Article: Overweight and obesity in Australian Social Trends 2007

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Australian Social Trends
2007
Article: Overweight and
obesity
Susan Linacre
Acting Australian Statistician
AUSTRALIAN BUREAU OF STATISTICS CATALOGUE NO. 4102.0
ABS catalogue no. 4102.0
ISSN 1321–1781
© Commonwealth of Australia 2007
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INQUIRIES
Where figures have been rounded, discrepencies may occur between the sums of the component items
and totals.
1,000 million
kilogram
metre
not available
not elsewhere classified
not published
not yet available
number
thousand
thousand million
dollar
million dollars
billion dollars
American dollar
per cent
estimate has a relative standard error of 25% to 50% and should be used with caution
estimate has a relative standard error of greater than 50% and is considered too unreliable
for general use
not applicable
nil or rounded to zero (including null cells)
billion
kg
m
n.a.
n.e.c
n.p.
n.y.a.
no.
'000
'000m
$
$m
$b
$US
%
*
**
. .
—
SYMBOLS AND USAGES
Overweight and obesity have become
world-wide concerns, reaching epidemic
proportions.1 Obesity is caused by an energy
imbalance where energy intake exceeds
energy expended over time.2 This imbalance
has been linked to lifestyle factors such as
increased consumption of foods with high
levels of sugar and saturated fats, as well as a
reduction in physical activity.
Overweight and obesity pose a major risk to
long term health by increasing the risk of
chronic illnesses such as diabetes,
cardiovascular disease and some cancers.1 It
has been estimated that obesity and its
associated illnesses cost Australian society
and governments a total of 21 billion in
2005.3 In July 2006, the Australian Government
implemented a five year, 500 million program,
the Australian Better Health Initiative, aimed
at reducing the impacts of chronic disease
which includes a focus on promoting healthy
weight.4
This article discusses adults who were
classified as overweight or obese according to
their Body Mass Index (BMI), based on
self-reported height and weight.
Overweight and obesity trends
In 2004–05, more than half (54%) of all
adults, or 7.4 million people aged 18 years
and over were either overweight or obese, an
increase from 45% (5.4 million adults) in
1995. Using age standardised data, the rate of
overweight adults has increased from 33% in
A B S • A U S T R A L I A N S O C I A L T R E N D S • 4 1 0 2 . 0 • 2 0 0 7 1
Overweight and obesity
Data sources and definitions
Data in this article are mainly drawn from the 1995,
2001 and 2004–05 National Health Surveys (NHS),
and refer to adults aged 18 years and over.
In the NHS, overweight and obesity are assessed
using body mass index (BMI), calculated from selfreported
height and weight information, using the
formula weight (kg) divided by the square of height
(m). To produce a measure of the prevalence of
overweight or obesity in adults, BMI values were
grouped according to the following categories:
Underweight (BMI less than 18.5), Normal (BMI
18.5 to less than 25.0), Overweight (BMI 25.0 to less
than 30.0) and Obese (BMI 30.0 and greater). BMI
rates calculated in this article include persons
whose BMI was underweight, but excludes persons
whose BMI was not stated or not known.
While BMI is a useful tool for assessing changes in
body mass at the population level, it may be less
appropriate for certain individuals. For example, it
does not account for those with high body mass
due to muscle rather than fat.
Self-reported height and weight may also differ
from measured height and weight. In 1995, a
comparison of these two methods suggested that
when self-reporting, people tend to overstate their
height and understate their weight. For further
details, see How Australians Measure Up, 1995
(ABS cat. no. 4359.0).5
To account for any variations in age structure of the
population over time as well as between certain
sub-populations, rates and proportions are age
standardised to the 2004–05 total NHS population
where applicable.
In 2005, 7.4 million
people aged 18 years
and over (54% of the
adult population) were
classified as
overweight or obese.
(a) Based on self-reported height and weight.
(b) Total includes persons whose BMI was underweight.
(c) Age standardised to 2004–05 total NHS population.
Source: ABS 1995, 2001 and 2004–05 National Health Surveys.
1995(c) 2001(c) 2004–05
%
0
10
20
30
40
50
60
70 Normal
Overweight
Obese
1995(c) 2001(c) 2004–05
%
0
10
20
30
40
50
60
70 Normal
Overweight
Obese
FEMALES MALES
Adults in normal, overweight and obese BMI(a) categories(b)
1995 to 36% in 2004–05, while the rate of
obesity in adults has increased from 13% to
18% over the same period. Each of the
National Health Surveys conducted since
1995 has reported a higher rate of overweight
and obesity for males than for females.
Obesity in adults
Rates of overweight and obesity vary
depending on age and sex. Between 1995
and 2004–05, rates of obesity increased for
both men and women across all age groups.
For men, the largest increase in the obesity
rate occurred in the 35–44 age group which
almost doubled from 12% in 1995 to 23% in
2004–05. For women, the increase in the
obesity rate was more uniform across age
groups.
Although the National Health Surveys collect
data at one point in time, it is possible to
observe changes over time in the obesity rate
for a cohort of people born in the same ten
year period. In this approach, for example,
survey respondents aged 25–34 years in 1995
and those aged 35–44 years in 2004–05, while
not the same respondents, are seen as
representing the same group of people as
they age ten years. Among the male cohorts,
the greatest increase in the rate of obesity
occurred for the group aged 25–34 in 1995
(12% in that year compared to 23% ten years
on, in 2004–05).
For females, the greatest increase in the obesity
rate occurred for the cohort aged 35–44 years in
1995, with 12% classified as obese compared to
20% of the 45–54 year olds representing the
same group of people in 2004–05.
There were smaller increases in older
women, with 18% of those aged 55–64 years
classified as obese in 1995, compared to 22%
of 65–74 year olds representing the same
cohort in 2004–05. For men, rates over the
ten year period were similar, with 16% of
males aged 55–64 classified as obese in 1995,
and 17% of 65–74 year olds classified as
obese ten years later.
Socioeconomic characteristics
The NHS can provide insight into associations
between certain sociodemographic
characteristics and excess weight. As some of
these populations have differing age
structures, the proportions presented in this
section are age standardised to remove the
confounding influence of age.
...born overseas
Most people born overseas are in good health
on arrival in Australia due to the rigorous health
checks they undergo to be eligible for migration.
This 'healthy migrant effect' generally wanes as
their length of time in Australia increases, and
time since migration is an important factor in
excess weight in migrants.6
In 2004–05, the overall adult obesity rate was
18%. People born overseas who arrived before
1996 had a slightly lower age standardised rate
of obesity (15%), while the rate was even
lower (11%) for more recent arrivals (between
1996 and 2005).
2 A B S • A U S T R A L I A N S O C I A L T R E N D S • 4 1 0 2 . 0 • 2 0 0 7
Gaining weight
Between 1995 and 2004–05, the average weight
(kg) of both male and female adults increased
across all age groups. During this period, the
average weight of an adult female increased from
65kg to 68kg, and for males it increased from 80kg
to 84kg.
Men appear to be getting heavier at an earlier age.
In 1995, the average weight for males peaked in the
45–54 years age group (82kg). By 2004–05 average
weight was greatest in the 35–44 years group
(87kg) which was 6kg more than for this age group
in 1995. For women, the increases in average
weight were similar across all age groups.
Source: ABS 1995 and 2004–05 National Health Surveys.
18–24 25–34 35–44 45–54 55–64 65–74 75
and over
Age group (years)
%
0
5
10
15
20
25
30 1995
2004–05
18–24 25–34 35–44 45–54 55–64 65–74 75
and over
Age group (years)
%
0
5
10
15
20
25
30 1995
2004–05
FEMALES MALES
Obese adults by age
...education
Adults with a degree, diploma or higher
qualifications were less likely to be obese than
those with other or no post-school
qualifications. In 2004–05, around one-fifth
(21%) of those without a non-school
qualification, and 19% of those with other
non-school qualifications (i.e. trade certificate),
were classified as obese. By comparison, 13% of
those with a degree/diploma or higher
qualification were classified as obese.
...income
While equal proportions (53%) of people in
low income and high income households were
overweight or obese in 2004–05, those in low
income households were more likely to be
obese. Around one-fifth (21%) of adults in low
income households were obese compared
with 15% of adults in high income households.
...disadvantage
The Socio-Economic Indexes for Areas
(SEIFA) Index of Disadvantage summarises
various attributes (such as income and
unemployment) of an area in which a
population lives. In 2004–05, adults living in
areas of greatest relative disadvantage had a
higher age standardised rate of obesity (22%)
compared to adults living in areas with the
lowest relative disadvantage (13%).
A B S • A U S T R A L I A N S O C I A L T R E N D S • 4 1 0 2 . 0 • 2 0 0 7 3
(a) Sub-populations age standardised to 2004–05 total NHS population.
(b) Based on self-reported height and weight.
(c) Includes persons whose BMI was underweight.
(d) Gross weekly equivalised household income. Low income households are in the lowest quintile, middle income in the third
quintile and high income in the highest quintile of household income.
(e) The first quintile contains areas with the greatest relative disadvantage and the fifth quintile those areas with the lowest
relative disadvantage.
Source: ABS 2004–05 National Health Survey.
13 760.6 2 478.0 4 888.0 6 037.0 '000 All persons aged 18 years and over
100.0 18.0 35.5 43.9 % All persons aged 18 years and over
100.0 12.9 34.8 49.6 % Fifth quintile
100.0 22.4 34.5 40.0 % First quintile
Index of disadvantage(e)
100.0 14.9 37.8 45.5 % High income
100.0 17.4 35.8 43.8 % Middle income
100.0 20.8 32.4 43.1 % Low income
Household income(d)
100.0 20.5 35.6 41.1 % No non-school qualification
100.0 19.4 37.0 41.7 % Other qualification
100.0 13.0 34.9 49.2 % Degree/diploma or higher qualification
Highest non-school qualification
100.0 10.6 32.6 51.5 % Arrived 1996–2005
100.0 15.1 33.9 48.0 % Arrived before 1996
Born overseas
Total(c) Obese Overweight Normal Units
Age standardised socioeconomic characteristics(a) of adults and BMI(b) —
2004–05
Overweight and obesity in NSW
children
The 2004 NSW Schools Physical Activity and
Nutrition Survey (SPANS) provides insight into
overweight and obesity in children aged 5 to 16
years in NSW. Almost 5,500 school-aged children
from ages 5 to 16 years were surveyed and
measured for height and weight. BMI in childhood
changes substantially with age, thus children were
defined as healthy, overweight or obese using age
and gender-appropriate categories recommended
by the International Obesity Taskforce.7
Overall, 25% of boys and 23% of girls were either
overweight or obese. For boys, the rate of
overweight and obesity was related to age, reaching
a peak in 11–12 year olds (22% of this group
classified as overweight and 9% classified as obese)
before declining again. For girls, the highest rates
of overweight and obesity was in 9–10 year olds,
with 22% of this age group classified as overweight
and 8% classified as obese.7 See the NSW Schools
Physical Activity and Nutrition Survey (SPANS)
2004: Full Report for further information.
Aside from socioeconomic differences
between areas in terms of education, income
and employment, some areas may also offer
greater opportunities for physical activity and
greater access to healthy food options.8
...remoteness areas
In 2004–05 the rate of obesity in Outer
Regional/remote/very remote areas was 23%,
while in Major Cities and Inner Regional
areas the rates were 17% and 19%
respectively. The rate of overweight was
similar across the remoteness areas (36% in
Outer Regional/remote/very remote areas of
Australia, compared to 35% in Major Cities).
Perceptions of own weight
For many people, particularly men and older
women, self perception of 'acceptable weight'
differs from the standard BMI definitions.
This may have implications for the
management of healthy body weight in
adults.9 In 2004–05, more than half of adults
(63% of males and 59% of females)
considered themselves to be of acceptable
weight. The proportion of males (32%) and
females (38%) who considered themselves to
be overweight was considerably lower than
those who were classified as
overweight/obese according to their BMI
(62% and 45% respectively).
Between 1995 and 2004–05, after adjusting
for differences in the age structure of the
population, the proportion of people in the
overweight and obese BMI categories who
considered themselves to be of acceptable
weight increased. In 2004–05, almost half
(47%) of males and around one-fifth (21%) of
females who were overweight or obese
considered themselves to be of acceptable
weight. This compares with age standardised
rates of around one-third (35%) for males and
12% for females in 1995.
Health risk behaviours and relative
prevalence of long term conditions
Being overweight (i.e. BMI of 25 or more) is a
modifiable risk behaviour for a number of
long term health conditions, including a
number of National Health Priority Area
(NHPA) conditions, such as diabetes, arthritis
and some cancers.10 It is also associated with
a range of other NHPA risk factors, such as
high blood pressure and high blood
cholesterol.
In the following analysis, we include data on
two modifiable risk behaviours: physical
inactivity and overweight and obesity. In
2004–05, 9.4 million adults (68%) had at least
one of these two risk factors. Around 2.5
million adults (18%) were both physically
inactive as well as either overweight or obese.
As the number of risk factors a person has for
a particular condition increases, so does the
risk of developing that condition.11 Again,
while it is not possible to infer causality using
the NHS, adults who had at least one of these
two risk factors were, on average, more likely
to have certain conditions than those without
either of these risk factors. These conditions
include high blood pressure, Type II diabetes
and high cholesterol. Adults who were
classified as overweight or obese and
physically inactive were almost three times as
likely (2.9 times) to have Type II diabetes,
almost twice as likely to have high blood
pressure (1.9 times) and 1.5 times more likely
4 A B S • A U S T R A L I A N S O C I A L T R E N D S • 4 1 0 2 . 0 • 2 0 0 7
Overweight and obesity among
Aboriginal and Torres Strait Islander
adults
As with the NHS, height and weight measurements
were collected in the 2004–05 National Aboriginal
and Torres Strait Islander Health Survey (NATSIHS).
After adjusting for non-response, just over one-third
(35%) of Indigenous people aged 18 years and over
were recorded as being in the normal or healthy
weight range in 2004–05 based on BMI measures,
with a further 29% in the overweight category and
31% classified as obese. The proportion of
Indigenous adults in non-remote areas who were
overweight or obese in 1995 was 51% increasing to
60% in 2004–05.
When differences between the age structures of the
Indigenous and non-Indigenous populations are
taken into account, Indigenous adults were 1.2 times
more likely to be overweight or obese than
non-Indigenous adults. The disparity between
Indigenous and non-Indigenous rates of overweight
and obesity was greater for females than for males.12
(a) Based on self-reported height and weight.
(b) Denominator includes persons who considered
themselves underweight and persons who considered
themselves of acceptable weight.
Source: ABS 2004–05 National Health Survey.
Males Females
%
0
20
40
60
80 Overweight or obese(a)
Considered themselves overweight(b)
Perceptions of weight — 2004–05
to have Ischaemic heart disease than those
without either of these risk factors.
The relationship between health risk factors
and long term conditions is further reflected
in how people tend to rate their overall
health. In 2004–05, half (50%) of adults who
were either overweight or obese also rated
their health as excellent or very good, while
19% considered their health to be fair or
poor. This compares to 63% of adults in the
normal BMI category who considered
themselves to be in excellent or very good
health, and 12% who considered their overall
health to be fair or poor.
Endnotes
1 World Health Organisation 2003, Obesity and
Overweight: WHO Global Strategy on Diet,
Physical Activity and Health, WHO, Geneva.
2 Department of Health and Ageing 2002, About
Overweight and Obesity, DoHA, Canberra.
3 Access Economics 2006, The Economic Costs of
Obesity, Access Economics, Canberra.
4 Department of Health and Ageing 2006,
Australian better health initiative: Promoting
good health, prevention and early
intervention, DoHA, Canberra.
5 Australian Bureau of Statistics 1995, How
Australians Measure Up, cat. no. 4359.0, ABS,
Canberra.
6 Australian Institute of Health and Welfare 2004,
Australia's Health 2004, cat. no. AUS 44, AIHW,
Canberra.
7 Booth, M, Okely, AD, Denney-Wilson, E, Yang,
B, Hardy, L and Dobbins, T 2006, NSW Schools
Physical Activity and Nutrition Survey (SPANS)
2004, NSW Department of Health, Sydney.
8 King, T et al. 2005, 'Weight and place; a
multilevel cross sectional survey of area-level
disadvantage and overweight and obesity in
Australia' International Journal of Obesity,
pp 1–7, viewed 11 May 2007, <http://
www.kcwh.unimelb.edu.au/ viclanes/
weight_place_journal_article.pdf>.
9 Donath, S 2000, 'Who's overweight?
Comparison of the medical definition and
community views', Medical Journal of
Australia, vol.172, no. 8, pp. 375–377.
10 Australian Institute of Health and Welfare 2006,
Risk factors, viewed 24 April 2007, <http://
www.aihw.gov.au/nhpa/riskfactors/index.cfm>.
11 Australian Institute of Health and Welfare 2006,
Chronic Diseases and Associated Risk Factors
in Australia, 2006, cat. no. PHE 81, AIHW,
Canberra.
12 Australian Bureau of Statistics 2004–05 National
Aboriginal and Torres Strait Islander Health
Survey, ABS, Canberra.
 

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