Being overweight or obese is a risk factor for colorectal, breast (post-menopause), oesophageal (adenocarcinoma), endometrial, pancreatic, liver and kidney cancers.1, 2 The estimated percentage of cancers attributable to overweight and obesity ranges from 4.5% of cancer cases in Europe3 to 20% in the United States.4 It is estimated that 3.6% of all new cancers in adults worldwide are attributable to excess bodyweight.5
As the analysis for this measure shows, overweight and obesity are an important cancer control measure to monitor due to the marked variations in prevalence between population groups at the national level (e.g., groups classified by sex, area socioeconomic level, and residential remoteness etc).
Charts
About this measure
Overweight and obesity is calculated using the Body Mass Index (BMI), a scale based on height and weight commonly used to define whether a person is underweight, normal weight, overweight or obese.6-8 BMI is calculated by dividing a person’s weight (in kilograms) by their height (in meters). Guidelines established by the World Health Organisation8 and the National Health and Medical Research Council7 place adults aged 18 years and older into the following categories based on their BMI.
Table 1: Classifications of BMI for adults aged 18 years and over
| BMI (kg/m2 | Classification |
| Less than 18.5 | Underweight |
| 18.5 to less than 25 | Normal weight |
| 25 to less than 30 | Overweight |
| 30 or more | Obese |
| 35 or more | Morbidly obese |
Where relevant, rates were age-standardised for this measure to account for differences in age structure over time. Age-standardisation was also applied for comparisons between population groups, including:
- people by Indigenous and non-Indigenous status
- area of residential remoteness
- area level of socioeconomic disadvantage.
Current status
In 2017-18, an estimated 12.5 million Australian adults (67% of the adult population) aged 18 years and over were overweight (36%) or obese (31%), with the prevalence being higher among males than females (74.5% compared with 60%).9 This can be attributed to a higher proportion of males being overweight compared with females (42% compared with 30%) while the obesity rates were similar for both sexes.
The prevalence of adults being overweight or obese increased with age, peaking at 55-64 years for males (84%) and at 65-74 years for females (73%), before decreasing to 75% of males and 69% of females aged 75 years and over.9 The proportion of overweight and obese males was significantly higher than for females across all age groups. The greatest difference between males and females in the proportion of overweight or obese was observed among age group 45-54 years (83% compared to 65%, respectively).
Morbidly obese
In 2017-18, one in ten Australian adults (12%) had a BMI score of 35 or more, putting them in the morbidly obese category.9, 10 This corresponded to 1 in every 3 obese people being morbidly obese. Females were more likely to be morbidly obese than males (12.5% compared with 11%, respectively).
The proportion of people who were morbidly obese generally increased from age group 25-34 years, peaking at 65-74 years for males (14%) and females (16%).9, 10 Thereafter, rates decreased for both males (7%) and females (12%) aged 75 years and over.
Aboriginal and Torres Strait Islander peoples
In 2018-19, 77% of Aboriginal and Torres Strait Islander peoples were overweight (30%) or obese (47%).11 Although the combined overweight and obesity rates were similar between males and females, obesity was more common among females than males (49.1% compared with 45.0%) while overweight rates were higher among males than females (32% compared with 28%).
The proportion of overweight or obese Aboriginal and Torres Strait Islander peoples generally increased with age, reaching a maximum of 82% among those aged 55 years and over.11 While the overweight rates were similar across all age groups, the proportion of obese adults generally increased with age, peaking at 31% in those aged 35-44 years.
After adjusting for differences in age structure for both Indigenous and non-Indigenous populations, Indigenous Australians were 1.2 times more likely to be overweight or obese than non-Indigenous Australians (77% compared with 66%).11 Indigenous Australians were 1.5 times as likely as non-Indigenous Australians to be obese (rate ratio 1.4 for males and 1.7 for females).
Remoteness and socioeconomic status (SES)
The proportion of adults who were overweight or obese in 2017-18 varied according to geographic regions and level of socioeconomic disadvantage. After adjusting for differences in age structure, adults in Inner Regional (72%), and Outer Regional and Remote areas (72%) were more likely to be overweight or obese than those in Major cities (65%).9, 10 This was mainly due to higher rates of obesity among both males and females living in Inner Regional (39% for males and 36% for females), and Outer Regional and Remote areas (36% for males and 38% for females) compared with those living in Major cities (30.5% for males and 28% for females).
In 2017-18, a higher proportion of people living in lowest SES areas were overweight or obese compared with those living in the highest SES areas (72% compared with 63%).9, 10 The social gradient of obesity showed that proportionally people living in lowest SES areas were 1.5 times more likely to be obese than those living in the highest SES areas (38% compared with 25%, respectively).10
Trends
The proportion of overweight or obese adults has increased from 1995 to 2017-18.9, 10, 12-17 After adjusting for differences in age structure over time, the proportion of overweight or obese adults increased from 57% in 1995 to 66% in 2017-18. This change was largely as result of an increase in levels of obesity, from 19% in 1995 to 32.5% in 2017-18 for males and from 19.% in 1995 to 30% in 2017-18 for females. Increases were observed across almost every age group. By comparison, the proportion of overweight adults decreased from 38% in 1995 to 36% in 2017-18.
Remoteness and socioeconomic status (SES)
After adjusting for differences in age structure, the proportion of overweight or obese adults remained unchanged between 2014-15 and 2017-18 across different geographic regions of Australia.9, 10,17 However, among males living in Inner Regional areas, there was a significant increase in the proportion who were obese (from 33% in 2014-15 to 40% in 2017-18) while at the same time there was an increase in the proportion of males who were overweight living in Outer Regional and Remote areas (from 34% in 2014-15 to 40% in 2017-18). For females, there were no changes in proportion of people who were overweight or obese across different geographic regions of Australia.
The age-standardised rates of overweight and obesity were similar across different SES areas between 2014-15 and 2017-18.9, 10,17
International Comparison (15 years and over)
The increasing prevalence of overweight and obesity is a major public health concern worldwide.18 The latest results showed that one in two adults in Organization of Economic Cooperation and Development (OECD) countries are overweight or obese.18 Australia has comparatively high prevalence of obesity in a global context – ranking 6th highest (30%) among 16 OECD countries with measured BMI data.
About the data
This measure shows the proportions of people who were overweight or obese.
Numerator: Number of persons aged 18 years and over who were overweight or obese (i.e. BMI score of 25 or greater).
Denominator: Number of persons aged 18 years and over having their height and weight measured.
In the Index of Relative Socio-Economic Disadvantage, attributes summarised by this index include low income, low educational attainment, high unemployment and jobs in relatively unskilled occupations. A lower Index of Disadvantage quintile (e.g. the first quintile) indicates an area with relatively greater disadvantage and a lack of advantage in general. A higher Index of Disadvantage (e.g. the fifth quintile) indicates an area with a relative lack of disadvantage and greater advantage in general.
BMI score: overweight = 25 to less than 30; obese = 30 or greater; morbidly obese = 35 or greater.
Methodology
Proportions have been age standardised to the 2001 Australian population to account for differences in age structures between the populations.
The 2011-12, 2014-15 NHS data in TableBuilder and 2017-18 NHS data have been randomly adjusted to avoid the release of confidential data. Discrepancies may occur between sums of the component items and totals.
Remoteness
The Australian Statistical Geography Standard (ASGS), was used to allocate participants to a remoteness area based on their area of usual residence. (Note that earlier data may have used the ASGS 2011 and superseded 2006 Australian Standard Geographical Classification (ASGC)).
Socioeconomic status
The 2016 Socio-Economic Indexes for Areas (SEIFA) Index of Relative Socio-Economic Disadvantage (IRSD) was used to allocate participants to a SEIFA quintile based on their usual residence (For 2011-2012 and 2014-2015 data the 2011 IRSD was used).
Data sources
ABS 1995 National Nutrition Survey
ABS 2011-12 Australian Health Survey – Core Content
ABS 2012-13 Australian Aboriginal and Torres Strait Islander Health Survey – Core Content
ABS 2007-08, 2014-15 and 2017-18 National Health Survey
OECD.Stat. Health Statistics (database). Non-medical determinants of health. OECD; 2020. https://stats.oecd.org/Index.aspx?QueryId=30128
Data caveats
Although BMI is correlated with body fat, it does not measure body fat directly or the distribution of body fat.6 Therefore, two individuals with the same BMI can have very different patterns of body fat distribution which contribute different levels of risk of developing chronic diseases. However, BMI is a simple tool in measuring and monitoring trends in overweight and obesity across different populations.
The calculation of BMI is based on measured height and weight data collected from the Australian Bureau Statistics 1995 National Nutrition Survey, 2011-12 Australian Health Survey – Core Content, 2012-13 Australian Aboriginal and Torres Strait Islander, 2018-19 National Aboriginal Torres Strait Islander Health and 2007-08, 2014-15 and 2017-18 National Health Survey.9-17
Table 2 presents the proportions of persons aged 18 years and over who did not have their height and/or weight measured across the survey years:
| Survey Year | Height and/or weight not measured (%) |
|---|---|
| 1995 | N/A |
| 2007-08 | 28.6 |
| 2011-12 | 15.8 |
| 2012-13 | 15.0 |
| 2014-15 | 26.8* |
| 2017-18 | 33.8* |
* For these respondents, imputation was used to obtain height, weight and BMI scores.
International comparisons
International comparisons were based on persons aged 15 years and overusing measured data. The most recent year for international data varies between 2012 and 2019. Data sourced from OECD.Stat. Health Statistics as at 14 July 2020.
The most recent year for data available by country is as follows:
| Country | Most recent year |
| New Zealand | 2020 |
| Ireland | 2019 |
| Turkey | 2017 |
| United States | 2019 |
| Mexico | 2018 |
| United Kingdom | 2019 |
| Chile | 2016 |
| Korea | 2019 |
| Japan | 2019 |
| Canada | 2019 |
| France | 2015 |
| Hungary | 2019 |
| Australia | 2017 |
| Belgium | 2018 |
| Germany | 2012 |
| Finland | 2017 |
References
Data
Australian Bureau of Statistics. 4364.00.55.001 – National Health Survey: First Results 2017-18. Canberra: ABS; 2018 [Accessed June 2022]; Available at: https://www.abs.gov.au/statistics/health/health-conditions-and-risks/national-health-survey-first-results/latest-release
Australian Bureau of Statistics. 4715.0 – National Aboriginal and Torres Strait Islander Health Survey, 2018-19. Canberra: ABS; 2019; [Accessed June 2022]; Available at: https://www.abs.gov.au/statistics/people/aboriginal-and-torres-strait-islander-peoples/national-aboriginal-and-torres-strait-islander-health-survey/2018-19
Social Health Atlases of Australia: Population Health areas – Health risk factors, data; [Accessed March 2020]; Available at: http://phidu.torrens.edu.au/social-health-atlases/data#social-health-atlas-of-australia-population-health-areas
Organisation for Economic Co-operation and Development (OECD) 2021. OECD.Stat. Paris. https://stats.oecd.org/index.aspx?DataSetCode=HEALTH_STAT#
Policy
National Health and Medical Research Council. Clinical Practice Guidelines for the Management of Overweight and Obesity in Adults, Adolescents and Children in Australia (2013). NHMRC: Canberra; 2013; [Accessed March 2020]; Available at: https://nhmrc.gov.au/about-us/publications/clinical-practice-guidelines-management-overweight-and-obesity
References
1. Cancer Australia. Lifestyle risk factors and the primary prevention of cancer. Sydney: Cancer Australia; 2015 [Accessed March 2020]; Available at: http://canceraustralia.gov.au/publications-and-resources/position-statements/lifestyle-risk-factors-and-primary-prevention-cancer.
2. World Cancer Research Fund/American Institute for Cancer Research. Food, nutrition, physical activity, and the prevention of cancer: a global perspective. Washington, DC: American Institute for Cancer Research; 2007.
3. Stewart BW. Priorities for cancer prevention: lifestyle choices versus unavoidable exposures. The Lancet Oncology. 2012;13(3):e126-33. Epub 2012/03/03.
4. Colditz GA, Wolin KY, Gehlert S. Applying what we know to accelerate cancer prevention. Sci Transl Med. 2012;4(127):127rv4.
5. Arnold M, Pandeya N, Byrnes G, Renehan AG, Stevens GA, Ezzati M, et al. Global burden of cancer attributable to high body-mass index in 2012: a population-based study. The Lancet Oncology. 2015;16(1):36-46. Epub 2014/12/04.
6. Center for Disease Control. Body Mass Index: Considerations for Practitioners. Atlanta, GA: Department of Health; 2015 [Accessed March 2020]; Available at: http://www.cdc.gov/obesity/downloads/bmiforpactitioners.pdf
7. National Health and Medical Research Council. Clinical Practice Guidelines for the Management of Overweight and Obesity in Adults, Adolescents and Children in Australia. Canberra: NHMRC; 2013 [Accessed March 2020]; Available at: https://www.nhmrc.gov.au/about-us/publications/clinical-practice-guidelines-management-overweight-and-obesity
8. World Health Organization. Obesity and overweight. Geneva: WHO; 2016 [Accessed March 2020]; Available at: http://www.who.int/mediacentre/factsheets/fs311/en/
9. Australian Bureau of Statistics. 4364.0.55.001 - National Health Survey, 2017-18. Canberra: ABS; 2018 [Accessed March 2020]; Available at: https://www.abs.gov.au/ausstats/abs@.nsf/PrimaryMainFeatures/4364.0.55.001?OpenDoc
10. 4324.0.55.001 - Microdata: National Health Survey, 2017-18 [database on the Internet]. ABS. 2018 [Accessed March 2020].
11. Australian Bureau of Statistics. 4715.0 – National Aboriginal and Torres Strait Islander Health Survey, 2018-19. Canberra: ABS; 2019; [Accessed June 2022]; Available at: https://www.abs.gov.au/statistics/people/aboriginal-and-torres-strait-islander-peoples/national-aboriginal-and-torres-strait-islander-health-survey/2018-19
12. Australian Bureau of Statistics. 4805.0 - National Nutrition Survey: Nutrient Intakes and Physical Measurements, Australia, 1995. Canberra: ABS; 1998 [Accessed March 2020]; Available at: http://www.abs.gov.au/AUSSTATS/abs@.nsf/Lookup/4805.0Main+Features11995?OpenDocument
13. Australian Bureau of Statistics. 4362.0 - National Health Survey: Summary of Results, 2007-2008 (Reissue) Canberra: ABS; 2009 [Accessed March 2020]; Available at: http://www.abs.gov.au/AUSSTATS/abs@.nsf/Latestproducts/4364.0History%20of%20Changes02007-2008%20(Reissue)?opendocument&tabname=Summary&prodno=4364.0&issue=2007-2008%20(Reissue)&num=&view=
14. Australian Bureau of Statistics. 4364.0.55.003 - Australian Health Survey: Updated Results, 2011-2012. Canberra: ABS; 2013 [Accessed March 2020]; Available at: http://www.abs.gov.au/ausstats/abs@.nsf/Lookup/4364.0.55.003main+features12011-2012
15. 4324.0.55.003 - Microdata: Australian Health Survey, Core Content - Risk Factors and Selected Health Conditions, 2011-12 [database on the Internet]. ABS. 2014 [Accessed March 2020]. Available at: http://www.abs.gov.au/ausstats/abs@.nsf/Lookup/4324.0.55.003main+features12011-12
16. Australian Bureau of Statistics. 4125.0 - Gender Indicators, Australia, August 2016. Canberra: ABS; 2016 [Accessed March 2020]; Available at: http://www.abs.gov.au/ausstats/abs@.nsf/mf/4125.0
17. Australian Bureau of Statistics. 4364.0.55.001 - National Health Survey: First Results, 2014-15. Canberra: ABS; 2015 [Accessed March 2020]; Available at: http://www.abs.gov.au/ausstats/abs@.nsf/PrimaryMainFeatures/4364.0.55.001?OpenDocument
18. Organization for Economic Cooperation and Development. "Obesity Update 2017", OECD Publishing; 2017 [Accessed March 2020]; Available at: https://www.oecd.org/health/health-systems/Obesity-Update-2017.pdf