Body Mass Index (BMI), a measurement of obesity

Body Mass Index (BMI), a measurement of obesity

We have learnt how to measure almost anything: from the mass of the sun to the diameter of an electron, from per capita income to geographic locations with pinpoint accuracy, from atmospheric pressure to capacity of your hard drive. But can we measure obesity? Of course we can. Body Mass Index (BMI) is the measurement of obesity devised by Adolphe Quetelet. Obesity measurement doesn’t only depend on the body mass, the height is also an important parameter. Meaning that we can call Jack fitter than Cooper, even though Jack weighs more, because Jack is substantially taller than Cooper. BMI takes both body mass and body height into consideration and is defined as the body mass divided by the square of the body height. It is expressed in units of kg-per-meter-square. Mass is measured in kilograms and height is measured in meters.

BMI is used to classify a person into different levels of obesity, commonly underweight, normal weight, overweight, obese. If you have a BMI less than 18.5, you are suffering from underweight. You are normal with a BMI from 18.5 to 25, but have overweight with BMI from 25 to 30. And with a BMI of over 30, you are seriously obese. This was the common classification. There are variations among countries. For example, in Hong Kong, normal weight ranges from 18.5 to 23. The Japanese will call you obese, if you have BMI greater than 25. There are even different classification for children. To give you one interesting trivia, in order to fight anorexia, France, Israel, Italy and Spain have banned fashion models having a BMI below 18 in ramp shows.

However, there are debate on BMI. Many other factors, rather than body mass and height can be considered to define what we generally call obesity. BMI ignores, for example, the variation in physical characteristics. BMI may suggest that a man of 5 feet 10 inch (1.78 meter) is normal with 165 pounds (75 kg), but if he has a slender body structure, he may be classified into the overweight class with 165 pounds. On the contrary, someone of the same height but larger body structure can be considered okay even with 180 pounds (82 kg). So, sometimes common sense should also be applied in measurement of someone’s ideal weight. BMI is not sufficient to differentiate between muscle mass and fat mass. A muscular, tough, eight pack body builder can be obese in the eyes of BMI. Alternatives of BMI include BMI prime, waist circumference, surface-based body shape index, modified body mass index.

According to 2014 data by WHO on mean BMI, Nauru, Cook Islands, and Niue top the list among other countries with overall mean BMI 32.5, 32.3, 32.3 respectively. USA ranked 19 with 28.8 after Bahamas. It is time, we targeted for a low BMI through a healthy lifestyle. For that purpose, home gym courses are suggested if you don’t know what to do, how to do.

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