This study investigated the prognostic significance of preoperative and postoperative loss of control over eating in extremely obese bariatric surgery patients over 24 months of prospective multi-wave follow-up. Prior to surgery, 61% of surgical patients reported LOC over eating, which is comparable to reports from other research groups utilizing similar assessment procedures (see 52
for a review). Preoperative LOC was associated concurrently with significantly elevated eating-disorder psychopathology and psychosocial difficulties and predicted prospectively postoperative LOC. Preoperative LOC, however, was unrelated to postoperative weight loss or psychosocial functioning. In contrast, LOC following
surgery was a negative prognostic indicator for weight loss, with postoperative LOC predicting less weight loss at 12- and 24-month follow-up points. The influence of postoperative LOC became more pronounced as the time post-surgery increased, and may correspond with the weight-loss plateau that occurs some years following surgery 2, 53
. Further, the rates of LOC increased over the course of the study: at 6 month follow-up, approximately 31% of the sample reported LOC, and by the 24 month follow-up this percentage had increased to 39% overall, and to nearly 50% among those experiencing LOC prior to surgery. The group reporting postoperative LOC reported elevated depressive symptoms and eating disturbances, as well as lower levels of quality of life as measured by the Mental Components summary scale of the SF-36. Of note, LOC was not predictive of the Physical Component summary scale, suggesting that the significant physical improvements attained through bariatric surgery are not easily influenced by a subjective sense of loss of control. On the other hand, LOC does predict important bariatric outcomes such as eating-specific and broad psychosocial functioning in addition to weight loss.
The current findings add to the emerging literature showing considerable improvements following bariatric surgery, both in terms of weight loss and psychosocial outcomes through 24-months post-surgery. A substantial percentage of patients, however, begins to plateau by 12 to 24 months post-surgery and may experience weight regain 54
. In the current study, through 24-months of post-surgical follow-up, LOC following surgery was significantly associated with weight regain at subsequent assessment points. Collectively, research investigating pre-surgical psychosocial, historical, and even eating-specific factors has reported little impact on post-surgical outcomes 3, 5, 55
. This is a limitation, since identification of such characteristics would suggest the need for supplemental treatments to ensure maximum treatment benefit. Therefore our inclusion of both pre-surgical and post-surgical
problematic eating marks one of the first studies to prospectively identify patient-specific factors predicting a worsened clinical profile, and identifies a potential area for clinical intervention.
Our results support and extend findings from previous research reporting that preoperative binge eating and/or loss of control over eating does not impede weight loss 11, 17, 21–24
. Collectively this research indicates that preoperative binge eating, although common 52
, may not require specific additional clinical intervention before treatment. Our results, however, do suggest that the emergence of post-operative
eating problems has negative prognostic influence on weight loss outcomes, as well as some of the psychosocial benefits associated with surgery. The current study parallels previous research with other patient groups 29–31
identifying the clinical significance of LOC over eating as a correlate of eating-specific and more global psychopathology. Therefore post-surgical LOC over eating, although subclinical in nature, should be the target of clinical intervention following surgery. Given that nearly 40% of the patients in this study reported LOC over eating in the 24 months following surgery, these findings also suggest that a substantial proportion of bariatric surgery patients may benefit from continued clinical care. Specifically, the subjective sense of a loss of control over eating has significant impact on weight and psychosocial outcomes, independent of the amount of food that is consumed. Clinicians working with this patient group should be aware that various aspects of eating disturbance are more clinically relevant than the mere amount of food consumed. In terms of identifying patients at risk for psychosocial difficulties or distress, LOC is a good proxy or marker for identifying those patients who may benefit from more clinical attention to manage their distress. Clinicians can readily assess whether a patient experiences subjective LOC over eating episodes based on verbal report. Further, clinicians should be aware that while the mere presence or absence of LOC following surgery predicts weight outcomes, a graded effect exists such that the frequency of LOC predicts worsened psychosocial outcomes. An apt focus of clinical attention would be on developing coping strategies or on cognitive restructuring adapted from the best-established treatments for eating disorders 56
. Future research will be required to identify the best treatments to ensure weight maintenance or continued losses in the years following surgery.
This study has some potential limitations that should be considered when interpreting the findings. The findings pertain to extremely obese patients who seek bariatric surgery at an urban general medical center and undergo gastric bypass procedures. The findings may not generalize to less obese patients or to obese patients who seek different (non-surgical) forms of treatment or different forms of bariatric surgeries. Although the questionnaire we used to assess LOC elicits specific estimates in terms of the number of eating episodes in which LOC was experienced, self-report measures are potentially limited by retrospective recall and response biases. Previous psychometric evaluations have found that the EDE-Q may overestimate certain aspects of eating pathology relative to clinician interview 42, 57
, so it is possible that the rates of LOC were over-reported. Alternatively, some research suggests that patients are more candid when reporting symptoms in questionnaire format than in clinician interview 58
. Our reliance on self-reported weights is an additional limitation, however research has found that self-reported weight is an adequate proxy for measured weights 59, 60
. Since we were primarily interested in time-varying outcomes, however, we opted to employ self-reported data corresponding with the time of assessment rather than measured weights taken at a different time-point. The findings are further limited by the amount of missing data, particularly for the 24-month follow-up point, although the use of mixed models analyses permitted use of all available data for all participants, and these models offer important advantages over other methods of imputation for missing data in longitudinal research 61
. However, it should be noted that our analyses on the rate of dropout found few differences between participants who provided data at the follow-up points compared to those who did not; participants providing follow-up data at 24 months did not differ from those who did not on any outcome variable measured at 12 months.
Another potential limitation is the possibility that extremely obese patients seeking bariatric surgery may minimize the existence of certain problems (e.g., distress level, binge eating) in order to appear psychologically healthy and appropriate for the surgery. Indeed, research has shown that patients undergoing psychological evaluation prior to surgery have elevated scores on social desirability and commonly deny active problems 62
. Although this possibility must be considered, the research study procedures and informed consent methods should have served to minimize this likelihood. Specifically, participants completed the assessments as part of a research study and were informed that the results would not be shared with the clinical treatment team unless the patients specifically requested it. It was stressed that the assessments would have no medical benefit to patients, and were intended solely to advance knowledge regarding psychosocial needs and outcomes of bariatric surgery patients. Further, LOC predicted emotional and psychological outcomes, but not physical domains, which suggests that response sets were not responsible for the pattern of results. Finally, since baseline prevalence of LOC was much higher than prevalence of LOC post-surgery, the possibility that patients minimized problems prior to surgery is unlikely.
In summary, this study examined pre-operative and post-operative loss of control over eating in relation to 6-, 12-, and 24-month postoperative outcomes in gastric bypass patients. The findings suggest that preoperative LOC does not appear to be a negative prognostic indicator for gastric bypass surgery. However, postoperative LOC does appear to impede the rate of weight loss, particularly as the time-since-surgery increases. Similarly, postoperative LOC predicts psychosocial outcomes, including depressive symptoms, additional eating disturbances, and some aspects of quality of life. Therefore postoperative LOC over eating is a useful indicator of attenuated post-surgical improvements and may warrant clinical focus in post-surgical care. Longer-term follow-up is needed to determine the durability of these outcomes.