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

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.
(© Crown Copyright 2008 Published by Elsevier Ltd on behalf of Asia Oceania Assoc. for the Study of Obesity. All rights reserved.)