The role of loss of control eating in purging disorder.

Purging disorder (PD) is an Other Specified Feeding or Eating Disorder characterized by “recurrent purging behavior to influence weight or shape… in the absence of binge eating.”1 The absence of a low body weight distinguishes PD from anorexia nervosa, and the absence of binge-eating episodes distinguishes PD from bulimia nervosa (BN). In the DSM, binge eating is defined by discrete episodes of loss of control (LOC) eating involving the consumption of an unusually large amount of food given context and time (usually two hours).1 LOC eating can be described as feeling unable to stop eating, as though eating were not preventable, or inevitable.2 By definition, women with PD do not have binge episodes; however, women with PD may experience a sense of LOC while consuming an amount of food that is not unusually large. These LOC eating episodes are called subjective binge episodes, contrasting them from the objectively large binge episodes as defined within the DSM. Research studies have varied in requiring3, excluding4,5 or not mentioning LOC eating in definitions of PD,6-8 making it unclear if LOC eating is related to the clinical presentation of PD. This study sought to evaluate the clinical significance of LOC eating in PD because this may have important implications for how PD should be defined within future editions of the DSM. Across eating disorders, LOC eating includes both subjective and objective binge episodes and is associated with psychopathology and impairment in both community and clinical samples.9-12 Adults with LOC eating report greater eating pathology and general psychopathology than adults without LOC eating.12 Individuals with LOC eating experience greater impulsivity,13 anxiety,11 and depressive symptoms9,11 than those without LOC eating. Additionally, LOC eating is associated with a poorer quality of life.10,14 Based on these findings, LOC eating may be an important clinical feature of PD. However, prior studies of LOC eating across eating disorders do not distinguish the proportions of LOC eating episodes that are objective versus subjective binge episodes, given that LOC eating can include a range in amount of food consumed. Thus, it is uncertain if prior findings apply to LOC eating in PD in which LOC eating is constrained to an amount of food that is not more than what most people would eat. To address this ambiguity, some prior work has directly examined the role of LOC eating in PD.15-17 In one study of PD, those with LOC eating reported more restraint, eating concern, shape concern, and weight concern than those without LOC eating.17 Additionally, the PD group with LOC eating reported more cognitive impairment and psychological distress than the PD group without LOC eating.17 These findings suggest that LOC eating is associated with a greater severity of illness. However, this sample included women who used purging and nonpurging (i.e., fasting, excessive exercise) compensatory methods, and analyses did not control for purging method or purging frequency. Therefore, this group was broader and more inclusive than PD as defined in the DSM,1 and differences attributed to LOC eating were potentially confounded by an association between LOC eating and use of purging (versus nonpurging) methods or purging frequency. As LOC eating and purging frequencies are correlated,12,18 increased purging, rather than LOC eating frequency, may explain the observed associations. Other work by Mond and colleagues, in which PD was restricted to those who used purging methods, did not find differences between PD with LOC eating and PD without LOC eating,16 suggesting LOC eating may have no effect on the severity of illness when purging methods are held constant. Finally, Brown and colleagues15 found that the frequency of LOC eating in PD was associated with Cluster B personality symptomatology and trait anxiety.15 However, like the studies by Mond and colleagues,16,17 Brown et al.15 did not control for purging frequency when examining associations between LOC eating frequency and personality features. Overall, examination of associations between LOC eating and clinical presentation of PD are inconclusive due to a lack of control for possible confounds. The current study sought to address the importance of LOC eating in the clinical presentation of PD by examining the relationship between LOC eating frequency and measures of eating pathology, related psychopathology, personality, distress and impairment. To distinguish between correlates of LOC eating episodes and correlates of purging or other key covariates, significant bivariate associations were followed by multivariate models that controlled for key covariates, including purging frequency. Given discrepant findings and the limited literature on LOC eating in PD 15-17, we did not form a priori hypotheses regarding associations. Instead, exploratory analyses provide much needed data on the role of LOC eating in PD. If LOC eating is associated with eating pathology, related psychopathology, personality, and distress and impairment, LOC eating should be considered in defining the syndrome.