Overweight and obesity

Excess body weight, known as overweight and obesity, is a risk factor for many conditions, including cardiovascular disease, high blood pressure, type 2 diabetes, sleep apnoea and osteoarthritis. Overweight and obesity is among the leading causes of death and disability in Australia (AIHW 2019a).

Body Mass Index (BMI)

One way of measuring excess body weight at the population level is to use the body mass index (BMI)—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. Differences in body composition may affect the appropriateness of BMI, and different BMI cut-off points may need to be considered for certain population groups such as:

  • older people
  • people with high muscle mass
  • certain ethnic groups, including Aboriginal and Torres Strait Islander, Pacific Islander, South Asian, Chinese and Japanese populations (NHMRC 2013).

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).

Information in this section relates to measures of overweight and obesity as estimated using BMI.

3 in 5

Australian women are overweight or obese

 According to 2017–18 data (ABS 2018):

  • 3 in 5 Australian women (60%) were overweight or obese
  • 3 in 10 (30%) were overweight (but not obese)
  • 3 in 10 (30%) were obese.

Overweight and obesity is more common in older age groups. Around 3 in 4 women (73%) aged 65–74 were overweight or obese, compared with 2 in 5 women (40%) aged 18–24 (ABS 2018).

The proportion of women who were overweight or obese varied for some population groups. After adjusting for age (ABS 2013, ABS 2019c):

  • women living in Outer regional and remote areas were 1.2 times as likely to be overweight or obese as women in Major cities (66% and 57%, respectively)
  • women living in the lowest socioeconomic areas were 1.3 times as likely to be overweight or obese as women in the highest socioeconomic areas (66% and 50%, respectively)
  • in 2012–13, 7 in 10 (70%) Aboriginal and Torres Strait Islander women were overweight or obese. After adjusting for differences in age structure, the rate of overweight and obesity in Aboriginal and Torres Strait Islander women was 1.3 times the rate in non-Indigenous women (73% compared to 55%).

The proportion of females who were overweight or obese in 2017–18 differed between women and girls (ABS 2019c):

  • more than half (60%) of women aged 18 and over were overweight or obese
  • less than 1 quarter (24%) of girls aged 2–17 were.

Overweight and obesity among girls aged 2–17 varied for some population groups (ABS 2019c):

  • girls living in the lowest socioeconomic areas were 1.5 times as likely to be overweight or obese as girls in the highest socioeconomic areas (31% and 21%, respectively).

Figure 7: Body mass index, girls aged 2–17 and women aged 18 and over, 2017–18

This figure is comprised of two pie charts. The first shows that, for girls aged 2–17, 8.3%25 were underweight, 68%25 were normal weight, 16%25 were overweight and 7.4%25 were obese. The second pie chart shows that, for men aged 18 and over, 1.7%25 were underweight, 39%25 were normal weight, 30%25 were overweight and 30%25 were obese.

Note: Totals may not add to 100% due to rounding. 
Chart: AIHW. Source: ABS 2018 (see Tables S5 and Table S6 for footnotes).

For more information see Overweight and obesity.

Waist circumference

Waist circumference is another common measure of overweight and obesity. For women, a waist circumference above 80cm is associated with an increased risk of metabolic complications and above 88cm a substantially increased risk (WHO 2011).

2 in 3

Australian women have a waist circumference associated with increased or substantially increased metabolic risk

According to 2017–18 data, 2 in 3 Australian women (66%) had a high-risk waist circumference—that is, one associated with an increased or substantially increased risk of metabolic complications (Figure 8). The average waist circumference for women aged 18 and over in 2017–18 was 88 cm (ABS 2018).

A high-risk waist circumference is more common in older women. In 2017–18 (ABS 2019):

  • around 4 in 5 women aged 75 and over (84%) had a high risk waist circumference
  • around 2 in 5 women aged 18–24 (37%) did.

The prevalence of high-risk waist circumference varied for some population groups. After adjusting for age (ABS 2019a):

  • women living in Inner regional areas were 1.1 times as likely to have a high-risk waist circumference as women in Major cities (69% and 63%, respectively)
  • women living in the lowest socioeconomic areas were 1.3 times as likely to have a high-risk waist circumference as women in the highest socioeconomic areas (71% and 56%, respectively).

Figure 8: Waist circumference, women aged 18 and over, by risk category, 2017–18

This pie chart shows that 34%25 of women were in the ‘not at risk category’, 20%25 in the ‘increased risk’ category, and 46%25 were in the ‘substantially increased risk’ category.

Note: Totals may not add to 100% due to rounding. 
Chart: AIHW. Source: ABS 2019a (see Table S7 for footnotes).

Management of overweight and obesity

While excess weight is commonly managed using dietary intervention and exercise, for those who are morbidly obese, or who are obese and have other conditions related to their excess weight, weight loss surgery may be appropriate.

Weight loss surgery (bariatric surgery) aims to help obese patients lose weight and lower the risk of medical problems associated with obesity. It restricts the amount of food a recipient can eat or alters the process of food digestion so that fewer calories are absorbed.

In 2017–18, females accounted for 80% of procedures for weight loss surgery (31,600 procedures). The rate of weight loss surgeries among females for the same year was 251 per 100,000, an increase from 2015–16 with 23,663 procedures and a rate of 194 per 100,000 (AIHW 2019b).

For more information see Weight loss surgery in Australia 2014–15.