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5 Things You Didn’t Know About Body Mass Index (BMI)

The term Body Mass Index (BMI) is virtually a household term today, given how deeply we’re all interested in our health. Via discussions on my wellness groups, I found some of us don’t know what exactly is BMI and how to relate to it. So, here goes.

What is Body Mass Index / BMI​1​

BMI is the most widely used measure of adiposity (how much fat is in our bodies) and weight status. The formula to measure BMI is:

BMI = Weight in kgs / (Height in meters)2

Which is, your weight in kilos, divided by the square of your height in meters. For example, if you weigh 60 kilos and your height is 5 feet 2 inches or 158.5 centimeters, you would calculate your BMI as follows.

Weight: 60 kgs
Height: 158.5 cm / 100 = 1.585 meters
BMI: 60 / (1.585 x 1.585) = 23.8 kg/m2

Weight StatusBody Mass Index
Normal18.5 – 24.9 kg/m2
Overweight25.0 – 29.9 kg/m2
Obese> 30.0 kg/m2

These BMI standards may not apply to athletes and muscular individuals, as their body mass will largely be composed of muscle and not fat. ​2​

Calculate your BMI using the form below.

50
Select your weight in kilograms
150
Select your height in centimetres

Your Body Mass Index

BMI Co-Relations

Though we associate BMI most commonly with our weight status, BMI also has other associations, some of which are as follows.

  1. Male fertility. ​2​
    1. BMI of 20 – 25 kg/m2 is associated with normal fertility.
    2. BMI of 18 kg/m2 may be too low for desirable outcomes
    3. BMI of 25 – 27 kg/m2 might cause a slight reduction in fertility
    4. BMI of > 27 kg/m2 is co-related with significant reduction in fertility
  2. Lung function.​3​ Studies indicate a strong relationship between BMI and lung function, though the details of the mechanism is yet unknown.
  3. Lung cancer.​4​ There appears to be a connection between low body mass index and the risk of lung cancer. This could be explained due to the connection of cigarette smoking with both, risk of lung cancer and leanness.
  4. Nutritional failure.​5​ A BMI of less than 18.5 kg/m2 is considered to be caused by nutritional failure.
  5. Blood Pressure.​6​ Current BMI is usually the strongest anthropometric predictor of blood pressure, though conditions do exist that contradict this connection.

References

  1. 1.
    Gallagher D, Chung S. Body Composition. In: Encyclopedia of Human Nutrition. Vol 1. 2nd ed. Elsevier ; 2005:2167.
  2. 2.
    Frisch RE. Fertility. In: Encyclopedia of Human Nutrition. Vol 2. 2nd ed. Elsevier Academic Press; 2005:2167.
  3. 3.
    MacDonald A. Lung Diseases. In: Encyclopedia of Human Nutrition. Vol 3. 2nd ed. Elsevier Academic Press; 2005:2167.
  4. 4.
    Alberg AJ, Samet JM. Epidemiology of Lung Cancer. In: Encyclopedia of Human Nutrition. Vol 1. 2nd ed. Elsevier Academic Press; 2005:2167.
  5. 5.
    Dowsett J, Tully O. Cystic Fibrosis. In: Encyclopedia of Human Nutrition. Vol 1. 2nd ed. Elsevier Academic Press; 2005:2167.
  6. 6.
    Adair LS. Non-Fetal. In: Encyclopedia of Human Nutrition. Vol 2. 2nd ed. Elsevier Academic Press; 2005:2167.

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