Overweight and obesity in Australia


Current Issues

Overweight and obesity in Australia

E-Brief: Online Only issued 5 October 2006

Mandy Biggs Analysis and Policy
Social Policy Section

Introduction

Reports of an obesity epidemic appear with increasing frequency and rising concern in Australia. Particular attention is given to reports of the accelerating rate of obesity among Australian children. Despite this high profile of obesity as a public health issue, some aspects of the debate rest on limited evidence and/or outdated data, including: out-dated national time trend data on children and inadequate measures of obesity and overweight.

This e-brief provides links to sources and an overview of the current state of obesity and overweight in Australia. Information on how overweight and obesity are measured is presented, followed by a brief discussion on the limitations of these measures. Prevalence data for obesity and overweight in children and adults is then presented and limitations of this data are discussed. The need for a national nutrition survey and recent developments in this area are discussed, and finally some links to information and sources are provided.

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How obesity is measured

Obesity is most commonly measured using the body mass index (BMI). BMI is a weight-to-height ratio, and is considered to be a reasonable reflection of body fat for most people. BMI is calculated by dividing body weight in kilograms by the square of height in metres (kg/m).

Among adults, a person with a BMI greater than 25kg/m is considered overweight, while a BMI greater than 30kg/m is considered obese. The table below shows the BMI cut-off points widely accepted for use among adults in Australia, and which relate to points where the risks of adverse health outcomes rise sharply.

Body mass index categories for adults in Australia

Source: NHMRC

International BMI-for-age tables were developed for children using the adult cut-off points as references. The Department of Health and Ageing has published these BMI-for-age-tables.

However, while recommending the use of BMI tables the National Health and Medical Research Council (NHMRC) in its Dietary Guidelines for Children and Adolescents, notes some limitations with the tables as they apply to children (see Part B of the chapter Special Considerations ). First, the cut-off points chosen to classify overweight and obesity in children are arbitrary, without evidence of an association with adverse health outcomes (unlike cut-off points for adults, which have been linked to adverse health outcomes).

Second, because Australia does not currently have growth reference charts derived from the local population, a reference from another population is used; currently the US National Center for Health Statistics (now the Centers for Disease Control) growth charts are used. However, these are based on data derived from infants who were not exclusively breastfed (formula fed babies tend to be heavier than breast fed babies).

Third, the BMI measure is not considered the most accurate measure of abdominal obesity (more accurate measures are magnetic resource imaging or dual energy X-ray absorptiometry). Lastly, the NHMRC notes that BMI does not allow for ethnic variations in weight and fat distribution.

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Prevalence - Children

Measuring obesity in children can be problematic due to differences in developmental rates and maturation.

Further, recent national time trend data on the prevalence of obesity in Australian children and adolescents are not available. The most recent national survey data come from the 1985 Australian Health and Fitness Survey (AHFS) and the 1995 National Nutrition Survey (NNS). Drawing on data from these surveys, which use the above BMI tables to define overweight and obesity, the Australian Institute of Health and Welfare (AIHW) reported the following prevalence rates in a recent brief:

  • 15.3% of boys and 16.0% of girls (aged 7 15 years), were overweight in 1995, compared to 9.3% of boys and 10.6% of girls in 1985
  • 4.7% of boys and 5.5% of girls (aged 7 15 years) were obese in 1995, compared to 1.4% of boys and 1.2% of girls in 1985
  • 21.5% of girls and 20% of boys were either overweight or obese in 1995, and
  • in the ten year period from 1985 to 1995 the prevalence of obesity alone among 7 15 year-olds more than tripled.

See the figure below:

Prevalence of overweight and obesity among boys and girls aged 7-15 years, 1985 and 1995

Source: AIHW

Detailed analysis of age group data undertaken by the AIHW in the recent brief, shows that the prevalence of overweight and obesity varies considerably across sex and age levels:

  • In 1995 boys aged 10 14 had the highest levels of overweight (18.3%), while for girls those aged 2 4 had the highest levels (18.5%)
  • the highest levels of obesity for boys occurred among the 15 17 year old age group (6.1%), and for girls among the 5 9 year old age group (7.1%)
  • 15.3% of 2 17 year olds were overweight and 4.6% obese, and
  • overall, one in five or 19.9% of Australian children aged 2 17 were overweight or obese in 1995.

See figure below:

Prevalence of overweight and obesity among boys and girls aged 2-17 years, 1995 by age group

Source: AIHW

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Other Australian data

Citing data from more recent regional and state surveys of school students, the AIHW s brief concludes that the rates of overweight and obesity among young Australians are accelerating. This data includes:

  • a 2000 survey of NSW primary school children aged 7 11, where the prevalence of overweight was reported at 26.2% of boys surveyed and 28.4% of girls, while the prevalence of obesity was reported at 9.9% of boys and 7.1% of girls (all increases from the levels reported in the NNS in 1995)
  • the 2003 Sentinel Site for Obesity Prevention in Victoria study which reported that 26.7% of 7 11 year olds surveyed were classed as overweight, while 7.9% were classed as obese
  • analysis of data collected in state surveys between 1967 and 1997 shows that from the mid-1980s to the mid-1990s the prevalence of obesity tripled and that of overweight doubled among 7 15 year olds, compared with a much smaller rate of increase over the preceding 16 years.

However, it is unclear if this accelerated trend is continuing. Recently released data from the NSW Schools Physical Activity and Nutrition Survey in 2004 found that of the 5 16 year olds surveyed, 25% of boys and 23.3% of girls were either overweight or obese (up from the 1995 data but similar to results reported in 2000 and 2003).

Other data indicates that obesity may be developing at a much younger age. According to recent research from South Australia cited in the AIHW brief, the percentage of obese preschoolers (children aged four years) in South Australia rose from 3.5% for girls and 3.2% for boys in 1995 to 5.8% for girls and 4.1% for boys in 2002.

As can be seen from the table below, international comparisons of obesity are especially problematic for children, because of the different age ranges that are measured and differences in the years in which surveys are conducted.

International comparisons of obesity among children, 1992-2002

Source: AIHW

Despite the data presented from these surveys and studies, the absence of a recent national nutrition survey means that accurate and reliable nutritional and energy intake data on Australian children is missing.

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Prevalence - Adults

The most recent national data on overweight and obesity for adults (aged 18 75) is based on self-reported BMI data from the 2004 05 National Health Survey (NHS). It should be noted that self-reported data is considered less reliable than measured data (because people tend to overestimate their height and underestimate their weight). The survey showed that:

  • overall 32.6% of adults were reported as overweight in 2004 05
  • 40.5% of males and 24.9% of females were overweight
  • overall 16.4% of adults were reported as obese in 2004 05
  • 17.8% of males and 15.1% of females were obese.

The NHS showed higher rates of overweight or obesity in older age groups. Those in the 55 64 age group had the highest combined rates of overweight and obesity; 72% of males and 58% of females.

The prevalence of overweight and obesity increased markedly between 1995 and 2004 05, according to historical data presented in the 2004-05 NHS. Levels of overweight increased from 29.5% reported in the 1995 NHS to 32.6% in 2004-05. At the more severe end of the spectrum, the prevalence of obesity among Australian adults was 11.1% in 1995, rising to 16.4% 2004 05.

In Australia s Health 2006, the AIHW reports a similar prevalence of overweight and obesity in Australian adults across the states and territories, according to analysis it undertook on figures derived from the NHS. Obesity rates ranged from 17.0% in Victoria to 19.6% in South Australia, and overweight rates from 34.2% in Queensland to 36.3% in Victoria.

Measured height and weight data were also collected nationally in the 2000 AusDiab study, and in the 2005 follow up study. Analysis of AusDiab data by the AIHW reported in Australia s Health 2006, found that of those surveyed 19% of males and 22% of females aged 25 years or over were obese and an additional 48% of males and 30% of females were overweight in 1999 2000. In this sample, males were more likely than females to be overweight or obese (67% versus 52%). The prevalence of obesity was found to be highest among those aged 55 64 (29%), with the lowest rates being among those aged 25 34 (15%) or 75 years and over (14%). Prevalence patterns for all overweight people were similar, with the prevalence increasing with age to 65 74 years, and declining thereafter.

The 2005 AusDiab follow up study by Barr et al, found that over the period of follow up there was an increase in average weight, BMI and waist circumference in both males and females. On average those aged under 65 at baseline showed a weight increase of 1.8 kg (those aged 65 74 showed a slight decline in weight, but an increase in BMI).

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International comparisons

As noted above international comparisons on obesity can be problematic because data is not always directly comparable. However, recent data indicates that the prevalence of overweight adult Australians is similar to that in the US, Canada and the UK; prevalence of obesity is lower than the US, but similar to both the UK and Canada. See figure below:

Prevalence of overweight and obesity 2002

Source: AIHW

In its recent survey of chronic disease risk factors, the World Health Organisation estimated that 75.7% of males and 66.5% of females in Australia will be overweight by 2010, and 28.4% of adult males and 29.1% of adult females will be obese, if current trends continue.

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A national survey

Despite the range and type of overweight and obesity data available (as is shown in the data presented here), it has been noted by public health and nutrition experts that Australia has lacked consistent national data on nutrition and energy intake. In the last 50 years Australia has conducted only three national surveys of diet: a survey of adults in 1983, of children in 1985, and the NNS in 1995, which surveyed both adults and children. Each of these surveys was conducted by a different agency using different survey techniques, making ongoing analysis of nutrition and energy intake over time difficult to undertake, and limiting our ability to understand trends in food and nutrient consumption.

In 2005 the federal government announced funding of $3m for a joint Australian government/food industry initiative called Measuring Australia s eating habits and physical activity, to collect national data on nutrition and physical activity. The project is a joint initiative of the Department of Health and Ageing, the Department of Agriculture, Fisheries and Forestry and the Australian Food and Grocery Council, which are each contributing $1m to the project.

In April 2006 the AMA criticised the project, describing it as underfunded and calling for a government funded national nutrition survey. Also in April the report A national food and nutrition monitoring surveillance system commissioned by the Department of Health and Ageing was released, which noted the ongoing and overwhelming support from stakeholders for a national nutrition surveillance system. The report estimated that the cost of establishing and maintaining an annual nutrition survey would be $1.2 million annually.

Further details of the joint initiative were announced in July 2006, including that the national nutrition and physical activity survey will be undertaken by the CSIRO and the University of South Australia for completion before 2007. Furthermore, the Department had committed annual funding of $1m a year for a national ongoing program to collect data on food, nutrition, physical activity habits, and physical measurements of all population groups.

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Links to sources

Australian Institute of Health and Welfare

A growing problem. Trends and patterns in overweight and obesity among adults in Australia, 1980 to 2001.

Are all Australians gaining weight? Differentials in overweight and obesity among adults, 1989-90 to 2001.

A rising epidemic: obesity in Australian children and adolescents

Obesity trends in older Australians.

Health, wellbeing and body weight: characteristics of overweight and obesity in Australia, 2001 and Physical activity, diet and body weight: results from the 2001 National Health Survey.

The health and welfare of Australia s Aboriginal and Torres Strait Islander people, chapter 8, Health risk factors

See also Australia s health 2006 chapter 3 section on biomedical determinants of health.

Other sources/information

T. Abbott, National children s survey to help tackle obesity Media Release 19 July 2006.

ABS National Health Survey 2004-05: Summary of results

ELM Barr, et al., AusDiab 2005: the Australian diabetes, obesity and lifestyle study International Diabetes Institute, Melbourne, 2006. (Executive summary only available online)

Booth, M, Okely AD, Denney-Wilson, E, Hardy L, Yang, B, Dobbins T, NSW Schools Physical Activity and Nutrition Survey (SPANS) 2004 Summary Report. NSW Health, 2006.

Centers for Disease Control National Center for Health Statistics (US) 2000 CDC Growth charts: United States

Department of Health and Ageing Healthy Weight website.

D Dunstan, et al, The Australian Diabetes, Obesity and Lifestyle report (AusDiab) 2000 International Diabetes Institute, 2001.

International Obesity Taskforce Obesity in children and young people: a crisis in public health: report to the World Health organization Obesity Reviews vol 5 (supp 1) May 2004

P McGauran, and C Pyne, New $3m project to help tackle childhood obesity Press release, 13 September 2005

National Health and Medical Research Council Dietary guidelines for children and adolescents in Australia NHMRC, 2003.

National Health and Medical Research Council Dietary guidelines for Australian adults NHMRC, 2003.

Nexus Management Consulting. A national food and nutrition monitoring and surveillance system: a framework and a business case: Final report April 2006.

Department of Human Services, Victoria Information about the growth charts: key questions (CDC growth charts)

KL Webb, IH Rutishauser, GC Marks, G Masters, SR Leeder, Nutrition surveys or surveillance: one night stands or a long term commitment? Medical Journal of Australia vol 185 (5) pp 248-249.

WHO The SuRF Report 2: Surveillance of chronic disease Risk Factors WHO, 2005.

 

For copyright reasons some linked items are only available to members of Parliament.

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