Original ArticlePrevalence of class-I, class-II and class-III obesity in Australian adults between 1995 and 2011–12
Introduction
The World Health Organisation defines three sub-classes of obesity severity (class-I body mass index (BMI): 30.0–34.9 kg/m2, class-II: 35.0–39.9 kg/m2 and class-III: ≥40.0 kg/m2) [1]. Severe obesity is defined as class-II or class-III obesity. We have previously reported that between 1980 and 2000, the prevalence of obesity (all classes) increased from 10.6 to 17.2% in men and 8.8 to 19.3% in women aged 25–65 in Australia [2]. Increases were greatest in the more severe obesity sub-classes. During this period, the prevalence of class-III obesity increased 4.8-fold in women and 2.5-fold in men, whilst comparable increases in class-I obesity were 1.8-fold and 1.5-fold respectively [2]. Similar observations were reported in other developed countries during the same period [3], [4], [5]. During the last decade, the prevalence of obesity has continued to increase. The Australian Bureau of Statistics report that 27.3% of Australians were obese (all classes) in 2011–12, an increase from 24.0% in 2007–08 [6]. To the best of our knowledge, recent obesity trends by severity sub-class have not been examined in Australia [2].
An exponential increase in the risk of adverse health outcomes is observed with increasing severity of obesity. For example, it has been estimated that the risk of developing type 2 diabetes is increased 93-fold in women and 42-fold in men who are severely obese, relative to healthy weight counterparts [7], [8]. Similarly, a body mass index greater than 40 is associated with between 6.5 and 13.7 years of life lost [9]. Consequently, small increases in the prevalence of severe obesity will probably have a similar impact on adverse health outcomes as large increases in the prevalence of class-I obesity. Therefore, understanding the composition of the obese population is critical to determining the associated morbidity and mortality burden of recent trends.
A socioeconomic gradient in obesity, where greater prevalence of obesity is observed in more disadvantaged groups, has been reported in most high income countries [10]. Two previous studies have reported a greater risk of severe obesity in more socioeconomically disadvantaged groups [11], [6]. However to the best of our knowledge, no previous study has explored differences in the prevalence of obesity classes I, II and III [1], across socioeconomic strata.
In the current study, we analysed nationally representative data to compare the prevalence of class-I, II and III obesity in Australian adults between 1995, 2007–08 and 2011–12. Obesity classifications were based on measured height and weight. We also examined the age, sex and socioeconomic profile for each obesity severity sub-class in 2011–12.
Section snippets
Data sources
Prevalence data for the population aged 18 years and over were sourced from customised data, provided for the purposes of this research, from the National Nutrition Survey (1995), the National Health Survey (2007–08), and the Australian Health Survey (2011–12) each conducted by the Australian Bureau of Statistics (ABS). Each survey was selected to provide a representative sample of the Australian population.
In 2011–12, a total of 30,721 households were approached to participate in the
Age and sex profile of the obese population in 2011/12
In 2011–12, the total prevalence of obesity was 27.2% (27.3% for males and 27.2% for females). In 2011–12, out of every 100 men, 19.4 were class-I obese, 5.9 were class-II obese and 2.0 were class III-obese (Table 1). Equivalent figures for women were 16.1, 6.9 and 4.2. Relative to men, women were 1.2- and 2.1-fold more likely to be class-II and class-III obese respectively. For men and women combined, one in every four people was obese, and one in every ten people was severely obese (Fig. 1).
Key findings
In the current study, we compared the prevalence of class-I, II and III obesity in Australian adults between 1995 and 2011–12. Nationally representative population samples were assessed and obesity classifications were based on measured height and weight. We observed that over the past two decades, the prevalence of all obesity sub-classes has increased, with the greatest relative growth in the more severe obesity sub-classes. In 2011–12, one in every four adults was obese and one in every ten
Disclosures
CK previously received an independent research grant from Allergan Australia (funding years 2010-11). EG, KB, CS, BS, MM, RC and AP declare have no relevant disclosures.
Funding support
This research was supported by an ARC Linkage grant (LP120100418) and an Australian National Preventive Health Agency grant (188PEE2011). EG was supported by an Australian Postgraduate Award. KB was supported by a Post-doctoral Research Fellowship from the National Heart Foundation of Australia (PH 12M 6824). AP was supported by a National Health and Medical Research Council Career Development Fellowship (1045456). CS was supported by an ARC Discovery Project grant (DP120103277). MM, BS, RC and
Acknowledgements
Thank-you to the Australian Bureau of Statistics for providing custom data analysed and for reviewing the methods section of the manuscript. Thank-you to Hasini Senadheera (work experience student visiting Baker IDI) for reviewing the manuscript.
References (25)
Increases in morbid obesity in the USA: 2000–2005
Public Health
(2007)- et al.
Bigger bodies: long-term trends and disparities in obesity and body-mass index among U.S. adults, 1960–2008
Soc Sci Med
(2012) - et al.
Adiposity measures as predictors of long-term physical disability
Annals Epidemiol
(2012) - et al.
The global obesity pandemic: shaped by global drivers and local environments
Lancet
(2011) - World Health Organisation, 2000. Obesity: preventing and managing the global epidemic (WHO Technical Report Series 894)...
- et al.
Trends in BMI of urban Australian adults, 1980–2000
Public Health Nutr
(2010) - et al.
Prevalence of class I, II and III obesity in Canada
CMAJ
(2006) - et al.
Shift in the composition of obesity in young adult men in Sweden over a third of a century
Int J Obes (Lond)
(2008) - et al.
Weight gain as a risk factor for clinical diabetes mellitus in women
Ann Intern Med
(1995) - et al.
Obesity, fat distribution, and weight gain as risk factors for clinical diabetes in men
Diabetes Care
(1994)
Association between Class III obesity (BMI of 40–59 kg/m2) and mortality: a pooled analysis of 20 prospective studies
PLoS Med
Social inequalities in obesity and overweight in 11 OECD countries
Eur J Public Health
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