We tested the hypothesis that the association between obesity and impairment in psychosocial functioning is mediated by levels of weight and shape concerns and/or binge-eating frequency. In the case of weight and shape concerns, the conditions for complete mediation were satisfied on each of 4 different measures of impairment. Further, obesity was associated with higher scores (indicating lower levels of impairment) on 2 of the 4 dependent variables, after weight and shape concerns were controlled. In the case of binge-eating frequency, and whereas the conditions for partial mediation were satisfied on each dependent measure, associations between obesity and functional impairment remained highly significant after binge frequency was controlled. Hence, in this study, participants’ levels of weight and shape concerns were a more potent mediator of the effect of obesity on psychosocial functioning than binge eating. These findings extend those of earlier studies suggesting that chronic physical ailments and/or pain mediate the association between obesity and impairment in psychosocial functioning (8, 9).
The finding that weight and shape concerns were a more potent mediator of the association between obesity and impairment in psychosocial functioning than binge eating is notable, since the significance of binge eating has been emphasized in both the obesity and eating disorders literature (2, 3). Recently, however, researchers in eating disorders have begun to focus on the clinical significance of weight and shape concerns among obese binge eaters (19, 43). In particular, it has been suggested that a diagnostic criterion reflecting the “undue influence of weight or shape on self-evaluation” may be as relevant for BED as it is for anorexia nervosa and bulimia nervosa (19, 24). Inclusion of the “undue influence” criterion for BED in future revisions of the DSM would be consistent with a “trans-diagnostic” view of eating disorders, in that the over-evaluation of weight or shape would be seen as a core diagnostic feature of all eating disorders (44).
If it is accepted that the improvement of quality of life is the ultimate goal of interventions for obesity (8), then identification of the specific variables that mediate the effect of obesity on quality of life has implications for the clinical management of individuals seeking treatment for weight loss. Currently, the focus of eating-disorder-based treatments for BED is on the stabilization of eating behavior, so that the effectiveness of treatment is measured primarily in terms of the reduction or cessation of binge eating (45). If, however, other aspects of eating disorder psychopathology are found to be more central to the obese patient's quality of life, then a focus on binge eating behavior may be counterproductive. With respect to the role of extreme weight or shape concerns in particular, because the presence of these concerns is not included in the criteria for BED suggested in DSM-IV, their significance in the treatment process may be overlooked. Both the stabilization of eating behavior and the improvement of body image are likely to be associated with improved quality of life among obese individuals who binge eat, irrespective of weight loss (19, 45). However, communication of the significance of body image dissatisfaction in terms of quality of life may be conducive to a greater focus on self-acceptance as a goal of treatment (46). Further research is needed to elucidate the potential benefits of incorporating a body-image component within obesity treatment programs (10).
Strengths, Limitations, and Other Considerations
There were several notable strengths of the present study. First, we were able to examine associations between obesity, eating-disordered behavior, and quality of life in a large and representative general population sample of women, thereby avoiding biases inherent in the use of treatment-seeking samples (16, 17). Second, inclusion of a comprehensive measure of eating disorder psychopathology permitted differentiation of the role of weight and shape concerns from that of binge-eating frequency. Third, several different measures of functional impairment were used. The fact that similarly robust findings were observed on all 4 measures lends credence to the findings. In addition, the fact that the inter-correlations between the different measures of impairment varied considerably suggests that these measures were not simply different measures of the same construct. Finally, we applied established statistical methods to directly test the hypothesis of mediation for each dependent variable.
There were also limitations of the present research. First, because measures of chronic medical illness and pain were not included in the Health and Well-Being Study, it was not possible to consider the relative importance of these and other potential covariates. Given the range of variables potentially contributing to impairment in psychosocial functioning, it is not surprising that the amount of variance explained by obesity and eating disorder features combined did not exceed 20% for any of the dependent variables. In this regard, it should be noted that aspects of eating disorder psychopathology not considered in the present study, such as levels of dietary restriction and eating concerns, might also be found to mediate the association between obesity and impairment in psychosocial functioning. Obesity is associated with a wide range of eating disorder features, all of which may make independent contributions to levels of general psychological distress (18). We focused on the roles of binge eating and weight and shape concerns because these features have received the most attention in the eating disorders literature and because there is good a priori evidence to support the roles of both (2).
Second, the use of a cross-sectional study design limits any inferences concerning the direction of the observed relationships. Although the findings support a role of eating disorder psychopathology in mediating the association between obesity and quality of life, it is likely that a prospective analysis would reveal reciprocal relationships between obesity, eating-disordered behavior, and quality of life (47, 48).
Third, only generic measures of functional impairment were included. The advantage of these measures is that they permit comparison of the effects of different disease states on quality of life, whereas disease-specific measures are likely to be more sensitive to the effects of a given condition on specific aspects of functioning (15, 17).
Fourth, we considered only one possible definition of obesity, namely, a BMI of ≥30 kg/m2. We acknowledge that different results might have been obtained with a different threshold. It would be of interest to test this hypothesis in future research.
Finally, it should be reiterated that approximately 40% of individuals selected to participate at the first phase of the study chose not to return a completed questionnaire. Although a detailed analysis of data from a pilot study found no evidence for the existence of response bias on any of the study measures (27), differences between respondents and non-respondents on unmeasured characteristics cannot be excluded.
Interpretation of the present findings is necessarily limited to the associations between obesity, eating-disordered behavior, and quality of life in women. Because eating-disordered behavior is likely to be experienced differently by men and women (14), associations between obesity, eating-disordered behavior, and quality of life are also likely to differ for men and women. For example, evidence suggests that binge eating is not associated with the same high levels of distress in men as in women (49). This finding likely reflects, at least in part, the fact that the prevalence of extreme weight and shape concerns is lower in men (3, 50). Similarly, gender differences in the prevalence of weight and shape concerns and/or the way in which these concerns are experienced, may account for the finding, reported in some community-based studies, that obesity is associated with elevated levels of anxiety and depression in women, but not in men (51, 52). Gender-specific associations between overweight and impairment in psychosocial functioning, as well as other adverse outcomes, such as attention and behavior problems, also have been reported in general population samples of children and adolescents (53, 54). It has been suggested that these findings may reflect higher levels of body image dissatisfaction and/or a greater susceptibility to weight-related teasing in girls than in boys (53, 54).
Interestingly, in the present study, obesity was associated with lower levels of impairment on 2 of the 4 dependent variables, namely, the SF-12 MCS and the Psychological Health subscale of the WHOQOL-BREF, after weight and shape concerns were included in the regression models. Although this finding awaits replication in a different sample, it is possible that young adult women who are overweight but who have low levels of weight and shape concerns constitute a subgroup who function at above-average levels when compared with the population of young adult women as a whole, at least in the specific aspects of functioning assessed by the SF-12 and WHOQOL-BREF. It may be that future research will identify characteristics of obese women that are conducive to better mental health, the effects of which are more apparent among subgroups of individuals with low levels of weight or shape concerns.
Finally, it should be noted that the role of “body image dissatisfaction” or “weight and shape concerns” in mediating the association between obesity and impairment in psychosocial functioning is likely to depend on the way in which these terms are operationalized. In the eating disorder literature, there has been some confusion concerning how best to conceptualize and, in turn, assess the disturbance in body image that is characteristic of eating disorder patients (24). Findings from recent studies suggest that there is a need to distinguish between the over-evaluation of weight or shape and the more general construct of “body image dissatisfaction” (43, 55, 56). In the present study, weight and shape concerns were assessed using the full subset of items of the EDE-Q Weight Concern and Shape Concern subscales, as opposed to the specific items addressing the over-evaluation of weight or shape (24). In practice, there is no clear separation between “normative” weight or shape concerns and “over-evaluation” of weight or shape, and this boundary may be particularly problematic in obese individuals (46).
In summary, we found, in a community sample of young adult women, that levels of weight and shape concerns were a potent mediator of the association between obesity and impairment in psychosocial functioning, whereas the role of binge-eating frequency was much less pronounced. These findings support a greater focus on body acceptance in obesity treatment programs.