Diagnosis
The diagnosis of obesity is usually based on a physical examination and a patient history (i.e., eating and exercise habits).
A measurement called the body mass index (BMI) does not directly measure body fat, but it is a useful tool to assess the health risk associated with being overweight or obese. A BMI of 18.5 to 24.9 is considered within the healthy range. The BMI is calculated using kilograms (kg) and metres (m) instead of pounds (lb) and inches/feet. Keep in mind that 1 lb equals 0.45 kg and 1 inch equals 0.0254 m.
BMI is calculated as follows:
BMI = body weight (kg) ÷ height² (m)
Example: if you weigh 150 lbs (68 kg) and are 5’8″ (1.73 m) tall, divide 68 by (1.73 × 1.73), or 2.99. The result is 22.74, which is right in the middle of the healthy range.
Health Canada classifies BMI according to the associated risk of developing health problems:
| - BMI value | - Classification* | - Health risk |
| Less than 18.5 | Underweight | Increased |
| 18.5 to 24.9 | Normal weight | Least |
| 25.0 to 29.9 | Overweight | Increased |
| 30.0 to 34.9 | Obese class I | High |
| 35.0 to 39.9 | Obese class II | Very high |
| 40 or higher | Obese class III | Extremely high |
Calculate your BMI here:
*The above classification does not apply to people younger than 18 years of age, pregnant women, or breast-feeding women. For people 65 years and older, the “normal” range is higher, beginning slightly above 18.5 and extending into the “overweight” range.
