Research has found a strong correlation between a BMI of 25 and above and the risk of developing diseases such as cardiovascular disease and cancer.
BMI is calculated by dividing a person's weight (kg) by height (m) squared.
The BMI cut offs are:
- Less than 20 - Underweight
- Over 20 to 25 - Desirable or healthy range
- Over 25 to 30 - Overweight
- Over 30 to 35 - Obese (Class I)
- Over 35 to 40 - Obese (Class II)
- Over 40 - Morbidly or severely Obese (Class III)
BMI is only an appropriate measure for 'normal' individuals. It is not appropriate for pregnant women, for use in some medical conditions, the elderly or with children. For measuring obesity in children, special charts have been developed which take into account growth, gender and age.
BMI is also inappropriate for athletes, as the body mass index does not distinguish between fat and muscle mass. Physically fit individuals may be mistakenly classified as being overweight, as they have more muscle mass than body fat.
BMI may not be appropriate for some ethnic groups. For example, a BMI over 27.5 in an Asian person has been estimated by the World Health Organisation to carry the same health risk as a BMI of 30 in a white Caucasian person.
