The body mass index (BMI) is a figure used by physicians and scientists to describe a person’s weight status. The formula used to calculate the BMI takes into account both weight and height. Thus, it gives a more accurate perspective of a person’s weight status than using weight alone.
According to the BMI score, a person’s weight status can be classified as:
- underweight (BMI < 18.5)
- normal (BMI 18.5 – 24.9)
- overweight (BMI 25 – 29.9)
- obese (BMI 30 – 39.9)
- extremely obese (BMI 40 or above)
The body mass index equals a person’s weight divided by the square of their height.
In other words:
BMI = Weight / Height2 (in kg/m2), or
BMI = Weight / Height2 (in lbs/in2) x 703
The BMI score is valid for both men and women, with the following limitations:
- It may overestimate body fat in athletes and other individuals with a muscular build.
- It may underestimate body fat in older people and other individuals with decreased muscle mass.
The body mass index is closely related to a person’s risk of cardiovascular disease. See the cardiovascular risk table for illustration.
Additionally, a person’s cardiovascular risk appears to increase proportionally to the amount of fat deposited around the midsection (which is measured by the waist size). Thus, a waist size greater than 40 inches (in men) and 35 inches(in women) places a person at higher cardiovascular risk, as shown in the cardiovascular risk table.