Measuring Youths’ Body Mass Index (BMI) Score

I used to tell my students if they wanted to find out if they were too fat they should run in place in front of a full length without clothing. If something jiggled, and it wasn’t supposed to they could conclude that what was moving was fat.

It brought laughs from the students, since they all understood—fat in excess is noticeable, no matter how effective one is in denying reality. As teachers/youth leaders this technique is not recommended for obvious reasons.

A few weeks ago I summarized, in dictionary format, the many ways in which fat can be measured. Here and in subsequent blogs I will flesh (excuse the pun) out several more common techniques.

Body Mass Index (BMI) – BMI is a number calculated from a person’s height and weight. Advocates say it provides a reliable indicator of body fatness for most people. Additionally, the BMI helps screen for weight categories that lead to health problems such as Metabolic Disease Syndrome (Obesity, Type 2 Diabetes and Vascular Disease).

Detractors, however, facetiously call it the “baloney mass index” since it under reports the number of people who are obese (Baverman, E. et. al. American Association of Clinical Endocrinologists Meeting AACE, 2010; Abstract 609).

On the other hand, epidemiologists and classroom teachers like the BMI because it provides a rough estimate of what is going on in the population being examined (classroom or community). But care must be exercised since it misses people who seem to be overweight or obese because of a high BMI score yet they are carry a great deal muscle and bone (lean body) tissue.

A good example is a football player who may be 5’7” tall and weigh 208 pounds. His BMI will be well over 30 (way beyond the recommended level) but he has a 32” waist, 46” chest, muscular arms and legs. By the same token you can have an average sedentary man weigh the same, at the same height and his waist is 46” and his chest 38”. His arms and legs tend to be flabby. In other words he is carrying more of his weight as fat and the football player is not.

The Centers for Disease Control and Prevention have a site to help you calculate adult and youth BMIs. Just go to:

If you prefer, you may estimate a child’s BMI by using this formula:
Child’s Weight (in lbs.) x 704.5 divided by Height (in inches) x Height (in inches)
Example (100 lbs) x (704.5) divided by (50 inches) x (50 inches) is:

(100) x (704.5) = 70,450
(50) X (50) = 2,500
70,450 divided by 2,500 = 28.18

If you don’t like doing the math, look at the Table below
1. Find height in inches on the far left, let’s say 50 inches.
2. Find weight inside the box, let’s say 100 pounds.
3. Where the weight and height intersect, use your forefinger and move to the top of the Table.
4. There you will find your BMI Score. In this instance 28.

Rich: Maybe show this illustration with a pen mark

TABLE – Body Mass Index Table for children

Once the BMI score is determined go to the chart below to see if your youth is in the healthy range or not.

CHART – Healthy BMI Scores

AGE Boys Girls
5 20-15 21-16
6 20-15 21-16
7 20-15 22-16
8 20-15 22-16
9 20-14 23-14
10 21-14 23-14
11 21-14 24-14
12 22-15 24-14

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