While BMI can be a quick guide to assessing your weight, it
does have some limitations. It doesn't apply to athletes whose
muscle mass, which weighs more than fat, may put them in
the 'overweight' or 'obese' category.
Similarly, as you get older, BMI may underestimate your risk of
being overweight because a greater proportion of your body
will be fatty tissue rather than muscle.
It also doesn't apply if you're pregnant and you should seek a
doctor's advice if you're worried about your weight during
pregnancy.
However, it is a helpful tool alongside waist measurement
to help you figure out if you would benefit from doing something
about your weight.