Prevalence of class-I, class-II and class-III obesity in Australian adults between 1995 and 2011–12

doi:10.1016/j.orcp.2015.02.004

Obesity Research & Clinical Practice

Volume 9, Issue 6, November–December 2015, Pages 553-562

https://doi.org/10.1016/j.orcp.2015.02.004 Get rights and content

Summary

Objective

To compare the prevalence of class-I, II and III obesity in Australian adults between 1995, 2007–08 and 2011–12.

Methods

Prevalence data for adults (aged 18+ years) were sourced from customised data from the nationally representative National Nutrition Survey (1995), the National Health Survey (2007–08), and the Australian Health Survey (2011–12) conducted by the Australian Bureau of Statistics. Obesity classifications were based on measured height and weight (class-I body mass index: 30.0–34.9 kg/m², class-II: 35.0–39.9 kg/m² and class-III: ≥40.0 kg/m²). Severe obesity was defined as class-II or class-III obesity.

Results

Between 1995 and 2011–12, the prevalence of obesity (all classes combined) increased from 19.1% to 27.2%. During this 17 year period, relative increases in class I, II and III obesity were 1.3, 1.7 and 2.2-fold respectively. In 2011–12, the prevalence of class I, II and III obesity was 19.4, 5.9 and 2.0 per cent respectively in men, and 16.1, 6.9 and 4.2 per cent respectively in women. One in every ten people was severely obese, increasing from one in twenty in 1995, and women were disproportionally represented in this population. Obesity prevalence increased with increasing levels of area-level socioeconomic disadvantage, particularly for the more severely obese classes. Severe obesity affected 6.2% and 13.4% in the least and most disadvantaged quintiles respectively.

Conclusion

Over the last two decades, there have been substantial increases in the prevalence of obesity, particularly the more severe levels of obesity. This study highlights high risk groups who warrant targeted weight gain prevention interventions.

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.

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Original ArticlePrevalence of class-I, class-II and class-III obesity in Australian adults between 1995 and 2011–12

Summary

Objective

Methods

Results

Conclusion

Introduction

Section snippets

Data sources

Age and sex profile of the obese population in 2011/12

Key findings

Disclosures

Funding support

Acknowledgements

Public Health

Soc Sci Med

Annals Epidemiol

Lancet

Trends in BMI of urban Australian adults, 1980–2000

Public Health Nutr

Prevalence of class I, II and III obesity in Canada

CMAJ

Shift in the composition of obesity in young adult men in Sweden over a third of a century

Int J Obes (Lond)

Weight gain as a risk factor for clinical diabetes mellitus in women

Ann Intern Med

Obesity, fat distribution, and weight gain as risk factors for clinical diabetes in men

Diabetes Care

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

Original Article
Prevalence of class-I, class-II and class-III obesity in Australian adults between 1995 and 2011–12

Association between Class III obesity (BMI of 40–59 kg/m²) and mortality: a pooled analysis of 20 prospective studies