What is the meaning of Body Mass Index (BMI)?
 The Body Mass Index is used to determine if someone is underweight, overweight or if they are an ideal weight for their height.
BMI is a mathematical formula that calculates your ‘weight to height ratio’. Although the BMI range is not an exact range of healthy and unhealthy weight, it is a useful guideline for gauging your ideal weight for your height. A BMI of 25 to 29.9 indicates a person is overweight, but not at high risk of developing serious health problems. A person with a BMI of 30 or higher is considered obese; and is able to seek medical treatment to improve their health.
How is BMI calculated?
BMI is calculated by taking your height in metres (example: 5 feet 6 inches is approx. 1.67 metres) then multiplying it by itself to get metres squared (1.67 x 1.67 = 2.81). Then take your weight in kilograms (example: 11 stone 4 pounds is approx. 72kg), divide it by your height squared number to get the result (example: 72 / 2.81 = 25.6).
The BMI in this example is 25.6, which indicates that 11 stone 4 pounds is close to the correct weight for a height of 5 feet 6 inches. The table below shows you how BMI results are to be interpreted:
| World Health Organisation classification |
BMI |
Risk of co-morbidities (Serious health issues associated with obesity) |
| Underweight |
18.5 or below |
Low (but risk of other problems) |
| Normal range |
18.5 to 24.9 |
Average |
| Overweight |
25.0 to 29.9 |
Mildly increased |
| Obese |
30.0 to 30.9 |
Obese |
| Class I |
31.0 to 34.9 |
Moderate obesity |
| Class II |
35.0 to 39.9 |
Severe obesity |
| Class III |
40.0 and above |
Very severe obesity |
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