Additional Math Pages & Resources

Monday, January 10, 2011

New Year Questions: How Fat Am I? Part I

Do you know how your body fat percentage compares to that of your peers?

The term "Body Mass Index" describes a simple method of representing the amount of body fat an individual carries. It was originally developed by a Belgian researcher, Adolphe Quetelet around 1840. It was meant to compare individuals in large populations. It was not intended to be applied in a "guilt-inducing" way to label someone as overweight.

Here's a table so you can look up your BMI for yourself. Click on the chart to see it in a larger size, then click the back arrow to return to this page:


Is the BMI calculation rocket science? No, it's not rocket science, you can estimate your body mass index (as shown on the charts) with elementary arithmetic as taught in Excel Math.

First, measure your weight and height, then proceed to the calculations.

CALCULATIONS
We'll do this in both standard and metric units. First the standard US units:
Weight   185 pounds
Find your height in inches
Height   69 inches
Now multiply weight by 703 x 185 = 130,055
Now multiply height by itself  (height squared) 69 x 69 = 4761
Divide weight by the height squared   130,055 ÷ 4761 = BMI 27.3

To do the same calculations in metric units, start with kilograms (or divide pounds by 2.2):
Weight 84.1 kg
Then find your height in meters (or multiply inches x .0254)
Height 1.753 m
Now multiply height by itself (height squared) 1.75 x 1.75 = 3.073
Now divide weight by the height squared     84.1 ÷ 3.1 = BMI 27.1 

CONCLUSIONS
Now do we know our true body fat percentage? NO, we have a guesstimate. Finding real body fat IS rocket science.

Body mass composition is more accurately calculated using hydrostatic density testing - in a laboratory with measurements taken with accuracy of ±.05 cm; using with skin-fold calipers and pinching skin in various specified places, calculation of total body volume by immersing you in a water tank; and tossing bones from a newt into smoldering lotus leaves (optional).

We'll talk about this more tomorrow.