Body Mass Index (BMI) and Waist Circumference

The information below is an insert from the 'Best Practice Journal' in 2014.

Body mass index (BMI) is the most common way to clinically consider weight in relation to height. This is calculated by dividing the patient’s weight in kilograms by their height in metres squared. Calculating BMI can be a useful entry point for educating patients about the health risks of obesity. Given the increasing prevalence of obesity some patients may not consider themselves to have a weight-related health problem. The risk of morbidity and mortality is lowest for patients who are in the healthy weight range:3

    • < 18.5 kg/m2 – underweight
    • 18.5 – 24.9 kg/m2 – healthy weight
    • 25.0 – 29.9 kg/m2 – overweight
    • ≥ 30.0 kg/m2 – obese*

* Healthy people with a high amount of muscle mass, e.g. athletes, may be classified as obese using BMI cut-offs.

Waist circumference may also be used by health professionals to assess the risk of health complications in adults:3

  • The risk of long-term disease is increased at ≥ 80 cm for females and is high at ≥ 88 cm
  • The risk of long-term disease is increased at ≥ 94 cm for males and is high at ≥ 102 cm

There may be differences in the threshold for risk across populations of different ethnicities for waist circumference.

The health risks of excess weight in children and adolescents are generally assessed using age-related cut-off values because they are continuing to grow.3

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