Body Mass Index
A convenient way for an adult to assess whether his or her weight is in the healthy range is by using the Body Mass Index. BMI is calculated by dividing weight in kilograms by height in metres squared.
BMI = Weight (Kg)/Height2 (Metres2)
For example, a woman 1.67m in height and weighing 65kg would have a BMI of 23.3
BMI = 65/1.672
BMI = 23.3
This BMI falls within the healthy weight range.
Overweight is measured as 25 or more with obesity determined as 30 or more.
However there are exceptions to this rule, BMI calculations can overestimate the amount of body fat for:
- Body builders
- Some high performance athletes or defence personnel
- Pregnant women
BMI calculations can underestimate the amount of body fat for:
- The elderly
- People with a physical disability who are unable to walk and may have muscle wasting
BMI is also not an accurate indicator for people with eating disorders like anorexia nervosa or people with extreme obesity.
Therefore the BMI is not the best measure of fatness or health risk. Increasingly experts believe that the type of fat and where it is on your body may be more important than BMI – and that your waist circumference is really the figure that you should pay attention to. If you have a waist measurement above 94cm for men and 80cm for women you may be at risk of serious chronic disease.
More information about BMI can be found on the Healthy Weight web site.