The Body Mass Index (BMI) is a calculation that takes a person’s height and weight into account natural variations in body shape, giving a healthy weight range for a particular height to work out if the weight is healthy.
The BMI calculation divides the weight in kilograms divided by the square of height in meters squared. For example, A BMI of 25 means 25kg/m2.
For most people, BMI provides a reasonable estimate of body fat and can be an indicator of high body fatness and used to screen for weight categories that may lead to health problems, but it is not diagnostic of the body fatness or health of an individual.
For most adults, an ideal BMI is in the 18.5 to 24.9 range. For children and young people aged 2 to 18, the BMI calculation takes into account age and gender as well as height and weight.
If the BMI is below 18.5 is considered as in the underweight range. Between 18.5 and 24.9 means healthy weight range. Between 25 and 29.9 is already in the overweight range. Between 30 and 39.9 is in the obese range. However, BMI does have some limitations. BMI of greater than 40 is called as morbid obesity.
As well as measuring BMI, healthcare professionals may take other factors into account when assessing a healthy weight. Factors such as age, sex, ethnicity, and muscle mass can influence the relationship between BMI and body fat. Also, BMI doesn’t distinguish between excess fat, muscle, or bone mass, nor does it provide any indication of the distribution of fat among individuals.
Muscle is much denser than fat, so very muscular people, such as heavyweight boxers, weight trainers and athletes, may be a healthy weight even though their BMI is classed as obese.
Ethnic group can also affect the risk of some health conditions. For example, adults of Asian origin may have a higher risk of health problems at BMI levels below 25.
We should not use BMI as a measure during pregnancy.
Despite these limitations, BMI continues to be widely used as an indicator of excess weight. BMI of greater than 35 will caused serious medical problems.