overweight - BMI between 23 and 24.9
• obesity - BMI greater than 25

Ethnicity as well as athletic status can influence the obesity risk and the catagorization based on BMI would need to be adjusted.[3]

References

[1] Keys A, Fidanza F, Karvonen MJ, Kimura N, & Taylor HL (1972). Indices of relative weight and obesity. Journal of Chronic Diseases, 25(6), 329–343.
[2] Frellick M (2013). AMA Declares Obesity a Disease.
[3] Weir CB, Jan A. BMI Classification Percentile And Cut Off Points. In: StatPearls. Treasure Island (FL): StatPearls Publishing; December 7, 2019.