Body Mass Index (BMI)–Guide
The most recent obesity statistics from the World Health Organization (WHO) make grim reading. The WHO published an updated list of statistics in February 2018 and found that global obesity has tripled since 1975. There are now 1.9 billion overweight adults around the world, 650 million of whom are obese.
The terms ‘overweight’ and ‘obese’ are defined as “abnormal or excessive fat accumulation that may impair health” by the WHO. In other words, aesthetics doesn’t enter the equation; carrying too much weight is bad for your health. There are numerous tools used to calculate whether or not a person is overweight. Even with the advances in medical technology, the Body Mass Index (BMI) is one of the most frequently used measurements of a person’s physical shape and general health, some 150 years after it was first conceived.
What is the Body Mass Index (BMI)
The body mass index, occasionally called the Quetelet index, is a value taken from a person’s height and weight. It is also determined via a BMI chart table and is an attempt to quantify the level of tissue mass (comprised of bone, fat, and muscle) in a person.
The result is used to determine if that individual is obese, overweight, normal weight or underweight depending on where they fall within the BMI category ranges.
How is BMI Calculated?
The body mass index formula is easy to determine. It’s a simple calculation that takes into account your weight and height.
- The imperial BMI formula = Weight (LBS) x 703 ÷ Height (Inches²)
- The metric BMI formula = Weight (KG) ÷ Height (Metres²)
If you wish to calculate your BMI using the imperial system, here’s the height and weight conversion figures:
- 1 kilogram = 2.2 pounds
- 1 foot = 12 inches
- 1 inch = 2.54 centimetres
If you are 5ft 4 inches by the imperial system, you are 162.56cm or 1.63m (rounded up) by the metric system.
Example BMI Calculations
Example 1: This is how to calculate your body mass index score if you were to weigh 209 pounds and are 6 feet 2 inches tall.
- 209 pounds = 95 kilograms
- 6 feet 2 inches = 1.88m
- 1.88 x 1.88 = 3.53
- 95/3.53 = 26.91
The BMI Score in this case = 26.91.
Example 2: Some countries use an entirely different calculation to reach the same result.
Weight in pounds / your height in inches squared x 703
Using the same example as before, you calculate as follows:
- (209 / 74 x 74) x 703 = (209 / 5,476) x 703
The BMI Score in this case = 26.83.
Why the difference? Because there is a certain element of ‘rounding up’ or ‘rounding down’ involved e.g. 26.784 becomes 26.78 and so on.
But where does this place you on the BMI category chart? In the next section we cover the bmi categories and explain the classifications.
Body Mass Index Categories
Technically, the BMI scale will place you in one of six categories. The table below lists the BMI categories along with the BMI score associated with each category.
|Classification||Body Mass Index Score|
|Underweight||less than 18.5|
|Normal Weight||18.5 – 24.9|
|Overweight||25 – 29.9|
|Obesity (Class 1)||30 – 34.9|
|Obesity (Class 2)||35 – 39.9|
|Extreme Obesity (Class 3)||40+|
The following body mass index chart allows you to manually get your BMI score and includes a classification of the BMI category you reside within.
While it is true that there are a few concerns about BMI, it is still the most tried and trusted way to ascertain the average person’s general health. It is one of the quickest and easiest methods of determining whether you need to lose/gain weight and change your lifestyle. We recommend that you find out your BMI as soon as possible and if it is above or below the average range, book an appointment with your physician and seek advice. This simple test could prevent serious health issues going forward.
If your BMI is over 25 or below 18.5, you should conduct a body fat percentage test and also look at your waist-to-hip and waist-to-height ratios. A combination of all these measurements, plus an honest look in the mirror, should help you determine whether you need to lose or gain weight.
What isn’t in doubt is the growing levels of obesity around the world. The average BMI score of dozens of nations is in the overweight category and there are genuine fears that within a generation or two, there will be more obese people than non-obese.
It is a combination of longer working hours, easy access to cheap processed foods, and a lack of desire to exercise that is responsible for the current obesity epidemic. It would behoove nations in Europe, Oceania and North America, to look at the example set by countries in the Far East of Asia such as Japan which has an average BMI of 22.5, almost directly in the center of ‘normal’. Reduced consumption of processed foods and reliance on fresh fish, fruit, and vegetables ensures that Japan is one of the world’s healthiest nations.
For the record, there is unquestionably a link between BMI and wealth globally. Most of the countries with the lowest BMI averages are among the poorest on the planet. They include Bangladesh (20.2), Eritrea (20.2) and Ethiopia (20.3).
Meanwhile, several of the world’s wealthiest countries have the highest BMI averages. They include Kuwait (29.5), USA (28.8), and the United Arab Emirates (28). Unfortunately, when we revisit these statistics in a decade or so, the average BMI of most countries will have increased and at least one will enter the ‘Obese’ zone of 30 as an average.