Overweight and obesity refer to excess body weight, which is a risk factor for many diseases and chronic conditions and is associated with higher rates of death. It mainly occurs because of an imbalance between energy intake (from the diet) and energy expenditure (through physical activities and bodily functions).
Genetic factors, schools, workplaces, homes and neighbourhoods, the media, availability of convenience foods, and portion sizes can all influence a person’s body weight.
Measuring overweight and obesity
Body Mass Index (BMI)
- BMI is an internationally recognised standard for classifying overweight and obesity in adults.
- While BMI does not necessarily reflect body fat distribution or describe the same degree of fatness in different individuals, at a population level BMI, is a practical and useful measure for monitoring overweight and obesity.
- BMI is calculated by dividing a person’s weight in kilograms by the square of their height in metres. A BMI of 25.0–29.9 is classified as overweight but not obese, while a BMI of 30.0 or over is classified as obese. A BMI of greater than 35.0 is classified as severely obese.
- To calculate your BMI and see how it compares with other Australian adults, enter your height and weight into the AIHW BMI calculator.
- Height and body composition are continually changing for children and adolescents, so a separate classification of overweight and obesity (based on age and sex) is used for people aged under 18 (Cole et al. 2000).
- Waist circumference for adults is a good indicator of total body fat and is a better predictor of certain chronic conditions than BMI, such as cardiovascular risk and type 2 diabetes (NHMRC 2013). A waist circumference above 80 cm for women and above 94 cm for men is associated with an increased risk of chronic conditions. A waist circumference above 88 cm for women and above 102 cm for men is associated with a substantially increased risk of chronic conditions (WHO 2000). For information on measuring and understanding your waist circumference, see Heart Foundation.
Children and adolescents
In 2017–18, 1 in 4 (25%) children and adolescents aged 2–17 were overweight or obese (an estimated 1.2 million children and adolescents). Of all children and adolescents aged 2–17, 17% were overweight but not obese, and 8.2% were obese. Rates varied across age groups, but were similar for males and females (ABS 2018a).
In 2017–18, 2 in 3 (67%) Australians aged 18 and over were overweight or obese (36% were overweight but not obese, and 31% were obese). That’s around 12.5 million adults.
Men had higher rates of overweight and obesity than women (75% of men and 60% of women), and higher rates of obesity (33% of men and 30% of women).
Obesity is more common in older age groups – 16% of adults aged 18–24 were obese, compared with 41% of adults aged 65–74.
See Overweight and obesity: an interactive insight for information on age differences in overweight and obesity.
The proportion of adults with a waist circumference associated with a substantially increased risk of chronic conditions was higher in women than men (46% of women and 36% of men). This risk increased with age (peaking at 57% of men aged 65–74, and 65% of women aged 75–84) (ABS 2018a).
Why is the most recent data from 2017–18?
Nationally representative estimates on measured overweight and obesity are derived from the Australian Bureau of Statistics (ABS) National Health Survey (NHS).
Due to the COVID-19 pandemic, physical measurements (including height, weight and waist circumference) were not taken at the time of the NHS 2020–21, the most recent NHS.
While self-reported height and weight were collected as part of the survey, self-reported data underestimates actual levels of overweight or obesity based on objective measurements (ABS 2018b).
As self-reported and measured rates of overweight and obesity should not be directly compared, the figures presented on this page reflect the latest nationally representative data based on measured height, weight and waist circumference.
Children and adolescents
The prevalence of overweight and obesity in children and adolescents aged 5–17 rose from 20% in 1995 to 25% in 2007–08, then remained relatively stable to 2017–18 (25%) (Figure 1).
Similarly, the prevalence of obesity increased from 4.9% in 1995 to 7.5% in 2007–08 then remained relatively stable to 2017–18 (8.1%). Rates of overweight but not obese children and adolescents increased between 1995 and 2014–15 (from 15% to 20%), then declined to 17% in 2017–18 (ABS 2013a, 2015, 2019; AIHW analysis of ABS 2009, 2013b).
See Overweight and obesity among Australian children and adolescents for more information.