Disordered eating behaviors (DEB) impact on health and wellbeing worldwide. This study aimed to examine sociodemographic trends in the prevalence of DEB over 20 years in the Australian general population.

Data were derived from five sequential cross-sectional surveys (1998, 2008, 2009, 2016 and 2017) with population-representative samples of adults and adolescents residing in South Australia (N = 15 075). DEBs investigated were objective binge eating (OBE), strict dieting/fasting, and purging. Sociodemographic data included gender, age, educational level, work and marital status, and residence.

OBE prevalence increased significantly. Strict dieting/fasting also increased from 1998 to 2008/9 but remained stable between 2008/9 and 2016/7. Purging prevalence did not change significantly over time. All survey years were associated with a significantly higher odds of OBE, and strict diet/fasting compared to 1998. Lower age, a higher Accessibility Remoteness Index of Australia (ARIA) score, higher body mass index (BMI), higher educational attainment, and not being in a married or de facto relationship were independently associated with greater adjusted odds for endorsing OBE. Younger age, female gender, and higher BMI were also independently associated with greater adjusted odds for endorsing strict dieting/fasting.

The increased prevalence of DEBs in various strata of Australian society has both public health and clinical implications. The results refute the stereotype that eating disorders (EDs) predominantly affect young women. They build impetus for future research on EDs among men and older individuals, with a view to developing tailored public health and clinical interventions for these populations.

Objective binge eating (OBE) and self-induced vomiting (SIV) occur and co-occur across a range of eating disorders but the extent to which the risk factors for these two behaviours overlap is unclear. Examination of this overlap was the focus of the current report.

A population of female Australian twins (n=1002), mean age 35 years (s.d.=2.11, range 28–40), participated in three waves of data collection and were assessed for lifetime disordered eating with a semi-structured interview at wave 3 and a self-report questionnaire at wave 1; risk factors were assessed via self-report at waves 1 and 3.

Non-shared environmental influences were the largest contributor to the variance of both OBE and SIV, with a more modest contribution of genetic influences. Between 5% and 14% of the environmental risk factors for OBE and SIV were shared and 27–100% of genetic risk factors were shared. SIV initiation was predicted by higher neuroticism and novelty seeking and lower maternal and paternal care, whilst lower levels of perceived paternal care, higher lifetime BMI, and a wider BMI range predicted OBE initiation. Retrospective correlates associated with both SIV and OBE onset were parental comments about weight, whilst higher levels of parental conflict, expectations and criticism was associated with OBE onset only.

The substantial extent of non-overlap between risk factors for SIV and OBE suggests that each of these behavioural disturbances warrants future investigation in its own right, not only when they occur in conjunction with each other.