Overweight and obesity refers to excess body weight. People who are overweight or obese have higher rates of death and illness than people of healthy weight, particularly from cardiovascular disease, type 2 diabetes, some musculoskeletal conditions and some cancers.

The main factors influencing overweight and obesity are poor diet and inadequate physical activity. Increased energy intake from the diet without an increase in energy expenditure through physical activity will result in energy storage as fat and weight gain.

Rates of overweight and obesity are continuing to rise in Australia. Collecting information on these trends is important for managing the associated health problems. The AIHW regularly reports on overweight and obesity as a risk factor for chronic disease. Better data are needed to monitor trends in overweight and obesity among particular groups over time, especially children.

Overweight and obesity can be measured in a number of ways, including the commonly used body mass index (BMI). BMI is an internationally recognised measure of overweight and obesity at a population level for both adults and children [1, 2]. You can quickly check whether your weight is in a healthy range by calculating your BMI. The following standard cut-off points are used for people aged 18 and over:

  • underweight BMI <18.5
  • healthy weight BMI ≥18.5 and BMI <25
  • overweight but not obese BMI ≥25 and BMI <30
  • obese BMI ≥30.


BMI Calculator

The Body Mass Index (BMI) is an internationally recognised standard for classifying overweight and obesity in adults. BMI is calculated by dividing the weight in kilograms by the square of the height in metres.

To find out your BMI, enter your details below and click 'What is my BMI?'.

I am cm tall, and weigh kg.

My BMI is , which is considered .

  • 0.0 – 18.4
  • 18.5 – 24.9
  • 25.0 – 29.9
  • 30.0 – 40+

These classifications may not be suitable for all ethnic groups or for children and adolescents. Because BMI changes substantially with age, and can differ for boys and girls, children and adolescents have different cut-off points based on age and sex [1, 2].

Excess body weight can also be measured using waist circumference. A higher waist measurement is associated with an increased risk of chronic disease. According to the World Health Organization guidelines for assessment of risk using waist circumference, Caucasian men and women with a waist circumference of greater than or equal to 94cm and 80cm, respectively, are at increased risk of chronic disease [3].


  1. WHO (World Health Organization) 2000. Obesity: preventing and managing the global epidemic. Report of a WHO consultation. Geneva: WHO.
  2. 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.
  3. WHO 2008. Waist circumference and waist–hip ratio. Report of a WHO expert consultation. Geneva: WHO