Body Mass Index (BMI)


Understanding Body Mass Index In Health

 Body Mass index popularly known as BMI is a measurement used clinically to account for an individual’s proportion. It is a ratio of weight in kilograms to height in meter square (Kg/m2).

 It is popularly used to know if an individual is underweight or overweight. At population level, it is used as a standard for indicating morbidity (disease risk) and mortality (death risk). Being underweight can be as a result of underlying illnesses or even having a mental breakdown while being overweight or obese can lead to several health complications like cardiovascular diseases, type 2 diabetes. We find in our society today that being overweight is more common than being underweight and obesity is a problem that needs tackling by overcoming a sedentary lifestyle and choosing to live healthy. Although, Body Mass Index is not an accurate measurement due to the differences in population. Body mass index measurement used for adults will not apply to children and adolescents especially those experiencing puberty because of the growth spurt they experience at this period. Also, males tend to have more weight than their corresponding females in height due to the density of their bones. Although, in terms of body fat, females have more fat than males hence BMI will overestimate the percentage of body fat in such cases. Body mass index will also differ in varying ethnicity for example Indians and Asians have a higher body mass index than Europeans whose body mass index is higher than that of Africans. Body mass index will also overestimate the body fat content for bodybuilders because it cannot differentiate between muscle mass and fat mass, pregnant women, and athletes. Body mass index will underestimate the body fat for elderly individuals (body fat percentage for the elderly can also be overestimated) and for physically challenged individuals.


Body Mass Index in Relation to Healthy Living

It classifies individual weight into four classes; underweight, normal weight, overweight and obese. If an individual is underweight, overweight, or obese, it could be as a result of an underlying disease, malnourishment or simply living a sedentary life. Achieving and maintaining a healthy weight is important for adequate body function and quality immune function, it includes eating healthy, physical activity, optimal sleep and stress reduction. Eating healthy involves eating foods rich in nutrients and cutting out pure carbs and fatty foods. Dieting may promise fast results but dieting limits your nutrient intake, can be unhealthy, and tend to fail on the long run. Physical activity could be simple, for example; evening walks, avoiding too much screen time, especially children. Outdoor activities should be encouraged. Also, the amount of physical activity will depend on your goal, whether to shed weight or to maintain your weight. For those who are underweight, rigorous physical activity is not advised until recovery from nutrient-rich meal therapy proves effective.

Managing weight contributes to good health and as one ages people who have obesity compared to those who are of normal weight are at increased risk for many serious diseases and health conditions. The importance of body mass index even with its limitation cannot be overlooked in clinical practices, it is the go-to for body mass measurements.

How to Calculate your BMI

The two measurements needed for BMI calculation are your weight in kilograms and height in meters.
The weight measurement is divided by the square of the height measurement in meters. 
Safina weighs 65kg and is 1.58 meters tall, what is her BMI? 

First, we square Safina's height 
(1.58 x 1.58 = 2.4964)
Then we divide her weight by the resultant value
65/2.4964 = 26.04 Kg/m2

How can we tell if Safina is Underweight, normal, overweight, or Obese?

Safina is overweight with a BMI value of 26.04

Limitations to BMI

Body Mass Index (BMI) is a measurement that cannot differentiate the state of a person. The limitations of BMI are 
  • Differences in age
  • Pregnancy
  • Ethnic variations
  • Bodybuilders and Athletes
  • Environment factors (urban or rural settlements)
Research suggests that other anthropometric measurements such as skin fold thicknesses, bioelectrical impedance, underwater weighing and Dual Energy X-ray Absorption (DEXA) may be more accurate than BMI. However, the advantages of BMI outweigh the disadvantages hence the limitations are ignored since BMI is easy and cheap to perform it is accepted worldwide.