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 young people aged under 18 (Cole et al. 2000).

Waist circumference

  • Waist circumference is another common measure of overweight and obesity in adults. A waist circumference above 80 cm for women and 88 cm for men is associated with an increased risk of chronic disease. For information on measuring and understanding your waist circumference, see Heart Foundation.

How common is overweight and obesity?

Children and adolescents

In 2017–18, an estimated 1 in 4 (25%) children and adolescents aged 2–17 were overweight or obese (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 2018).

Adults

In 2017–18, an estimated 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.

More men than women were overweight but not obese (42% of men and 30% of women), but obesity rates for men and women were similar (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 metabolic complications increased with age, and was higher in women than men (peaking at 57% of men aged 65–74, and 65% of women aged 75–84) (ABS 2018).

Trends in overweight and obesity

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 in this age group increased from 4.9% in 1995 to 7.5% in 2007–08 then remained relatively stable to 2017–18 (8.1%) (ABS 2009, 2013a, 2013b, 2015, 2019).

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. This decline did not result in a lower proportion of overweight and obese children overall, but instead resulted in some children moving from the overweight to the obese category.
 

This graph shows the prevalence over time of overweight and obesity in children and adolescents. Three lines indicate the proportions for total overweight or obese, overweight but not obese, and obese across 5 time points (1995, 2007–08, 2011–12, 2014–15 and 2017–18). The graph shows an increase in overweight and obesity from 1995 (20%) to 2007–08 (25%), followed by a stabilisation to 2017–18 (25%).

Adults

After adjusting for different population age structures over time, the prevalence of overweight and obesity among Australians aged 18 and over increased from 57% in 1995 to 67% in 2017–18. This was largely due to an increase in obesity rates, from 1 in 5 (19%) in 1995 to 1 in 3 (31%) in 2017–18.

The distribution of BMI in adults shifted towards higher BMIs from 1995 to 2017–18, due to an increase in obesity in the population over time (Figure 2).
 

This graph shows the changing distribution of BMI over time in adults aged 18 and over. It shows a shift to the right in BMI distribution between 1995 and 2017–18. In 1995, more adults had a BMI in the normal or overweight range compared with adults in 2017–18. However, in 2017–18, more adults were in the obese weight range compared with adults in 1995.

Health impact

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

Overweight and obesity increases the likelihood of developing many chronic conditions, such as cardiovascular disease, asthma, back problems, chronic kidney disease, dementia, diabetes, and some cancers (AIHW 2017). It is also associated with a higher death rate when looking at all causes of death (di Angelantonio et al. 2016).

Variation between population groups

See Health risk factors among Indigenous Australians for information on overweight and obesity among Aboriginal and Torres Strait Islander Australians.

Remoteness area

Overweight and obesity rates differ across remoteness areas, with the lowest rates in Major cities.

In 2017–18, a higher proportion of Australian children and adolescents aged 2–17 living in Inner regional areas were overweight or obese, compared with those living in Major cities (29% and 23% respectively). For children and adolescents living in Outer regional and remote areas, the proportion was 27% (ABS 2019).

For Australians aged 18 and over, 70% of adults living in Outer regional and remote areas and 71% in Inner regional areas were overweight or obese, compared with 65% in Major cities (after adjusting for age). See Rural and remote health.

Socioeconomic area

Overweight and obesity rates differ across socioeconomic areas, with the highest rates in the lowest socioeconomic areas.

In 2017–18, obesity rates for children and adolescents aged 2–17 were 2.4 times as high in the lowest socioeconomic areas (11%) compared with the highest socioeconomic areas (4.4%). For overweight and obesity combined, rates were also higher in the lowest socioeconomic areas (28%) compared with the highest socioeconomic areas (21%) (ABS 2019).

Australians aged 18 and over in the lowest socioeconomic areas were more likely to be overweight or obese than those in the highest socioeconomic areas in 2017–18: 72% compared with 62% (after adjusting for age). Obesity rates were the underlying reason for this difference (38% compared with 24% respectively). See Health across socioeconomic groups.

Where do I go for more information?

For more information on overweight and obesity, see:

Visit Overweight & obesity for more on this topic.

References

ABS (Australian Bureau of Statistics) 2009. National Health Survey: summary of results, 2007–08 (reissue).  ABS cat. no. 4364.0. Canberra: ABS.

ABS 2013a. Australian Health Survey: updated results, 2011–12. ABS cat no. 4364.0.55.003. Canberra: ABS.

ABS 2013b. Microdata: National Nutrition Survey, 1995, Basic Confidentialised Unit Record File, DataLab. ABS cat. no. 4807.0.30.001. Findings based on AIHW analysis of ABS microdata. Canberra: ABS.

ABS 2015. National Health Survey: first results, 2014–15. ABS cat no. 4364.0.55.001. Canberra: ABS.

ABS 2018. National Health Survey: first results, 2017–18. ABS cat. no. 4364.0.55.001. Canberra: ABS.

ABS 2019. Microdata: National Health Survey 2017–18. ABS cat. no. 4324.0.55.001. AIHW customised data request. Canberra: ABS.

AIHW (Australian Institute of Health and Welfare) 2017. Impact of overweight and obesity as a risk factor for chronic conditions: Australian Burden of Disease Study. Australian Burden of Disease Study series no. 11. Cat. no. BOD 12. Canberra: AIHW.

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.

di Angelantonio E, Bhupathiraju SN, Wormser D, Gao P, Kaptoge S, de Gonzalez AB et al. 2016. Body-mass index and all-cause mortality: individual-participant-data meta-analysis of 239 prospective studies in four continents. The Lancet 388:776–86.