As a rule, in severe obesity, the efficacy of non-operative therapy disappointing, while in the most cases, bariatric surgery is followed by a highly satisfactory and well-maintained weight outcome [1, 2]. The Roux-en-Y gastric bypass (RYGPB) and the sleeve gastrectomy (SG) are the most commonly used bariatric procedures: the primary aim of these operations is the forced limitation of the alimentary intake by physically restricting the gastric passage of food. Furthermore, the new anatomo-functional gastrointestinal conditions resulting from the operation produce specific changes in the entero-hormonal pattern. Following RYGBP the production and secretion of GIP and GLP-1 increases, with development of early satiation with minimal amount of food, and following SG the production and secretion of the appetite stimulant ghrelin is minimized or abolished [3,4,5]: these physiological events lead to an additional reduction of food intake that is substantially independent of individual willing. In addition, after the operation, most of patients show a normalization of the eating behavior that usually is deranged in most obese patients [6, 7]. In the operated patients, these mechanical, physiological, and behavioral events cause a reduction of food consumption and, therefore, a significant weight loss. When the energy intake reduced for the limited alimentary consumption matches the body energy expenditure decreased for the weight loss, body weight stabilizes at lower levels than at the baseline and remains substantially unchanged unless the food intake start increasing once again [8]. The steadily weight loss corresponds to the disappearance/improvement of the obesity-related metabolic complications: furthermore, in comparison with control severe obese patients, in the operated subjects, a reduction of incidence of cardiovascular events and a lower overall mortality was observed [9, 10]. However, obesity surgery does not lead to recovery from severe obesity in all cases: in some patients, the postoperative weight reduction is fully unsatisfactory, or at long term, the obese status recurs, with complete loss of the metabolic benefits of the operation [11, 12]. The clinical practice suggests that abnormal eating patterns are frequently associated with excessive alimentary intake: therefore, it can be hypothesized that the persistence or the development of a disordered eating behavior following bariatric surgery could influence the weight results. In this view, this paper focuses the association of the weight outcome following bariatric surgery and the patient’s eating pattern both prior to and after the operation.

Patients and methods

The study was carried out in a cohort of 88 (15 man) consecutive obese patients undergoing Roux-en-Y gastric bypass (RYGBP, 56 cases) and Sleeve Gastrectomy (SG, 32 cases) according to the standard indications [13]. Patients with overt type 2 diabetes were not considered, all patients signed the informed consent for the operation and for the anonymous data processing. Before the operation, besides the usual anthropometric and clinical evaluations, all patients underwent an accurate alimentary interview by a registered dietitian specifically trained for detecting abnormal eating behaviors: the individual behavior was carefully checked for binge eating according to the American Psychiatric Association criteria [14] and for nibbling/grazing, identified as continuous consumption of small amount of food over an extended period of time [15]. The patient was regarded as eating disordered (ED) when referred one or both of these eating behaviors frequently recurring in the last 6 months. In all cases, a preoperative psychiatric evaluation did not reveal any specific contraindication to bariatric surgery.

After the operation, the patients attended a surgical/dietician follow-up at the third and sixth postoperative months and at the first and second postoperative years. At the follow-up visits, the patients received instructions for adopting an eating pattern as much adequate to the new anatomical and functional conditions created in the upper gastro-enteric tract by the operation: they were encouraged to eat with regularity, to have small meals, to avoid energetic beverages and too dressed foods, to refrain snacking between meals, and to keep of food when not physically hungry. In addition, throughout all the follow-up period, specific behavioral/dietitian sessions on these issues were delivered by a specifically skilled dietitian upon individual request. Throughout all the follow-up period, 22 patients received 1–5 additional behavior/dietetic sessions. At the first and second postoperative years, the weight loss was quantified as percent of body mass index loss (% Δ BMI) and the alimentary interview was repeated with the same aims and the same methodology than at the baseline. Differences between means were assessed by t test for longitudinal and cross-sectional findings, and category data were analyzed by the Chi-square and McNemar tests when appropriate. The rho Spearman test was employed to assess the relationship between the numbers of the dietetic-behavioral sessions delivered throughout the entire follow-up period and the  % Δ BMI at the second postoperative year. Calculations were carried out with STATA 14.2, College Station, TX, USA.

Results

In both RYGBP and SG patients, a marked weight loss was observed at the first postoperative year and the body weight (BW) and body mass index (BMI) values have remained substantially unchanged at the second one (Table 1). The follow-up rate was 83% at 1 year and 77% at 2 years after the operation, without differences between RYGBP and SG group. In the RYGBP patients, the BW and BMI values were significantly lower than in their SG counterparts both at 1 and 2 years following the operation: furthermore, the percent of BMI loss was greater in the former than in the latter group (Table 1). Prior to the operation, the patients having complained an eating disturbance (ED) showed BW and BMI values very similar (124 kg ± 18 vs. 118 kg ± 22 and 46 kg/m2 ± 5.4 vs. 47.3 kg/m2 ± 1 0.7, respectively) to those of individuals having reported a completely normal eating pattern. On the contrary, in the non-ED patients, the  % Δ BMI was greater than in the ED ones both at the first (30.7% ± 8.5 vs. 26.8% ± 10, p < 0.02) and second postoperative years (32% ± 10.3 vs. 27.4% ± 12.9, p < 0.05 (Fig. 1). As it is referred to in Table 1 and Fig. 2, nearly, three quarters of the preoperative obese patients referred ED before the operation, without difference between RYGBP and SG patients. Following the RYGBP, the number of ED patients reduced at 1 year and remained unchanged at longer term, while in the SG group, the number of patients having reported ED did not show any variation throughout all the follow-up period. The number of additional behavioral/dietetic sessions delivered throughout the entire follow-up period in the SG patients was positively related to the % Δ BMI (ρ = 0.42, p < 0.03 at 1 year and 0.039, p < 0.04 at 2 years, respectively), while the variables were fully unrelated in the patients having undergone RYGBP.

Table 1 Anthropometric and eating disturbance data of patients having undergone bariatric surgery
Full size table
Fig. 1
figure 1

Percent of BMI loss (% Δ BMI) at 1 and 2 years after bariatric surgery in patients referring (ED) and not referring (not ED) eating disturbance

Full size image
Fig. 2
figure 2

Patients having undergone Roux-en-Y gastric bypass (RYGBP) and sleeve gastrectomy (SG). Subjects reporting eating disturbance (ED) prior to the operation and at the first and the second follow-up period

Full size image

Discussion

Binge eating in an aberrant alimentary behavior commonly reported by most obese individuals, and more than half of patients seeking bariatric surgery complain about this eating disturbance [6, 16, 17]. Classically, binge eating is characterized by an ingestion of large amount of aliments in short time accompanied by a sense of loss of control over eating, including the feeling of being unable to stop eating or control the amount of food eating [14]. RYGBP and SG imply a gastric restriction that dramatically changes the amount of aliments that can be eaten: therefore, in most patients after the operation, a true binge episode became physically impossible [6, 18, 19]. On the contrary, the loss of control over food intake, a substantial component of the binge eating feature, is not affected by the anatomical modifications of the upper gastrointestinal tract. Therefore, after bariatric surgery, binge eating may turn in nibbling/grazing, preserving, however, the same alimentary or psychological meaning. Therefore, supported by theoretical hypothesis, in this study, the binge behavior and the nibbling/grazing were considered as two faces of the same coin, and patients were considered as eating disordered when reported frequent binge eating or nibbling/grazing both prior and following the operation [18,19,20,21].

In the current work-up of the bariatric patients, the adherence to postoperative dietetic prescriptions and guidelines is a significant challenge for many patients: the loss to follow-up actually influence the clinical significance of any investigations dealing with the role of the post-bariatric surgery behavioral/dietetic support [22,23,24]. In this study, besides the standard follow-up visits, specific behavioral/dietetic session were delivered only on a voluntary basis: therefore, it is possible to distinguish a priori a compliant vs. a not compliant subject and concentrate the heath care professional on the well-disposed subjects.

The first finding of this study is that, while before the operation the presence of a disordered eating does not influence the degree of obesity, at 1 and 2 years after RYGBP and SG, the subjects complaining binge eating or nibbling/grazing (eating disordered patients) experience a lower weight loss than the individuals reporting a normal eating pattern. This fully confirms previous data [18, 20, 25], and therefore, it can be suggested that, besides gastric restriction and changes in the entero-hormonal pattern, the improvement of eating behavior plays a substantial role in the weight loss mechanisms after bariatric surgery.

In addition, this investigation indicates that after RYGBP, a substantial improvement of eating behavior takes place at the first postoperative years, and it is well maintained at the second year, while following SG the eating behavior remains substantially unchanged and at 2 years after the operation nearly half of patients still refers eating disturbances. This could explain the better weight loss results after RYGBP than after SG observed in this study and reported in previous investigations [26, 27]. After RYGBP, the gastric restriction gives a heavy and painful sense of epigastric fullness after eating that induces braking food intake and acts as negative reinforcement for overeating; furthermore, the increasing in GIP and GLP-1 secretion stimulates satiety and strongly refrain to gorging. Moreover, the upper gastrointestinal adjustments caused by the operation physically prevent the resumption of the earlier eating habits and then disable the resistances to change. For these reasons, the operated subjects are compelled to shape new eating habits that are substantially adequate to the novel anatomy of the upper enteric tract: the operated subjects learn stopping overeating and avoiding inappropriate eating behaviors and overall permanently reduce the everyday food intake. It can by hypothesized that RYGBP works as a true learning machine, that can induce an appropriate eating behavior independently of any therapeutic boost. Finally, the satisfactory weight loss obtained in the first postoperative phases is a very strong positive reinforcement to make persistent the new eating style, thus warranting the weight loss maintenance at long term. It may be suggested that following SG this chain of events does not occur, the eating behavior fails to change and the weight loss is less evident. As additional finding, as it was observed by the previous study in gastric banding patients [28], after SG a positive association between the amount of weight loss expressed as % Δ BMI and the number of additional number of postoperative behavioral-dietetic session was found, while these variables were fully unrelated in the RYGBP subjects. Therefore, it can be suggested that the early satiety due to the post-RYGBP increase of GIP and GLP-1 release plays a main role in shaping a novel eating pattern that in most cases proved to be fully adequate for a reduced body weight; by consequence, the postoperative behavioral/dietetic support appears to be useless. On the contrary, the behavioral/dietetic sessions delivered on a voluntary basis might be of noticeable help for inducing weight loss after SG and gastric banding, bariatric procedures that seem not giving substantial results in shaping a novel eating pattern by themselves.

As limitation of this investigation, the retrospective design might introduce selection bias and confounding factors that could have undue influence on the analysis of the data. Because of the higher degree of obesity in the SG patients than in the RYGBP ones, the BW and BMI absolute values were not taken into account and the weight loss was considered as normalized for the baseline BMI value. Furthermore, the cohort of this study includes only consecutive patients receiving a standardized follow-up, in that minimizing the sources of error. On the opposite hand, the strength of this investigation is the follow-up, that is at longer term and rather more accurate than that reported in the majority of the studies dealing with eating behavior following bariatric surgery.

In conclusion, this investigation indicates that at 1 and 2 years after bariatric surgery the normalization of eating behavior has a substantial role in the postoperative weight loss. The postoperative improvement of the eating pattern takes place mainly after RYGBP, while the percent ED patients remain unchanged after SG, and this could explain the different weight outcomes between the two types of operations. It can be suggested that a behavioral/dietetic support is indicated in all patient having undergone SG, while after RYGBP, it might be useful only in patients who have shown an unsatisfactory weight loss.