Psychological predictors of weight loss after bariatric surgery: A review

ORCP-337; No. of Pages 15

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Obesity Research & Clinical Practice (2013) xxx, xxx.e1—xxx.e15

REVIEW

Psychological predictors of weight loss after bariatric surgery: A review of the recent research Cathrine L. Wimmelmann a,∗, Flemming Dela b,c, Erik L. Mortensen a,c a

Section of Environmental Health, Department of Public Health, University of Copenhagen, Copenhagen, Denmark b Systems Biology Research Section, Department of Biomedical Sciences, University of Copenhagen, Copenhagen, Denmark c Center for Healthy Aging, Faculty of Health and Medical Sciences, University of Copenhagen, Denmark Received 13 May 2013 ; received in revised form 9 September 2013; accepted 16 September 2013

KEYWORDS Bariatric surgery; Obesity; Psychological predictors; Mental health; Weight loss

Summary Background: Morbid obesity is the fastest growing BMI group in the U.S. and the prevalence of morbid obesity worldwide has never been higher. Bariatric surgery is the most effective treatment for severe forms of obesity especially with regard to a sustained long-term weight loss. Psychological factors are thought to play an important role for maintaining the surgical weight loss. However, results from prior research examining preoperative psychological predictors of weight loss outcome are inconsistent. The aim of this article was to review more recent literature on psychological predictors of surgical weight loss. Methods: We searched PubMed, PsycInfo and Web of Science, for original prospective studies with a sample size >30 and at least one year follow-up, using a combination of search terms such as ‘bariatric surgery’, ‘morbid obesity’, ‘psychological predictors’, and ‘weight loss’. Only studies published after 2003 were included. Results: 19 eligible studies were identified. Psychological predictors of surgical weight loss investigated in the reviewed studies include cognitive function, personality, psychiatric disorder, and eating behaviour.

∗

Corresponding author at: Section of Environmental Health, Department of Public Health, University of Copenhagen, Øster Farimagsgade 5, Building 5, 1st Floor, 1353 Copenhagen K, Denmark. Tel.: +45 35 32 74 86. E-mail addresses: [email protected], [email protected] (C.L. Wimmelmann). 1871-403X/$ — see front matter © 2013 Published by Elsevier Ltd on behalf of Asia Oceania Assoc. for the Study of Obesity.

http://dx.doi.org/10.1016/j.orcp.2013.09.003

Please cite this article in press as: Wimmelmann CL, et al. Psychological predictors of weight loss after bariatric surgery: A review of the recent research. Obes Res Clin Pract (2013), http://dx.doi.org/10.1016/j.orcp.2013.09.003


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C.L. Wimmelmann et al. Conclusion: In general, recent research remains inconsistent, but the findings suggest that pre-surgical cognitive function, personality, mental health, composite psychological variables and binge eating may predict post-surgical weight loss to the extent that these factors influence post-operative eating behaviour. © 2013 Published by Elsevier Ltd on behalf of Asia Oceania Assoc. for the Study of Obesity.

Contents Introduction.................................................................................................. Method....................................................................................................... Pre-surgical psychological evaluation of bariatric candidates ............................................ Results ....................................................................................................... Predictors of outcome ................................................................................... Pre-surgical BMI ......................................................................................... Demographic factors..................................................................................... Cognitive function ....................................................................................... Personality .............................................................................................. Psychopathology......................................................................................... Binge eating disorder and eating behaviour.............................................................. Multiple predictors ...................................................................................... Long-term weight outcome .............................................................................. Conclusion ................................................................................................... References ...................................................................................................

Introduction Obesity is a substantial public health problem worldwide. The prevalence of obesity has increased dramatically over the last three decades [1—3] with the most marked increase in more severe forms of obesity [4]. This is alarming considering that overweight and particularly morbid obesity, defined as Body Mass Index (BMI) ≥ 40 kg/m2 , is associated with a marked increase in mortality [5] often caused by medical co-morbidities, such as diabetes, cardio-vascular disease, and cancer [6,7]. In addition, psychological and social complications as well as impaired health-related quality of life (HRQOL) are prevalent among obese patients [8,9]. Traditional weight loss strategies, such as behavioural therapy, low-caloric diets and pharmacological treatment, have shown good results for obesity class I and II (BMI 30—34.9 and 35—39.9 kg/m2 , respectively) [10], but are usually ineffective in the long-term treatment of morbid obesity [11—13]. Most patients who present for bariatric surgery have already been unsuccessful in multiple attempts to achieve a sustained weight loss through non-surgical treatment programmes. Despite potential postoperative complications, such as gastric dumping syndrome, incisional hernia, and infections, bariatric surgery

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is currently considered the treatment of choice for these patients and may result in weight loss of up to 80% of the excess body weight with subsequent reductions in medical risk factors, obesity-related co-morbidities, and psychological symptoms [14—16]. However, bariatric surgery should be considered a ‘stepping stone’, and patients must be prepared to engage in comprehensive lifestyle changes. The generally positive results of bariatric treatment have been questioned by recent studies reporting that a substantial minority of bariatric patients have suboptimal weight loss often defined as less than 40—50% excess weight loss (EWL) for Gastric Bypass (GBP) [17,18]. In addition, up to 20—30% of bariatric patients undergoing obesity surgery regain some if not all of their initial weight loss around 2 years after surgery [19—22]. Non-surgical and psychological factors that affect the patients’ ability to adjust to the postoperative situation are likely to be involved in the course of this regain [23—25]. However, no presurgical psychological predictors have consistently been demonstrated [26,27]. Identifying potential indicators of surgical success will not only enable better patient selection, but may also contribute to the improvement of treatment by facilitating the development of pre- and post-operative psychosocial interventions.



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Psychological predictors of surgical weight loss Generally, a successful outcome of obesity surgery involves three main goals: weight loss, improvements in HRQOL, and reduction of obesityrelated comorbidities. The aim of this article is to review results from studies examining predictors of postoperative weight loss. Improvement of obesityrelated comorbidities is assumed to depend on postoperative weight loss and will not be discussed here. According to a recent systematic review [26], the existing literature about potential predictors of success after bariatric surgery is far from conclusive. Herpertz and colleagues [26] summarised the results from studies conducted between 1980 and 2002. The overall conclusion of this review was that personality traits and psychiatric comorbidity do not seem to have predictive value for surgical weight loss. However, the authors suggested that severe psychiatric disorders including personality disorders may be a negative predictor of weight loss. Furthermore, depressive and anxiety symptoms directly related to obesity appeared to predict larger postsurgical weight loss. Thus, Herpertz et al. [26] emphasised that the severity of symptoms is more relevant for weight loss outcome than the specific character of the symptoms. These conclusions were supported by a review conducted by Van Hout et al. [27]. In the current article, we review results published more recently (2003—2012) and compare this research to previously published results.

Method To identify relevant articles, we searched Pubmed, PsycInfo and Web of Science using combinations of search terms such as ‘‘Obesity’’, ‘‘Obesity surgery’’, ‘‘Bariatric surgery’’, ‘‘weight loss’’, ‘‘Predictors’’, ‘‘Psychological’’, ‘‘Psychiatric’’, ‘‘Psychosocial’’, and ‘‘Surgical outcome’’. Initially, titles of the identified studies were screened and abstracts of the relevant studies were read. Furthermore, reference lists were checked for relevant studies. The remaining eligible studies were read in detail. Only original prospective studies published between 2003 and 2012 with a sample size of >30 patients were considered. Statistical power considerations lead to this cut-off for minimum sample size since smaller samples typically will have insufficient power while it is also important not to exclude relevant studies with relatively small samples. In addition, a minimum of one year follow-up was chosen as an inclusion criterion as the impact of surgery on weight loss may reduce the impact of psychological factors during the first

xxx.e3 postoperative months. The surgical effect usually begins to abate one year postoperatively, and the influence of psychological factors may therefore become more evident with long-term follow-ups. The current review focused on psychological predictors of surgical weight loss. Studies investigating potential non-psychological predictors, such as medical co-morbidities, were therefore not considered. Furthermore, child/adolescent studies were not included, given that bariatric surgery has most commonly been performed in adults, and age at time of surgery has been shown to affect surgical outcome [27,28]. We included studies using both restrictive (e.g. gastric banding, GB) and combined restrictivemalabsorptive procedures (e.g. gastric bypass, GBP). It should be emphasised that postoperative weight loss varies between these surgical procedures, with greater weight loss occurring in patients undergoing GBP. Nevertheless, results from studies of different surgical procedures are combined throughout the rest of this review.

Pre-surgical psychological evaluation of bariatric candidates The psychological and psychiatric profiles of bariatric candidates have been reviewed extensively elsewhere [9,27,29,30] and will therefore only be shortly addressed here. Morbidly obese individuals are quite heterogeneous with regard to psychological characteristics [27]. Bariatric patients tend to have higher scores on certain personality traits, such as neuroticism, harm avoidance, impulsiveness, and low self-esteem, compared with the general population [31]. In addition, bariatric patients often report poorer body image and marked impairments in HRQOL compared with both obese participants in traditional weight loss treatment and normal weight controls [9,32]. It remains an open question whether these findings primarily indicate that the most severe forms of obesity often cause significant psychological distress or rather reflect that individuals with severe distress are more likely to seek surgical treatment. Using diagnostic interviews to assess preoperative psychiatric status of bariatric patients, recent studies have consistently demonstrated that 20—60% have a current psychiatric disorder, such as depression or an anxiety disorder [33—37], and a lifetime history of psychiatric disorders has been reported in up to 73% [34,38]. Furthermore, personality disorders are observed in up to 72% of morbidly obese individuals seeking bariatric surgery [38,39]. The greatest risk of co-morbid psychiatric



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xxx.e4 conditions has been found in patients with binge eating disorder (BED) [40,41] and especially in patients with the most severe obesity [33,42]. In most countries, current guidelines for patient selection permit only patients with BMI >40 kg/m2 or patients with BMI ≥35 kg/m2 and with specific medical comorbidities to undergo bariatric surgery.

Results Predictors of outcome In this review of predictors of weight loss after bariatric surgery, we identified 19 articles published after 2003 that explicitly investigated the predictive value of psychological factors. The investigated predictors of surgical weight loss included cognitive function [43], certain personality traits [31,44—46], mental and psychiatric status [37,47—52], and eating behaviour, including BED [53—59]. In addition, pre-surgical weight loss [60,61] and several demographic factors were identified as potential predictors in prospective studies. Some limitations of the literature should be mentioned. First of all, not all studies specify the strength of the reported associations between investigated psychological predictors and weight loss outcome. In general, the effect sizes are small to moderate [31,48,49,51], and individual psychological predictors have been reported to explain 19.5% [56] to 40% [45] of the variance in postoperative % weight loss and BMI reduction, respectively. In addition, some of the included studies were conducted with relatively short follow-up periods, were based on small sample sizes, used self-report instruments, or have other methodological limitations. Consequently, the extent to which variation in the reported results reflects methodological differences should be considered when interpreting the results of the included studies, which are listed in Table 1.

Pre-surgical BMI Several studies have investigated whether presurgical BMI is of prognostic value for the postoperative outcome. Results are highly inconsistent, with some studies suggesting a negative relationship between baseline BMI and short-term weight loss [46,60], some a positive relationship [31], and some no relationship [50]. In contrast, pre-surgical weight loss has consistently been found to predict greater weight loss following surgery [61,62]. Most bariatric clinics require surgery candidates to lose a minimum of 8—12% of their body

C.L. Wimmelmann et al. weight to be accepted for surgery. To achieve a relatively large rapid weight loss before surgery is important both for technical surgical reasons and for behavioural reasons, as it demonstrates that the patient is able to adhere to an extremely strict diet, which is an essential behavioural demand after surgery. The largest study to date investigating the effects of pre-surgical weight loss on postoperative outcome indicated that preoperative weight loss impacted both perioperative length of admission and weight loss after operation [61]. Among 884 patients, those who lost at least 10% of their excess body weight prior to surgery were twice as likely to achieve a 70% EWL after surgery. This result suggests that the requirement of weight loss before surgery can help health professionals identify the bariatric candidates most likely to comply with the postoperative behavioural demands and achieve the greatest weight loss.

Demographic factors With regard to demographic factors, previous research has indicated that success following obesity surgery is more likely to occur in young female patients with high socioeconomic status [27]. In a large cross-sectional study with 7540 patients, age, height, weight, and surgical procedure explained 40—50% of the variance in weight loss after surgery [63], emphasising a substantial contribution of demographic and non-psychological factors to postoperative weight loss. The majority of studies published since 2003 have reported that age is a significant predictor of weight loss after surgery, with greater weight loss occurring in younger patients [28,64]. Prior to surgery, younger patients typically present with fewer comorbidities and increased mobility [65,66], which could explain the larger weight loss outcome compared with older patients. In contrast, some studies [46,50] have found that age did not affect weight loss; one study even reported that older patients had a greater %EWL compared with younger patients [60], but this result may reflect that the study did not take BMI into account. In addition, older patients in this study sample tended to have more follow-up visits than younger patients, suggesting that the result may be mediated by number of follow-up visits. In previous research, women have consistently been found to have greater postsurgical weight loss compared with men [27]. Recent results regarding the predictive value of sex are more conflicting. For instance, Chau et al. [60] found that female GB patients demonstrated less % EWL compared with men, which may reflect gender-related eating habits. The authors speculated that, compared


Number of patients

Assessment methods

Follow-up

Pre-surgical measures

Predictor of postoperative weight outcome

Spitznagel et al. [43]

84

12 months

Cognitive function

Canetti et al. [44]

44 in surgery group, 47 in diet group

Standardised questionnaires and computer-based cognitive battery Standardised questionnaires and self-made questionnaires

12 months

Larsen et al. [31] De Panfilis et al. [45]

168 35

Standardised questionnaires Structured clinical interviews and standardised questionnaires

>2 years 12 months

Pontiroli et al. [46]

172

Clinical interviews

>12 months

Social support Motivation for control Sense of control Self-esteem Neuroticism Fear of intimacy Emotional eating Personality Mental health Personality Depression Anxiety Eating disorders Mental health Personality disorders

Attention/executive function Memory Emotional eating

De Zwaan et al. [37]

107

Structured clinical interviews

24—36 months

Mental health

Dixon et al. [47]

262

Standardised questionnaires

12 months

Lanyon et al. [48]

131

Structured interviews, standardised questionnaires and self-made questionnaires

12.8 months

Depression HRQOL Appearance orientation Sleepiness Psychopathology Personality Depression Binge eating

Lanyon et al. [49]

131

Structured interviews, standardised questionnaires and self-made questionnaires

1—3 years

Compliance Attendance Narcissistic personality Anxiety disorders Anxiety + depressive disorders —

Combination of 4 composite variables (Medical health, Mental health, Interpersonal support, Eating behaviour) Self-confidence Support Total coping skills

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Psychopathology Personality Depression Binge eating

Egoism score Persistence score

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Referencea


Effect of pre-surgical psychological and psychosocial factors on weight loss.

Psychological predictors of surgical weight loss


Table 1

Number of patients

Assessment methods

Follow-up

Pre-surgical measures

Predictor of postoperative weight outcome

Kinzl et al. [50]

140

Structured clinical interviews, semi-structured interviews and self-made questionnaires

30—84 months

>2 psychiatric disorders Eating disorder

Legenbauer et al. [51]

153 (surgery group), 250 (diet group), 128 (obese controls) 153 (surgery group), 250 (diet group)

Structured psychiatric interviews, structured interview Structured psychiatric interviews, structured interview Standardised questionnaires

4 years

Mental health Eating disorders Sociodemographic factors Childhood experiences Sexuality Mental health Binge eating behaviour

4 years

Mental health Binge eating behaviour

Depression Anxiety

1—6 years

—

Clinical interviews and standardised questionnaires

12 months

Binge eating Depression HRQOL Binge episodes Eating behaviour

Structured interviews and standardised questionnaires Semi-structured clinical interviews, standardised questionnaires, and self-made questionnaires

>12 months

Eating pathology Eating behaviour BED NES Grazing Eating behaviour Depression HRQOL Depression Body image Anxiety Binge eating Eating disorders Depression Body image Self-esteem Eating psychopathology Loss of control Depression HRQOL

—

Legenbauer et al. [52]

Wadden et al. [54]

Burgmer et al. [55]

59 (NBE surgery group), 36 (BED surgery group), 49 (BED diet group) 149

Colles et al. [56]

129

Sallet et al. [57]

216

Structured clinical interviews and standardised questionnaires

2 years

White et al. [58]

139


12 months

White et al. [59]

361


2 years

a

12 months

With reference to the applied inclusion criteria, all of the studies included have a prospective study design.

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157

Depression Anxiety

—

Grazing

Binge eating

—

—

C.L. Wimmelmann et al.

Alger-Mayer et al. [53]


Referencea

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Table 1 (Continued)


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Psychological predictors of surgical weight loss with women, men consume larger amounts of food at one time, leading to larger effects of restrictive surgical procedures. In contrast, women tend to eat more food high in sugar compared with men, which may lead to better results with malabsorptive or combined surgical procedures such as GBP. However, at least one study involving restrictive surgical procedure reported better weight outcome in women compared with men [31]. Future research should take pre-and postoperative eating behaviour into consideration when investigating the predictive role of demographic factors such as age and sex for surgical weight loss.

Cognitive function There is growing evidence that severe obesity is associated with impaired cognition independently of obesity-related medical comorbidities [67], especially with regard to memory and executive functions, such as planning, problem solving, and mental flexibility [68,69]. Cognitive dysfunction can be either a cause or a consequence of severe obesity [67]. Recent research has indicated that up to 23% of bariatric patients present for surgery with clinically important cognitive dysfunction (>1.5 SD below normative data) [70], which could contribute to difficulties in complying with the required postoperative lifestyle and to poor weight loss [67]. Gunstad et al. [70] found that bariatric patients at baseline generally performed within the low average to average range on the Integneuro cognitive test battery, which consists of estimated premorbid intellectual abilities and performance in several cognitive domains such as executive function, memory and attention, compared with normative data. Twelve weeks after surgery, the average performance of the surgical patients fell within average to above average range for all tests included in the battery, and the proportion of patients who performed >1.5 SD below normative data was reduced to 0—9.5% depending on the subtest. While preoperative cognitive dysfunction has been reported in a significant proportion of bariatric patients [70], preoperative cognitive function as a predictor of postoperative weight changes is not yet fully understood. We identified one eligible study that prospectively investigated the prognostic value of preoperative cognitive function for surgical weight loss. Among 84 bariatric patients undergoing GBP, Spitznagel et al. [43] found that some specific cognitive functions at baseline, especially verbal memory and attention/executive functions, predicted successful weight loss at 1-year followup after adjusting for demographic and medical

xxx.e7 factors. This result indicates that cognitive evaluation before surgery could be helpful in identifying patients who might benefit from a more intensive follow-up programme, such as increased number of postoperative supportive appointments and more extensive preoperative education. Since the reported cognitive deficits primarily have been of executive nature, it could be speculated that developing structured and detailed plans to patients with such deficits may be more helpful than the general guidelines currently provided. Future research should examine whether such postoperative supportive interventions facilitate better weight outcomes in bariatric patients with cognitive deficits.

Personality No single personality trait or personality type has consistently been related to obesity, but it is broadly recognised that personality factors affect health-related behaviours [71]. Past studies examining personality as a predictor of surgical outcome have almost exclusively used the Minnesota Multiphasic Personality Inventory (MMPI) to assess personality. In reviewing this research, Herpertz et al. [26] concluded that either personality traits do not predict postoperative weight loss, or the applied definitions of personality have been too broad. Currently, the five-factor model is the most widely used model of personality [72] and among the ‘‘big five’’ personality dimensions studies investigating associations between personality and health have primarily focused on neuroticism. High neuroticism is characterised by a relatively stable tendency to experience and express negative emotions in response to threat, frustration, and loss and has consistently been associated with increased body mass [73,74], inappropriate eating behaviour [75], and weight gain [76]. Furthermore, among obese individuals, impulsiveness, often considered a component of neuroticism, has been found to be the main predictor of emotionally and externally triggered eating behaviour [75]; two high-risk eating patterns often associated with severe overweight and weight gain [77—79]. Consistent with the observed association between neuroticism and high-risk eating behaviours in an obese population [75], among 44 GBP patients neuroticism was negatively associated with weight loss after surgery and this association was fully mediated by postoperative eating behaviour [44]. Similarly, Pontiroli et al. [46] reported that narcissism had a strong negative effect on both short-term weight loss and compliance with recommended rules after surgery,



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xxx.e8 but only adherence to scheduled visits and compliance with recommended rules predicted weight loss in the long-term. Based on these findings, there seem to be two possible ways personality can be related to weight changes after surgery. Either the relation between personality and postoperative weight changes is mediated by postoperative eating behaviour or specific personality traits independently predict postoperative weight outcome because they predispose to elevated stress levels [80,81] which in turn have been shown to have a negative effect on metabolism [82]. Using the Temperament Character Inventory (TCI) to assess personality, recent studies have provided more evidence of an association between personality and surgical weight loss [45,83]. Specifically, De Panfilis et al. [45] reported that pre-surgical scores on the ‘Persistence’ subscale explained more than 40% of the variance of BMI reduction at 1-year follow-up, even after controlling for demographic factors, psychopathology, and other temperament and character traits. Similarly, a short-term study that did not meet the inclusion criteria of the current review found that higher pre-surgical ‘Self Directedness’ on TCI was associated with greater weight loss 6 months after surgery [83]. Obesity surgery is a forced behaviour modification, and several non-surgical and behavioural factors are thought to affect outcome [24]. For instance, bariatric patients are required to adopt an appropriate health behaviour postoperatively and to attend regular clinical examinations up to two years after surgery. The TCI Persistence and Self Directedness scales both reflect temperamental tendencies compatible with the postoperative behavioural demands, suggesting that the observed associations between these temperament patterns and weight loss after surgery are mediated by adaptation of an appropriate health behaviour. The use of different assessment instruments based on different models of personality complicates interpretation of studies of personality as a predictor of post-surgical weight loss. Furthermore, all the reviewed studies assessed personality using self-report instruments. Although this is the standard method in most empirical personality research, some limitations of self-report may be particularly important in studies of personality and bariatric surgery. When self-report instruments are used, it is often difficult to distinguish between enduring personality traits and temporary emotional states which may influence scores on measures of personality traits and thus confound studies investigating personality as a predictor of surgical outcome. This highlights the methodological issue concerning the optimal time to assess

C.L. Wimmelmann et al. personality in bariatric patients since self-report inventories must be assumed to be affected by the emotional state of the patients before and after surgery. All studies assessed personality relatively short time before surgery, and the obtained personality scores may therefore reflect both stable personality traits and the emotional state of the participants including anxiety and worry about surgery and the outcome of the operation. Assessing personality postoperatively may also be problematic because positive emotions associated with immediate weight loss may influence self-report personality scores. In spite of the methodological problems, the available evidence corroborates hypothesis that personality may influence post-surgical weight loss, but the evidence also suggests that the influence of personality is primarily mediated through postsurgical eating behaviour.

Psychopathology It remains controversial whether psychopathology should be considered an impediment to obesity surgery. The correlation between psychopathology and morbid obesity is complex and poorly understood. Research has suggested that for some individuals, extreme overeating is a maladaptive reaction to negative emotions and psychological distress contributing to the development of obesity [84]. In contrast, social stigma and health consequences related to obesity may lead to mood or anxiety disorders in otherwise psychologically healthy individuals; yet, some morbidly obese individuals do not present psychopathology [85]. Thus, preoperative mental health status or psychopathology and postoperative weight loss can be related in several ways. If psychopathology is primary to obesity, preoperative levels of psychopathology may independently predict surgical weight loss. Alternatively, postoperative health behaviour may be influenced by preoperative psychiatric status leading to suboptimal weight loss. Psychological distress secondary to obesity is, on the other hand, highly likely to decrease with weight loss, which may contribute to better long-term weight loss maintenance. In this case, postoperative mental status might prove a better indicator of long-term weight loss compared to preoperative psychopathology. Several studies published in recent years have reported suboptimal weight loss in bariatric candidates with psychiatric disorders before surgery [48,50—52]. Among 140 patients Kinzl et al. [50] found that a combination of no psychiatric disorder, having an atypical eating disorder, and positive childhood experiences was associated with



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Psychological predictors of surgical weight loss the largest weight loss after surgery. In contrast, patients displaying a combination of two or more psychiatric disorders, adverse childhood experiences, but no eating disorder, were less likely to achieve a successful weight loss. In accordance, several studies [37,86] have demonstrated that having multiple psychiatric disorders negatively predict postoperative weight loss, suggesting that comprehensive assessment of preoperative mental health in bariatric candidates can improve the prediction of surgical outcome. Not surprisingly, the included studies indicated that psychopathology that persists postoperatively was associated with poor weight loss [37,50,52]. Additionally, in a postoperative study Scholtz et al. [87] reported that bariatric candidates diagnosed with a psychiatric disorder at the time of surgery did not differ from candidates without a psychiatric disorder in terms of surgical outcome. However, having a mental disorder after surgery was associated with a reduced likelihood to achieve a successful surgical outcome and a higher frequency of requiring a surgical reversal. Mental disorders are frequently associated with less flexibility and poor adaptability. Thus, bariatric patients with psychiatric disorders may have more difficulties adapting to the postoperative demands and therefore be at greater risk of poor surgical outcome. On the other hand, studies using self-report instruments have suggested that pre-surgical mental symptoms do not negatively predict surgical outcome [47,53]. A retrospective study that reviewed 145 patients charts [64] even found a positive correlation between baseline depression score, as measured on Becks Depression Inventory (BDI), and amount of excess weight loss at 1-year follow-up. In line with prior research [26], recent results are partly conflicting, indicating that the sole diagnosis of a psychiatric disorder is insufficient in predicting surgical weight loss. A possible explanation of the inconsistency involves the nature and severity of the psychiatric symptoms. In their review, Herpertz et al. [26] suggested that psychological distress related to obesity, such as mild depression, low self-esteem, and poor body image, has a positive effect on surgical weight loss. In contrast, bariatric patients with severe and chronic psychiatric disorders, such as personality disorders and major depression, may have more difficulties adjusting to the behavioural demands imposed by surgery and thus be less likely to achieve successful weight loss.

Binge eating disorder and eating behaviour A substantial part of the bariatric population presents for operation with BED or

xxx.e9 sub-clinical binge eating behaviour, such as overeating episodes, accompanied by a subjective loss of control and psychological distress. Recent reports of the prevalence of BED in the bariatric population range from 10% [55] to 50% [88], and sub-clinical binge eating behaviour has been reported to be as high as 80% [57]. Patients who binge eat do not differ from non-binge eating (NBE) patients in weight status before surgery [40], but are often characterised by greater psychosocial problems and significantly more psychiatric comorbidity [40,58]. Obesity surgery has a positive effect on several aspects of eating behaviour, including hunger, disinhibition, restrictive eating and binge eating, at least in short-term studies [26,54,55,89], but these improvements may decline when the initial surgical effect decreases [57,90]. It has been suggested that bariatric patients who binge eat have more difficulties adapting to the restrictive eating behaviour after surgery and therefore are at greater risk of poor weight loss [26,89]. Thus, preoperative binge status may indirectly predict weight loss mediated by postoperative eating behaviour. Alternatively, BED may be associated with reduced mental wellbeing and elevated stress levels, which have been shown to play an important role for metabolism [82]. BED at baseline could therefore be an independent predictor of weight outcome. Marked improvements in several aspects of eating behaviour after surgery, often measured by self-report instruments, such as the Three Factor Eating Questionnaire (TFEQ), have consistently been reported in both binge eating and non-binge eating bariatric patients [54,55]. In addition, several studies have demonstrated that pre-surgical BED does not predict weight loss after bariatric surgery [53—55,58]. For instance, Wadden et al. [54] found that bariatric surgery had the same positive effect on weight loss and medical risk factors in BED patients and NBE patients. At 12 months follow-up, patients with preoperative BED lost 22.1% of initial weight compared with 24.2% in NBE patients at 12 months follow-up. Furthermore, in both patient groups, weight loss was associated with clinically important reductions of cardiovascular risk factors. Some negative findings may reflect the use of inadequate follow-up periods [54,55,58], emphasising that the initial effect of surgery reduces the impact of pre-surgical eating factors. However, at least one long-term study found similar postoperative weight loss in binge eating and NBE patients persisting up to six years after GBP [53]. Furthermore, some of the reviewed studies have used self-report instruments to assess binge eating behaviour [53,58,59].



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xxx.e10 In contrast, Sallet et al. [57] assessed preoperative binge eating behaviour by DSM-IV clinical interviews and concluded that current or past binge eating behaviour was negatively associated with weight loss after GBP; the correlation occurred one year after surgery and was clearly manifested at 2-year follow-up. This conclusion is supported by a short-term study that did not meet the inclusion criterion of a minimum of one year follow-up period [88]. Yet interestingly, this study reported significant group differences as early as 6 months following GBP, with binge eating patients displaying higher scores on TFEQ-subscales of hunger and disinhibition and lower % EWL compared with NBE patients. Whereas the impact of pre-surgical binge eating on weight loss remains disputed, it has more consistently been demonstrated that postoperative eating behaviour is associated with surgical outcome [49,50,59]. Binge eating is physically impossible immediately after surgery; however, loss of control (LOC) over eating behaviour, which is an essential characteristic of BED, can remain postoperatively and lead to less successful weight outcomes. Using both diagnostic interviews and self-report questionnaires several studies have reported that pre-surgical factors do not predict long-term outcome after bariatric surgery, but the development or reemergence of binge eating symptoms postoperatively may be associated with suboptimal outcome [21,56,59]. For instance, White et al. [59] demonstrated that patients who reported LOC after GBP had poorer weight loss at both 1- and 2-year follow-up compared with patients who did not report LOC; with the impact of LOC becoming more apparent as the followup period increased. Postoperative complications, such as vomiting, plugging, and gastric dumping, which are likely to result from inappropriate eating behaviour after surgery, have been reported in up to ∼70% of patients after GBP [89,91,92] and may reflect the patients’ difficulty in learning to adjust to the postoperative diet. However, in 79 GBP patients Lanyon et al. [49] found that adaptation of a functional eating behaviour during the first year significantly predicted weight loss over the second and third year after surgery, indicating that eating behaviour in the first postoperative period is important for long-term weight outcome. Research has primarily studied the prognostic value of preoperative binge eating for postoperative weight loss. However, the essential question may concern the relationship between pre-and postoperative eating behaviour. There is some evidence that preoperative binge eating predicts inappropriate eating patterns after surgery. For instance, among 129

C.L. Wimmelmann et al. bariatric patients Colles et al. [56] found that over 60% of the patients with baseline BED reported grazing during the first postoperative year, 44% were categorised as ‘uncontrolled eaters’, and more than 33% met the criteria for both of the inappropriate eating patterns after surgery. This tendency has been supported by several previous studies [23,88,93—95], and it has been suggested that pre-surgical pathological eating, as a way of reducing psychological distress, is more likely to either persist or reoccur after surgery [89] and thus indirectly be negatively related to weight loss as opposed to inappropriate but non-pathological eating [96]. However, it must be emphasised that some of the included studies used self-report questionnaires to assess both psychopathology and eating behaviours. Higher levels of eating pathology have consistently been found using self-report questionnaires compared with interview-based assessment [97], and research has suggested that self-reported binge eating status among bariatric candidates is inaccurate [89,98]. Thus, it is likely that the use of self-report instruments in some of the reviewed studies has lead to false categorization of binge eating patients and thereby distorted potential differences between clinical patients and non-clinical individuals.

Multiple predictors The conflicting results may reflect the fact that the majority of studies have investigated the prognostic value of individual predictors. Lanyon and Maxwell [48] found that a combination of four composite factor-based variables representing physical/medical health, psychological health, interpersonal support, and eating disorder predicted weight loss one year after surgery. In contrast, none of the individual postoperative measures, except for high current life stress, demonstrated significant correlations with weight loss at 1-year follow-up. Interestingly, three different sets of variables representing expectations of increased self-esteem and social life, coping skills, and the presence of emotional and informational support, predicted weight loss 1—3 years postoperatively in the same sample [49]. The authors suggested that different predictors are relevant for short and long-term outcome; i.e. negative factors, which may interfere with weight loss, appear to predict initial outcome, and positive factors, such as superior mental and social resources, seem to predict weight change over the second and third postoperative year. One possible explanation is that the substantial effects of bariatric surgery on



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Psychological predictors of surgical weight loss both physical and emotional factors initially after surgery reduce the impact of some pre-surgical psychological variables, such as self-esteem and body image. However, the immediate surgical effects abate, and long-term weight loss may therefore depend on the patients’ ability to change and maintain appropriate health behaviours. This ability much be assumed to be associated with individual characteristics such as cognitive function, personality and mental health.

Long-term weight outcome Only one of the included studies conducted >5 year follow-ups. In a prospective study with 137 bariatric patients, Alger-Mayer et al. [53] assessed the predictive value of binge eating status, depression, and quality of life for postoperative weight loss up to 6 years after surgery. The authors found no significant differences between severe binge eaters and the rest of the group at any time point during the 6 years of follow-up in terms of total body weight loss, percent total body weight loss, or excess body weight loss. Similarly, patients with considerable depressive symptoms assessed by the BDI did not differ with respect to these weight loss outcomes over the 6 year follow-up period. Interestingly, the only significant findings were observed 5 and 6 years postoperatively where physical aspects of quality of life measured before surgery significantly impacted percent total body weight loss. However, at >5 year follow-up, the number of patients was small (n = 23), and the authors therefore speculated that these findings might reflect a statistical type 1 error since physical aspects of quality of life did not appear to influence weight outcome in the first five postoperative years. Alternatively, the substantial surgical effects may have reduced the impact of pre-surgical psychosocial factors in the first postoperative years explaining the delayed importance of physical aspects of quality of life. The American Society for Bariatric Surgeons [99] recommends that postoperative studies should conduct at least 5-year follow-ups, and that results obtained within the first two years should be considered preliminary. Furthermore, recent research has emphasised the importance of postoperative psychological factors in predicting long-term success of bariatric surgery. Unfortunately, the vast majority of prospective studies have mainly examined presurgical predictors and conducted follow-up after two years or less. Thus, more prospective long-term follow-up studies investigating both pre- and postoperative predictors of surgical success are highly needed.

xxx.e11

Conclusion Some tentative conclusions can be drawn from this review of recent prospective studies with at least 1-year follow-up examining predictors of postoperative weight loss. Herpertz et al. [26] concluded that personality and moderate psychiatric comorbidity did not predict surgical weight loss whereas severe psychiatric psychopathology may be a negative predictor of weight loss. The studies conducted in 2003—2012 have provided some evidence that individual characteristics such as cognitive function, personality, and composite psychological variables may influence postoperative weight loss. Our review of the more recent research indicates that cognitive impairments before surgery may predict poor weight outcome [43]. Only one study was identified that investigated the predictive value of cognition for bariatric weight loss, and further research on this subject is obviously needed since it is very likely that cognitive function influence the ability of patients to develop and maintain appropriate eating behaviours after surgery. Personality does not appear to independently predict surgical weight loss among bariatric patients [31,44,46]. However, research published in recent years has indicated that personality plays a role in the psychological and behavioural adjustment after surgery and thus has an indirect effect on weight loss. Prediction of postoperative weight loss has been the primary approach when assessing the relation between personality and surgical outcome. Although prediction of postoperative weight loss is an important approach to assessing the relation between personality and surgical outcome, it provides little knowledge of potential mediating factors, such as compliance and postoperative eating behaviour. Future research should focus on the effect of personality on postoperative health behaviour rather than merely study the prognostic value of personality for postoperative weight loss. With respect to the predictive value of presurgical mental status and the usefulness of screening for mental symptoms before surgery, some new findings have been reported. For instance, recent research has demonstrated that the total number of psychiatric diagnoses preoperatively [37,86] and the use of composite variables [48,49] are more efficient in identifying patients at risk of suboptimal weight loss. Furthermore, the effect of pre-surgical psychiatric disorders on the quality of the patients’ mental health and behaviour after surgery may be important for the postoperative weight course [56,59]. Finally, there is some evidence that predictors of short-term



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xxx.e12 weight loss differ from those predicting long-term weight loss [48,49,52,100], underscoring the importance of future prospective longitudinal research in the study of psychological predictors of surgical outcome. Binge eating status has been found to predict weight loss in some studies [57,88], whereas others [54,55,58] have reported that binge eating assessed before surgery does not predict weight loss. It may be speculated that the inconsistent results are related to differences in study design, including differences in assessment and diagnosis of binge eating. In line with prior research [26], recent studies have suggested that postoperative eating behaviour may be a more important determinant of surgical weight loss than preoperative eating factors. More specifically, uncontrolled eating and grazing have consistently been identified as high-risk eating behaviours after surgery, often associated with weight regain and mental distress [21,56,59]. Therefore, continuous monitoring and identification of high risk eating patterns after surgery and the development of supportive postoperative interventions are important to optimise surgical outcome for bariatric patients. Although the current review had fairly strict inclusion criteria, permitting only prospective studies with a sample size of at least 30 patients and a follow-up period of minimum one year, inconsistent findings have been reported for most investigated psychological predictors. Perhaps, the most consistent finding is that postsurgical eating behaviours influence postoperative weight loss and that the influence of pre-surgical psychological factors on postoperative weight loss seems to be mediated through associations with postoperative eating behaviours. This seems to be the case for pre-surgical cognitive function, personality, mental health, and binge eating disorders. In contrast, little consistent evidence indicates influence of these psychological factors on postoperative weight loss, which is independent of postoperative eating behaviours. These conclusions are tentative and future studies should focus on the interactions between pre-surgical psychological factors and postoperative eating behaviours and on identifying both psychological predictors and other postoperative behaviours including physical activity, which may influence postoperative weight loss.


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