How to calculate BMI ?

In Curious questions, Human body, Life Science
Namita Jain
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Your body needs a reasonable quantity of fat in it to stay healthy. However, if this quantity of fat in body dips too low or zooms too high, it can lead to health problems of various kinds. Therefore maintaining just the right amount of body fat is an essential part of self health care. There

Your body needs a reasonable quantity of fat in it to stay healthy. However, if this quantity of fat in body dips too low or zooms too high, it can lead to health problems of various kinds. Therefore maintaining just the right amount of body fat is an essential part of self health care. There are several ways of calculating the amount of body fat. Many of these methods are complicated and may require specialist machines or expert guidance.

On the other hand, BMI or body mass index is an accepted and easy method for estimating a person’s fat levels or ‘fatness’. BMI is calculated using a person’s height in meters and weight in kilograms. BMI is a reasonably reliable way of finding out a person’s possible health risks as per his or her weight status category.

BMI formula

If you have studied fractions and squaring of numbers in school, you can calculate BMI easily using a pen and paper too. The basic BMI formula is:

BMI= Weight in kilograms/ (height in meters)2

Do remember that while BMI calculation is not difficult, the relevance of BMI numbers for kids is different from that of adults. This is so because unlike adults, children and teens keep growing in height and their body fat keeps changing alongside. Plus girls and boys can have different BMI criteria.

BMI calculator

For the reason mentioned above, BMI calculators for adults (>18 years) are different from BMI calculators for kids (2-18 years).There are several sites that offer BMI calculators for both categories.

BMI calculator for adult men and women

BMI calculator for adult males and females requires height and weight numbers. Once you have calculated the number, you can check the associated weight status categories as per BMI to gauge relevant health risks:

Under 18.5 – Underweight
18.5-24.9 – Healthy weight range
25.0- 29.9 – Overweight
Above 30 – Obese

For adults, BMI in the range of 18.5 and 24.9 is an indicator of optimal body fat. Any number beyond this range, whether high or low, is a health alert that should be heeded at the earliest.

BMI calculator for kids

As mentioned above, BMI for children is age and gender specific. In other words, BMI numbers depends on whether you are a boy or a girl and how old you are. So when you use a BMI calculator for kids, you also have to specify age and gender along with height and weight.
As per their BMI number, children can be underweight, healthy weight, overweight and obese. As is obvious, it is best to belong to the healthy weight category.

How accurate is BMI

BMI is reasonably reliable but it may not be very accurate in following instances:

For sportspersons/ athletes- Physically super active people have a lot of muscle bulk instead of fat. Their BMI is relatively high yet they are healthy.
BMI parameters can differ as per race (Europeans, Asians and Africans can have different degrees of health risks for the same BMI number).

What do BMI numbers indicate

If BMI is very low, it means either you are not taking in enough nutrition or your body is not able to digest and absorb nutrition well. Many a times, those addicted to drugs, alcohol or tobacco too suffer from low BMIs. Eating disorders like anorexia and bulimia too can lead to very low BMIs. Low BMI can cause ailments like weak bones and muscles, heart abnormalities, anemia, low immunity and infertility (not being able to bear children). It may sound surprising but having a too low BMI number is far riskier than being in the overweight category.

On the other hand, if BMI is excessive, diseases like diabetes, heart disease, high blood pressure and osteoarthritis are waiting to happen. The higher the BMI, the higher the risks for these lifestyle diseases.

Either way, you need to get back to the healthy BMI zone. Some common sense ways of managing BMI are to amend an unhealthy lifestyle, eat a nutritious diet with the right amount of calories and lead a physically active life, However if the BMI is too high or too low, it is best to consult a trained health care professional for treatment at the earliest.