About BMI and Obesity
How is Obesity Measured?
Obesity is when excess body fat has accumulated to an extent that a person's health is adversely affected (Word Health Organization). Obesity is measured by calculating your Body Mass Index (BMI). This is a quick way of working out whether you are at a healthy weight for your height.
Your BMI can be calculated by using a formula using weight (in kilograms) divided by your height (in metres) squared, and is expressed as kg/m2.
If you want to find out what your BMI is click here.
Why is the BMI Useful?
The BMI is the best way to classify obesity because, as your BMI increases, so too does your risk of developing weight-related diseases such as non-insulin dependent diabetes, some forms of cancer and as well as your overall increased risk of dying prematurely.
Waist circumference can also be useful as there is some evidence that abdominal obesity is associated with a higher risk of illnesses such as heart disease.
Classification of Obesity Severity
| BMI (kg/m2) | Category | Risk of illness and early death | 18 - 25 | Normal | Normal |
| 25 - 30 | Overweight | Mildly increased |
| 30 - 35 | Class 1 obesity | Moderately raised |
| 35 - 40 | Class 2 obesity | Severely raised |
| > 40 | Class 3 obesity | Very severely raised |
