Are We Setting Our Kids Up To Be Obese? (Part 2 – BMI)

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By: Kerri Yarsley

So what is overweight or obese?

In simple terms, a person is classified as Overweight if they have a Body Mass Index (BMI) equal to or greater than 25. A classification of Obese occurs from a BMI of 30 and there are three levels of obesity:

  • Level 1 – BMI 30 to 34.9
  • Level 2 – BMI 35 to 39.9
  • Level 3 – BMI ≥ 40

How do you work out the BMI?
The Body Mass Index is determined from a person’s weight in kilograms divided by the square of their height in metres (kg/m2).
For those who live in a non-metric system, one pound (lb) is 0.453 kilograms (kg) and one centimetre (1/100 of a metre = 1 cm) is 0.3937 inches, so you can work out the exact BMI for yourself and your child. However, if maths is not your strong point, and you only want a rough idea of your BMI, then I have drawn up the table below to help you determine where you or your child are based upon your weight and height.

The Weight in kgs and lbs is displayed in the first two columns, respectively. The Height in feet and inches (Ft In) and in centimetres (Cm) is displayed in the top two rows, respectively. So when you know your weight and height just find the closest equivalent weight in the left hand column and then look across that row to the right until you find the closest equivalent number corresponding to your height. The number in the box that intersects these two lines is your approximate BMI:

⦁ If the box lies in the BLUE range, then that means you are underweight.
⦁ If the box is in the GREEN range, then you are in the normal range.
⦁ A box in the YELLOW range indicates you are overweight, but not obese.
⦁ A box in the ORANGE range indicates you are in the obese category at level one.
⦁ A box in the RED range indicates you are in the obese category at level two.
⦁ A box in the PURPLE range indicates you are in the obese category at level three.

If you or your child are less than 4’0″ or greater than 6’8″ in height, then you can determine your BMI using one of the following equations:

Metric Equation: BMI = W/H2, where W is weight in kgs and H is height in metres
Non-Metric Equation: BMI = (w x 0.453)/(h/(0.3937 x 100))2, where w is weight in lbs and h is height in inches

Some examples:
Mary weighs 110lb (or 50 kg) and is 5 feet tall. She has a BMI of 21.53 and therefore falls into the Normal range, which is between 18.5 and 24.9. Her cousin Mildred is only 4’6″ tall, but weighs the same as Mary. Mildred’s BMI is 26.58 which pushes her into the Overweight range. Mary’s son Matt is only 14 years old, slim build and still growing. He stands 5’6″ tall and also weighs the same at 50 kg. His BMI is 17.79 which is below the 18.5 threshold and hence, Matt is considered Underweight.

The neighbours down the street are taller than Mary’s family but they also eat a lot of fast foods because they have a busy lifestyle. Susan weighs 155lb and is 5’7″ tall. To convert Susan’s weight and height into metric measurements, we will use the Non-Metric

Equation above:
Susan’s BMI = (155 x 0.453)/(((5×12)+7)/(0.3937 x 100))2
= (70.215)/((60+7)/39.37)2
= 70.215/(67/39.37)2
= 70.215/1.702
= 70.215/2.89
= 24.296 or 24.3 approximately
This indicates that Susan is on the high end of the Normal range. If this person was only 160cm tall, then their BMI would be very different: 70/(1.6×1.6) = 70/2.56 = 27.34 This figure throws them into the Overweight category.

Susan’s husband Mitch weighs 90kg with a height of 5’8″ tall and he enters a further category:
90/(1.727×1.727) = 90/2.983 = 30.171
Mitch is considered to be in the first level of obesity.

OK, enough of the Maths lesson.  Now that you know how to work out the BMI for you and your family, if it’s 25 or above, then you need to seriously look at your lifestyle.

Next time, in Part 3 of this series of articles, I shall delve more into the food that people are eating; those foods that should be avoided; and the foods that we should be feeding our kids for their present and future health.

[author image=”” ]Kerri Yarsley, BSc, DipEd, GradDipCompSc, DipBus is… an author, parent, technical writer, martial artist, vegetarian and humanitarian. She guides you through one of life’s most challenging roles with empathy, compassion, and creativity. [/author]


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