To examine the impact of appearance comparison behaviours, trait body dissatisfaction and eating pathology on women's state body dissatisfaction and engagement in disordered eating behaviours in daily life.

Using ecological sampling method (ESM), 116 women residing in Australia, completed a baseline questionnaire containing the trait-based measures, before being signalled by an iPhone app six times daily, for seven days, to self-report on their recent appearance comparison behaviours, current state body dissatisfaction and recent disordered eating behaviours.

Multi-level modelling revealed that upward comparisons (comparisons against more attractive individuals) elicited increases in state body dissatisfaction (β=0.89, P<.001) and disordered eating behaviours (β=0.29, P=.002). Contrastingly, downward comparisons (comparisons against less attractive individuals) elicited decreases in state body dissatisfaction (β=–0.31, P=.048) and, unexpectedly, increases in disordered eating behaviours (β=0.46, P<.01). The frequency of appearance comparison engagement, regardless of whether it was upward or downward comparisons, was also predictive of increased disordered eating behaviours (β=0.12, P<.001). In addition, eating pathology and trait body dissatisfaction were directly associated with higher state body dissatisfaction, and increased in disordered eating behaviours (all P<.001).

These findings highlight the general negative impact that appearance comparisons have on fluctuating states of body dissatisfaction and eating pathology, as well as illustrating how trait characteristics partially account for this volatility. These findings provide further information that may be used to inform eating disorder prevention and intervention efforts.