What is overweight and obesity

Overweight and obesity refers to excess body weight. Excess weight, especially obesity, is a major risk factor for cardiovascular disease, Type 2 diabetes, high blood pressure, sleep apnoea, psychological issues, some musculoskeletal conditions and some cancers. Being overweight can hamper the ability to control or manage chronic disorders, and people who are overweight or obese have higher rates of death.

In 2015, 8.4% of the total burden of disease in Australia was due to overweight and obesity (AIHW 2019). Overweight and obesity was the leading risk factor contributing to non-fatal burden (living with disease) (see Burden of disease).

Collecting information on overweight and obesity is important for managing associated health problems.

Body mass index (BMI)

Body Mass Index (BMI) is an internationally recognised standard for classifying overweight and obesity in adults. BMI is calculated by dividing a person’s weight in kilograms by the square of their height in metres. BMI does not necessarily reflect body fat distribution or describe the same degree of fatness in different individuals. At a population level however, BMI is a practical and useful measure for identifying overweight and obesity.

BMI (kg/m2)


Less than 18.5


18.5 to less than 25

Normal weight range

25 to less than 30


30 or more


Source: World Health Organization (WHO) 2000. Obesity: preventing and managing the global epidemic. Report of a WHO consultation. WHO technical report series 894. Geneva: WHO.

Waist circumference

Waist circumference is an alternative way to assess risk of developing obesity-related chronic diseases. A higher waist measurement is associated with an increased risk of chronic disease. The risk levels presented below are for Caucasian men; and both Caucasian and Asian women.


Increased risk

Substantially increased risk


94 cm

102 cm


80 cm

88 cm

Source: National Health and Medical Research Council (NHMRC) 2013. Clinical Practice Guidelines for the Management of Overweight and Obesity in Adults. Canberra: NHMRC.

For information on how to correctly measure your waist, visit the National Heart Foundation website.

Measuring overweight and obesity in children

Height and body composition are continually changing for children and adolescents. A separate classification of overweight and obesity for children is used based on age and sex (Cole et al. 2000).


AIHW 2019. Australian Burden of Disease Study:  impact and causes of illness and death in Australia 2015, Australian Burden of Disease series no. 19. Cat. no. BOD 22. Canberra: AIHW.

Cole TJ, Bellizzi MC, Flegal KM & Dietz WH 2000. Establishing a standard definition for child overweight and obesity worldwide: international survey. BMJ 320:1240–3.

NHMRC (National Health and Medical Research Council) 2013. Clinical practice guidelines for the management of overweight and obesity in adults, adolescents and children in Australia. Melbourne: NHMRC.