BMI as a Measure of Your Health Index:

The What, the When, Its Strengths and Its Weaknesses

The What: What does BMI stand for?

BMI stands for body mass index. It’s actually a rough estimate of how obese you are. Currently, it continues to remain the most widely utilised assessment tool in the evaluation of obesity risk. Sadly, the present BMI standards don’t take into account other important measurements such as waist-to-hip ratio, skinfold thickness and waist circumference

Also, there is much variation in BMI among different ethnicities, age and gender. What may be perceived as a normal weight for the average Kiwi (Caucasian) may not be seen as a normal weight for an average Japanese (Asian).The establishment of certain standards when it comes to different populations will help tremendously in evaluating obesity risk.

Formula to Work Out BMI

As you can see, the data needed to calculate your BMI is your height and weight. Also included in the infographic is an example for a person who weighs 90kg with a height of 1.8m. This person has a calculated BMI of 27.8, so what does this mean?

You can use this table to determine whether your BMI puts you in the underweight, normal or overweight category:

BMI	Weight Status
Below 18.5	Underweight
18.5-24.9	Normal
25.0-29.9	Overweight
30.0 and Above	Obese
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The World Health Organization (WHO) uses this to determine if a person is healthy based on their current weight. Being underweight could mean a person is malnourished, suffering from an eating disorder or a significant health condition.

At the other end of the spectrum, are the overweight and obese categories. Though surgeons and other healthcare professionals now use additional categories such as “severe obesity”, “morbid obesity” and “super obesity” for those who are severely overweight. Talk about the next generation of names for upcoming superheroes who were left in the lolly store too long. Another, easier way for some, to determine your BMI is the below chart:

BMI chart

How to use the chart: Look for your weight at the bottom of the chart. Draw a line (imaginary only my friend) from there vertically towards the coloured areas. Intersect that with your height on the left. There you go.

The When: Short (but Stout) History of BMI with Updates on Obesity in New Zealand

Ever wonder who came up with BMI? Or who first used it? Here is a quick rundown of the events leading to BMI becoming the superstar health index:

Adolphe Quetelet, a Belgian statistician, was actually the one who first came up with BMI. He called his formula the Quetelet Formula of Obesity (Not really subtle about what it’s for, huh?). It wasn’t really that accurate because he used different systems of measurement for weight (kilograms) and height (inches). How ironic.
During the disco era (late 1960s to early 1970s), healthcare practitioners used separate tables for males and females to determine if a person is overweight. The tables were called weight-for-height tables. They were very limited because they were only based on your weight.
At around the same time that you were watching Gliding On on TV (1981 to 1985), BMI became an international standard for measuring obesity.
The majority of the public learned about BMI in the 1990s. Almost everyone concerned with health and fitness used it to assess the status of their health.
At the beginning of the year 2000, almost all doctors directly concerned with patient care included BMI as part of their complete assessment for body size and overall health.
The sad thing is that the rate of obesity continues to increase throughout the world. Here are statistics from OECD June 2014:
Japan and Chile have their own nation’s set of BMI normal and abnormal values. As for Kiwis…they’re still working on it.
Today, questions are being raised regarding BMI’s capability as a standard for measuring how healthy you are. Read onwards and see its strengths and weaknesses.

The Mighty BMI: Its Strengths

Calculating your BMI is simple, safe and easy to do.
There are well recognised and accepted limits for what constitutes overweight and obese.
It correlates well with your body fat levels. Though is is best verified by more accurate methods.
It also correlates well with your chances of developing chronic metabolic diseases. For example, a high BMI translates to a greater risk of developing type II diabetes mellitus or dying earlier.
It’s inexpensive.
It’s a non-invasive procedure. No fat grabbing and poking with an instrument, unlike the skinfold test.

The Inadequate BMI: Its Weaknesses

BMI can’t distinguish fat from muscle. Imagine spending countless hours and days pounding iron at the gym and this simple assessment tool can’t even distinguish whether what you’ve gained is muscle or fat. Bodybuilders and strength training athletes must certainly hate this.
BMI is blind to age. So its not that suitable for measuring body fat among the elderly and children. For example when elderly and young people with similar BMI were compared, the elderly had a larger percentage of their weight as fat. Likewise, BMI is not helpful for children under 2 years of age.
BMI is also blind and deaf to your race or gender. Normal muscle and bone mass levels can vary greatly among different ethnic groups. For example Polynesians have a low fat mass to lean mass proportion compared with Europeans. Also, Asians may be at risk of developing metabolic diseases at a lower BMI level than other ethnic groups.
BMI doesn’t take into account where the excess weight is deposited. A pregnant woman can’t use BMI to assess how healthy she is. The weight she has gained is around her belly, her unborn baby.
Excess fat may be deposited around your internal organs (visceral fat) and you may still look fit. BMI will not know that either and tell you that you’re overweight even if you look fit. Though visceral fat is even more dangerous to your health than subcutaneous fat. Click here to read more.

The Practical Verdict

For now, BMI is still a useful assessment tool to determine if you’re overweight or underweight. When you deviate from the normal range, either underweight or overweight, there are inherent risks to your health which are easily preventable. Just be sure to keep the limitations of BMI in mind and use other assessment tools where BMI may not be giving the full picture. After all it's better to take action early and prevent metabolic disease from developing altogether.