Means and standard deviations of state measures.

Body checking is a common behavior in both the general population and individuals with body image disturbances. Cognitive-behavioral theories postulate that body checking reduces negative emotions in the short term, but over time contributes to the development and maintenance of eating disorder pathology. So far, few experimental studies have assessed these longer-term consequences, mostly under laboratory conditions, yielding inconsistent findings, and without considering individual vulnerability and specific personality traits. In a naturalistic experimental cross-over design, women with low (n = 76) vs. high (n = 103) body concern completed an online survey on trait characteristics (e.g., intolerance of uncertainty). After a two-day baseline to assess the daily amount of habitual body checking, participants underwent two three-day experimental conditions in randomized order, in which they were asked to exhibit typical vs. threefold increased body checking. Before and after conditions, participants completed state measures of eating disorder symptoms, body dissatisfaction, affect, and general pathology online. In women with high body concern, body image-related symptoms (i.e., drive for thinness, body dissatisfaction) and negative affect worsened in the increased body checking condition, whereas in the typical body checking condition, positive affect increased and no negative impact emerged. Conversely, women with low body concern remained unaffected, except for higher drive for thinness following the increased condition. Bulimic and depressive symptoms did not change in either group. The inclusion of intolerance of uncertainty from an exploratory perspective generally did not impact the results. Our findings regarding the high-risk group underscore the potential etiological relevance of body checking for body image disturbances and eating disorders. For individuals at risk and those already affected by eating disorders, it seems important to address individual body checking as early as possible within psychoeducation to prevent a presumably harmful increase in this behavior. Personality factors influencing vulnerability to body checking need to be further examined.