Original article
Severe obesity: Investigating the socio-demographics within the extremes of body mass index

https://doi.org/10.1016/j.orcp.2008.01.001Get rights and content

Summary

Objective

To examine the trends in the prevalence of classes I, II and III obesity between 1991 and 2006 among the South Australian adult population. In addition, to explore the association of severe (class II and III) obesity with a range of socio-demographics, chronic conditions and risk factor variables.

Method

Trends of self-reported obesity prevalence were examined using representative, annual, face-to-face South Australian Health Omnibus Surveys from 1991 to 2006 (n  3000 per year). Biomedical data, including measured height and weight, were collected in the North West Adelaide Health (cohort) Study (NWAHS), a representative random adult sample selected from the electronic white pages (EWP) (n = 4060).

Results

The age standardised prevalence of self-reported class II and III obesity among those aged 18 years and over increased from 2.4% in 1991 to 8.1% in 2006. The greatest relative percentage increase over this time was seen amongst those with class III obesity (452.3%). Using biomedical data, multivariate analysis results indicated that among those who were obese, women were more than two and a half times more likely than men to be of class II and III. Among those who were obese, those aged 20–54 years and living in the low/lowest quintiles of Socioeconomic Indexes for Areas, Index of Relative Socioeconomic Disadvantage (SEIFA IRSD) were statistically significantly more likely to be class II or III obese when compared to those in the highest categories.

Conclusion

The prevalence of class II and III obesity increased significantly between 1991 and 2006. The socio-demographics of those who are class II and III obesity are different from those that are normally described for obesity as a whole especially in regard to the younger age cohort. The current prevalence of severe obesity within Australia is probably underestimated and these results highlight the need to address this sub-group of the population.

Section snippets

Background

The increasing prevalence of obesity has been extensively reported in recent times and continues to place a burden on the public health system internationally and within Australia [1], [2], [3]. Reports of the dramatic end of the distribution, the proportion with class II and III obesity (often called severe or morbid obesity, defined as BMI  35) are relatively rare despite increases reported at twice the rate of obesity overall [4]. In South Australia, there have been similar increases in

The South Australian Health Omnibus Survey

The HOS is a user-pays survey co-ordinated by the Population Research and Outcome Studies Unit, South Australian Department of Health. These face-to-face household interview surveys of people aged 15 years and over (about n = 3000 people each year) have provided reliable estimates of self-reported height and weight since 1991 [15]. HOS is a representative population survey that involves a multistage, systematic, clustered area sample of people living in metropolitan Adelaide and country centres

Results

The age standardised prevalence of obesity in 1991 using HOS data was 11.1% (95% confidence interval (CI) 9.9–12.4) and was 27.2% (95% CI 25.3–29.1) in 2006 (χ2 trend = 1197.13, p  0.001). This represents a relative percentage increase of 144.8%. The prevalence of class II and III obesity combined increased from 2.4% (95% CI 1.8–3.0) in 1991 to 8.1% (95% CI 7.0–9.0) in 2006, a relative percentage increase of 241.2% (χ2 trend = 233.66, p  0.001). The prevalence of class III obesity increased from 0.6%

Discussion

This research has shown that there have been significant increases in the extreme classes of obesity over the last 16 years. In addition, women and lower socioeconomic groups and younger age groups (20–54 years) are more likely to be classified as having class II and III obesity when compared to class I. The increases within these classes are a progressively more crucial health care issue because of the associated morbidity and prevalence of related chronic conditions.

The strength in the NWAHS

Acknowledgements

The authors would like to acknowledge the contribution to the study by research, clinic and recruiting staff, and for the generosity of the NWAHS participants in the giving of their time and effort.

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