The BMI  is not a direct measure of body fat but it is the most widely investigated and most useful indicator, to date, of health risk associated with under and overweight.

Note: For persons 65 years and older, the 'normal' range may begin slightly above BMI 18.5 and extend into the 'overweight' range. 

To clarify risk for each individual, other factors such as lifestyle habits, fitness level, and presence or absence of other health risk conditions also need to be considered.

Adapted by the Canadian Guidelines for Body Weight Classification in Adults - Quick Reference Tool for Professionals