How Eating Habits, Obesity, and Weight-Loss Surgery Are Related and Treated

Taking these factors into account, a search was performed on PubMed using the following keywords: "obesity", "eating behavior", "overweight and obesity—causes and risk factors", "eating desorders", "bariatric surgery", "eating behaviour and bariatric surgery", "weight loss", "eating issues", "obesity in adults/childrens", "indication/contraindications for MBS", "mass-media and eating behavior", and "type/criteria for binge eating disorder".

The search was limited to studies published in English in the last 10 years, OMS information about obesity (https://www.who.int/news-room/fact-sheets/detail/obesity-and-overweight↗ (accessed on 15 November 2024)), Obesity Atlas 2024 (https://data.worldobesity.org/publications/WOF-Obesity-Atlas-v7.pdf↗ (accessed on 15 November 2024)), and books about eating disorders.

The exclusion criteria were the patients with obesity and weight loss with diet or with medication treatment, intermittent fasting diet, and articles that did not address the topic studied in detail.

Figure 1 highlights the screening and selection process regarding the articles included in this review.

The screening process was conducted by three independent reviewers (I.M.A., B.M.C., M.M.) in duplicate. Full texts of the articles were carefully examined. Disagreements that appeared during the data abstraction phase were resolved through discussions between the reviewers. If an agreement could not be reached, a fourth reviewer (A.O.) made the final decision.

Evaluation of the patient's and family's ability and motivation to adhere to pre-operative and post-operative treatment plans, including consistent use of micronutrient supplements.

MBS does not adversely affect pubertal development or linear growth. Therefore, neither a specific Tanner stage nor bone age should be mandated as a prerequisite for surgery [13].

Candidates for MBS should undergo a comprehensive evaluation by a multidisciplinary team comprising medical, surgical, psychiatric, and nutritional specialists. This approach acknowledges the multifaceted nature of obesity and facilitates a thorough risk–benefit assessment. Additionally, such collaboration enhances the patient's understanding of the lifelong lifestyle modifications required post-surgery, leveraging the expertise of diverse healthcare providers.

Engagement with a multidisciplinary team enables the optimization of modifiable risk factors, aiming to minimize peri-operative complications and enhance surgical outcomes. The ultimate determination of surgical readiness, however, rests with the operating surgeon.

Globally, sleeve gastrectomy (SG) has emerged as the most frequently performed MBS procedure. Experts agree that SG is particularly suitable for high-risk patients, pediatric populations, and older adults (>65 years). However, SG may be less appropriate for individuals with obesity-related complications such as uncontrolled type 2 diabetes mellitus (T2DM), gastroesophageal reflux disease (GERD), or non-alcoholic steatohepatitis (NASH).

For patients with a BMI ≥ 50 kg/m², SG was the preferred procedure in 66.7% of cases, although no universal consensus was reached. Procedures such as biliopancreatic diversion with duodenal switch (BPD-DS) and sleeve gastrectomy with single-anastomosis duodenoileostomy (SADI) were considered suitable for patients with a BMI > 50 kg/m² and severe or uncontrolled diabetes. However, patients undergoing SADI require lifelong nutritional monitoring and supplementation to mitigate long-term risks associated with malabsorption [14].

The evaluation process for bariatric surgery includes a thorough review of the medical history, a detailed clinical interview, and psychological assessment. The psychological evaluation should be integrated into a multidisciplinary approach designed to systematically assess the risks and benefits of surgery for each patient. For patients with eating disorders, it is essential to emphasize that bariatric surgery alone will not resolve maladaptive eating behaviors. Sustainable weight loss requires ongoing efforts to modify lifestyle habits, including dietary practices and physical activity, as part of a comprehensive, long-term management plan [15].

Several factors are identified as risk determinants for the onset of obesity and eating disorders (EDs). A family history of obesity is considered a major risk factor for developing obesity, attributed to significant hereditary transmission patterns [15]. Consistent with this, data from the Collaborative Psychiatric Epidemiology Surveys (CEPES) [16] have demonstrated that individuals with obesity face an elevated lifetime risk of developing EDs compared to individuals with normal weight. Additionally, a family history of binge eating disorder (BED) has been recognized as a notable risk factor for the development of obesity in adulthood [17]. Furthermore, familial obesity is linked to both BED and bulimia nervosa (BN) [18], suggesting that genetic and environmental factors within families may predispose individuals to the development of these disorders, potentially influencing their susceptibility to both disordered eating behaviors and obesity later in life [15].

Genetic factors, particularly variations in genes associated with fat mass and obesity (e.g., FTO), expressed in the arcuate nucleus of the hypothalamus—a central area in appetite regulation—have consistently been associated with obesity [19]. Other candidate genes, such as melanocortin-4 receptor (MC4R) and brain-derived neurotrophic factor (BDNF), have also been implicated in increasing susceptibility to BED in adults [20]. These findings support the hypothesis that certain genetic variations linked to excessive food intake may overlap with those predisposing individuals to overweight and obesity [21]. Recent studies also indicate genetic correlations between anorexia nervosa (AN) and metabolic traits, which have led to the reconsideration of AN as a "metabo-psychiatric disorder" [22].

Psychological traits at the individual level have also been identified as risk factors for both EDs and obesity. Heightened reward dependence, impaired cognitive control, mood dysregulation, and difficulties in emotional regulation are significant factors contributing to binge eating episodes in individuals with obesity [23]. Furthermore, personality traits such as harm avoidance (i.e., the tendency to react strongly to adverse stimuli) and low self-directedness (i.e., the ability to adapt behaviors to achieve personal goals) have been noted as specific risk factors for EDs, particularly BED and BN, as well as for obesity [18,24]. Negative self-attitudes, such as low self-esteem, negative self-evaluation, and high body dissatisfaction, are also critical risk factors for BED [25].

Environmental factors also play a crucial role in the development of obesity and EDs. Childhood adversities, including emotional or physical abuse or sexual trauma, can significantly impact an individual's developmental trajectory, thereby increasing the risk for both obesity and EDs such as BED [24,26]. Other influential environmental factors include dietary patterns, media exposure, body image dissatisfaction, and weight-related bullying [17]. For instance, children with obesity are at an increased risk of being bullied in school, and individuals with a history of aggression have been found to have a heightened risk of developing EDs, particularly BED and BN [27].

Early identification of at-risk individuals, along with the implementation of preventive strategies, holds potential for reducing the burden of these conditions [28]. Identifying genetic markers for early detection of children predisposed to obesity could enhance strategies for managing eating behaviors in the future. Thus, current research efforts should prioritize the identification of biomarkers that indicate susceptibility to obesity and EDs, along with their shared risk factors, to facilitate early intervention and prevention [29].

Food addiction (FA) has garnered increasing attention as a factor associated with the development and maintenance of binge eating spectrum disorder (BSD) and obesity [30,31]. According to the FA model, the consumption of highly palatable foods—particularly ultra-processed foods rich in sugar, salt, and saturated fats—can lead to addictive behaviors, as these foods are particularly rewarding and can stimulate compulsive eating. The prevalence of FA has been reported to be 15.2% among adults in non-clinical populations and 15% in children and adolescents, with rates ranging from 15% to 25% in individuals with obesity [32]. Among individuals with EDs, FA is particularly prevalent, with rates of 60% in anorexia nervosa (AN), 81.5% in bulimia nervosa (BN), and 76.9% in BED [28,33]. FA is correlated with elevated ED symptomatology, general psychopathology, and poor treatment outcomes [16,34]. Additionally, FA is linked to negative urgency and low perseverance, personality traits commonly associated with emotional eating in individuals with obesity and EDs [35,36,37]. Despite the rarity of transitions from AN to BN or BED, higher FA rates in AN patients may indicate an increased risk of losing control over food intake [38]. Moreover, FA has been identified as a predictor of treatment outcomes in EDs, while it may also influence the extent of weight loss after bariatric surgery in patients with obesity [39].

The management of individuals with comorbid obesity and EDs requires a careful, nuanced approach to treatment planning [40]. While the primary goals for treating BN and BED include reducing or eliminating excessive food consumption and improving associated ED and general psychopathological symptoms, treatment objectives related to weight—particularly in BED—remain a topic of debate [41]. For obesity, the main therapeutic goals are weight loss and the maintenance of long-term weight reduction [42]. However, weight loss may often be the primary motivation for individuals seeking treatment for obesity, and some may be unaware of the presence of a comorbid ED [43]. Despite the lack of clear empirical evidence, there is concern that restrictive dietary interventions (e.g., as part of a lifestyle modification program) may exacerbate overeating behaviors or induce maladaptive eating patterns in individuals with comorbid conditions. As such, certain international treatment guidelines prioritize ED-specific treatment goals over weight management goals for patients with comorbid obesity and BED [40,44]. These guidelines recommend psychotherapy as the first-line treatment for BED, followed by interventions targeting weight loss [45]. However, there is a notable absence of cross-references between most international treatment guidelines for EDs and obesity, limiting clinical guidance for these individuals [44].

There is substantial evidence indicating that the marketing of unhealthy foods has a direct and detrimental impact on individuals across all age groups—children, adolescents, and adults—affecting their food preferences, choices, and consumption patterns. Numerous studies have identified food marketing as a significant determinant of dietary choices. Statistically significant associations have been observed between exposure to unhealthy food and beverage marketing via social media and increased consumption of such products, as well as weight gain [45].

Consequently, this form of marketing constitutes a recognized risk factor in the development of overweight and obesity. Research by Yuanqi Gu et al. further highlights a correlation between following unhealthy food and beverage brands on social media and elevated obesity rates in the United States [46]. The sharp increase in social media food advertisements over the past decade [47], coupled with the intensifying promotion of fast-food brands and sugary beverages on these platforms, is especially alarming [48]. Evidence suggests that exposure to such advertising is strongly linked to increased consumption of fast foods and high-calorie sugary drinks among youth [49].

Despite this significant public health issue, existing studies underscore the absence of comprehensive regulatory frameworks to curb the promotion of unhealthy foods on major social media platforms [50]. Gu et al.'s findings emphasize the urgent need for robust, integrated policies aimed at restricting the digital marketing of unhealthy food products [46].

Beyond current initiatives to encourage healthier food choices, innovative approaches are essential to promote positive dietary behaviors. Leveraging marketing strategies to endorse healthy foods could play a transformative role in improving dietary habits among both children and adults, fostering a preference for nutrient-dense foods and diverse food groups [51].

According to the Diagnostic and Statistical Manual of Mental Disorders, Fifth Edition (DSM-5) [92], binge eating disorder (BED) is characterized by the recurrent consumption of an unusually large quantity of food within a discrete period (approximately 2 h), accompanied by a perceived loss of control (LOC) over eating. This sense of LOC refers to an inability to regulate or halt food intake during binge episodes.

BED represents the most prevalent eating disorder among candidates for bariatric surgery. The Longitudinal Assessment of Bariatric Surgery (LABS) study reported that approximately 10% of bariatric surgery candidates fulfill the full diagnostic criteria for BED, a notable contrast to the general population prevalence of 1.2% [93]. It is worth noting that these rates may underestimate true prevalence, as bariatric candidates often underreport or downplay symptoms to avoid disqualification from surgery [93]. Additionally, many individuals with BED seek treatment for obesity rather than for disordered eating behaviors or the eating disorder itself.

To meet the DSM-5 diagnostic threshold for mild BED, individuals must engage in binge eating episodes at least once per week over the preceding 3 months, with such behaviors causing clinically significant distress. Among bariatric candidates, BED severity has been positively correlated with both the degree of obesity and the presence of psychopathology [94]. Specifically, the perceived LOC during binge episodes has been associated with heightened psychological distress [95] and more severe psychopathology, including elevated rates of depressive and anxiety disorders [96]. Furthermore, individuals with BED are more likely to exhibit additional maladaptive eating behaviors [94].

Currently, there is no standardized protocol for conducting pre-surgical psychological assessments, which may result in biased estimates of binge eating disorder (BED) prevalence and associated psychopathology [97]. The use of validated eating disorder assessment tools can help address this limitation by evaluating cognitive restraint over food intake, loss of control (LOC) eating, disinhibited eating, and hunger.

A growing area of research has focused on whether pre-surgical binge eating, or BED, predicts suboptimal weight loss outcomes following bariatric surgery. While numerous studies have been conducted, most have found no significant correlation between these factors, with only a minority suggesting an association between BED and less favorable weight loss outcomes. Consequently, the presence of binge eating, or BED, should not be regarded as a contraindication for bariatric surgery [98].

Nonetheless, it is crucial to closely monitor individuals with pre-surgical binge eating or BED in the post-operative period, as evidence indicates that disordered eating behaviors may re-emerge following surgery. This underscores the importance of comprehensive post-operative care and follow-up for this patient population [99,100,101].

Picking and nibbling (P&N) is characterized by unplanned, repetitive eating episodes occurring between main meals and snacks, with an indeterminate initial quantity of food to be consumed [102]. The term is frequently used interchangeably with 'grazing' [92]. P&N, or grazing behaviors, are prevalent among individuals with eating disorders, such as anorexia nervosa (AN), bulimia nervosa (BN), and binge eating disorder (BED) [102]. The classification of P&N as a disordered or maladaptive eating pattern remains ambiguous, particularly in the context of bariatric surgery candidates, who may adopt this behavior as a compensatory strategy to limit food intake in efforts to lose weight [102]. Evidence suggests that pre-operative grazing behaviors are associated with an increased likelihood of persisting post-operatively, thereby adversely affecting weight loss outcomes. Consequently, these patients may benefit from targeted interventions or structured nutritional programs aimed at optimizing food intake regulation [99].

Night Eating Syndrome (NES) is defined by a normal sleep–wake cycle accompanied by recurrent episodes of nocturnal eating, characterized by awakening from sleep to consume food (nocturnal ingestion) and excessive evening food intake, exceeding 25% of total daily caloric consumption. Evening hyperphagia occurs at least twice per week [103,104] and is indicative of a delayed circadian pattern of food intake [89].

For an NES diagnosis, individuals must demonstrate awareness of their eating behaviors—distinguishing NES from parasomnias, where recollection of eating episodes is minimal or absent. Additionally, the behavior must be associated with significant psychological distress and should not be more accurately classified as another eating disorder, such as binge eating disorder (BED).

In individuals with NES, the quantity of food consumed is typically less than what is observed during a binge eating episode [105]. Notably, approximately 15–20% of individuals with obesity meet the diagnostic criteria for both NES and BED [99,105]. Studies indicate that although the prevalence of NES is rising, about 17% of bariatric surgery candidates fulfill the criteria for this condition [98,105].

Pre-operative eating disorders, particularly binge eating, have been linked to a range of psychopathological conditions, including elevated rates of depression [94], mood disorders [96], reduced perceived interpersonal support, increased alcohol consumption [94], and diminished health-related quality of life (HRQoL). HRQoL refers to the influence of health status on an individual's functional capacity, encompassing both physical and mental health dimensions [106]. These domains are frequently and significantly compromised in bariatric surgery candidates [107,108], particularly among individuals with severe obesity and those with current or lifetime psychiatric disorders [109].

Although binge eating is physiologically unfeasible following bariatric surgery due to anatomical alterations, patients may continue to experience loss of control (LOC) eating and subjective episodes of overeating [111]. The highest-risk population comprises those who met the diagnostic criteria for binge eating disorder (BED) prior to surgery [100].

Conceição et al. estimated that approximately 10% of patients developed LOC episodes within two years post-surgery, with LOC reemerging as early as six months after the procedure. This behavior was associated with a range of complications [98,101], including vomiting, psychological comorbidities (e.g., depression), diminished health-related quality of life (HRQoL) [112], suboptimal short- and long-term weight loss, and increased weight regain [113,114].

As patients are unable to overeat post-operatively due to reduced gastric capacity, previous LOC eating behaviors may manifest as grazing or picking and nibbling (P&N) [110]. Consequently, inadequate weight loss and weight regain may stem not only from disinhibited eating but also from the gradual capacity to consume larger portions of food over time [115].

It is crucial to identify individuals at risk for LOC eating and monitor their eating behaviors and weight loss trajectory [116] utilizing instruments such as the Eating Disorder Examination—Bariatric Surgery Version 28, which provide more precise assessments of eating disorders following bariatric surgery.

Patients identified with LOC eating and concurrent psychopathological conditions may benefit from integrated interventions targeting both issues. However, these individuals may require additional support to maintain adherence to the post-operative diet, as evidence suggests that patients with BED or LOC eating behaviors are less likely to comply with dietary recommendations [115] and to attend follow-up appointments [117].

Grazing and snacking (P&N)/grazing represent common problematic eating behaviors following bariatric surgery [110], affecting approximately 30% of patients in this population [109]. A key challenge in distinguishing P&N from normal eating patterns [100] is that patients are instructed to consume multiple small meals throughout the day post-operatively. P&N, however, typically occurs spontaneously, without prior planning, often leading to the intake of calorie-dense foods or beverages [97]. Grazing has been linked to post-operative weight regain [109,110], although additional research is required to further elucidate the relationship between this behavior and long-term weight outcomes.

Currently, research on Nocturnal Eating Syndrome (NES) following bariatric surgery remains limited. However, it is generally observed to occur less frequently post-operatively [118]. A one-year follow-up study demonstrated a reduction in nocturnal eating behaviors, with prevalence decreasing from 17.1% pre-operatively to 7.8% post-operatively, though this study was confined to patients undergoing laparoscopic adjustable gastric banding (LAGB) [98]. Additionally, another study indicated an improvement in post-operative night eating symptoms in patients with pre-operative depressive mood disorders, compared to those without such mood disturbances. However, the relationship between depressive mood and NES is complex, with other factors, such as sleep disturbances, likely contributing to this predisposition [119].

It has been noted that insomnia and depressive symptoms typically improve in most patients within a short period following surgery. Currently, NES is primarily defined by the timing of eating episodes rather than their volume. Researchers hypothesize that although patients may continue engaging in nocturnal eating after surgery, the quantity consumed may be reduced [118]. Consequently, further prospective studies are needed to more comprehensively assess nocturnal eating behaviors in bariatric surgery patients [110].

Health-related quality of life (HRQoL) generally improves in the early post-operative period, encompassing both physical and mental health domains [93]. For instance, studies documenting long-term improvements in mental HRQoL have indicated that these improvements were primarily driven by weight loss but tended to diminish over time [120,121]. In patients exhibiting significant eating disorder symptoms post-surgery, binge eating disorder (BED) was associated with lower HRQoL and with frequent grazing behaviors occurring two or more times per week [110]. A similar trend was observed in another long-term follow-up study, where the presence of binge eating negatively impacted mental HRQoL nearly 14 years after surgery [122].

Thus, while initial positive changes in HRQoL and eating behaviors are commonly observed following bariatric surgery, there appears to be considerable variability in outcomes over time. In some studies, these outcomes were influenced by the type of surgery performed and were related to the extent of post-surgical weight loss [123]. This underscores the importance of long-term monitoring of eating behaviors and dietary patterns in this patient population.

Some studies suggest that traditional eating disorders (ED), such as anorexia nervosa (AN) and bulimia nervosa (BN), may emerge in a subset of patients following bariatric surgery [,]. ^{117 124}