Roux-En-Y Gastric Bypass and Sleeve Gastrectomy Does Not Affect Food Preferences When Assessed by an Ad libitum Buffet Meal

Weight loss in adult male Wistar rats by Roux-en-Y gastric bypass is primarily explained by caloric intake reduction and presurgery body weight

Diets varying in macronutrient composition, energy density, and/or palatability may cause differences in outcome of bariatric surgery. In the present study, rats feeding a healthy low-fat (LF) diet or an obesogenic high-fat/sucrose diet (HF/S) were either subjected to Roux-en-Y gastric bypass surgery (RYGB) or sham surgery, and weight loss trajectories and various energy balance parameters were assessed. Before RYGB, rats eating an HF/S (n = 14) diet increased body weight relative to rats eating an LF diet (n = 20; P < 0.01). After RYGB, absolute weight loss was larger in HF/S (n = 6) relative to LF feeding (n = 6) rats, and this was associated with reduced cumulative energy intake (EI; P < 0.05) and increased locomotor activity (LA; P < 0.05-0.001), finally leading to similar levels of reduced body fat content in HF/S and LF rats 3 wk after surgery. Regression analysis revealed that variation in RYGB-induced body weight loss was best explained by models including 1) postoperative cumulative EI and preoperative body weight (R2 = 0.87) and 2) postoperative cumulative EI and diet (R2 = 0.79), each without significant contribution of LA. Particularly rats on the LF diet became transiently more hypothermic and circadianally arrhythmic following RYGB (i.e., indicators of surgery-associated malaise) than HF/S feeding rats. Our data suggest that relative to feeding an LF diet, continued feeding an HF/S diet does not negatively impact recovery from RYGB surgery, yet it promotes RYGB-induced weight loss. The RYGB-induced weight loss is primarily explained by reduced cumulative EI and higher preoperative body weight, leading to comparably low levels of body fat content in HF/S and LF feeding rats.NEW & NOTEWORTHY Relative to feeding an LF diet, continued feeding an HF/S diet does not negatively impact recovery from RYGB surgery in rats. Relative to feeding an LF diet, continued feeding an HF/S diet promotes RYGB-induced weight loss. The RYGB-induced weight loss is primarily explained by reduced cumulative EI and higher preoperative body weight, leading to comparably low levels of body fat content in HF/S and LF feeding rats.

Changes in Food Preferences Before and After Intragastric Balloon Placement

BACKGROUNDS

In recent years, numerous studies have tried to decode the way bariatric surgery works toward weight reduction by the use of food preference questionnaires. The intragastric balloon has gained popularity, mainly due to its limited invasiveness, in patients with obesity not fulfilling criteria for bariatric surgery. However, there is no study assessing the changes in food preferences [FP]. We decided to analyze the FP of individuals prior to intragastric balloon insertion and following its removal, on the strict condition that participants must complete the 6-month treatment period and attend at least 4 of the 7 follow-up interviews.

METHODS

Patients were asked to rate the frequency of consumption of 63 food items before balloon insertion, at monthly intervals and after balloon removal. The food categories were protein, carbohydrates, fruit and vegetables, and sweets and fats.

RESULTS

The questionnaires of 320 participants were analyzed. A reduced frequency in consumption of meat and meat products, high-fat, and high-carbohydrate/sugary products and an increase in raw vegetables and fruit was found in all individuals.

CONCLUSION

The intragastric balloon seems to exert analogically similar mechanisms to bariatric surgery for weight loss, both functioning through alterations in FP. These are dictated by the anatomical re-configuration of the stomach, but mainly by counseling of dieticians and the self-education of the patient after experiencing unpleasant postprandial discomfort.

Control of Eating Attributes and Weight Loss Outcomes over One Year After Sleeve Gastrectomy

PURPOSE

Sleeve gastrectomy (SG) is a commonly performed metabolic-bariatric surgery, but its effectiveness is variable and difficult to predict. Our study aimed to compare control of eating (CoE) attributes pre- and post-SG depending on the achievement of optimal weight loss target at 1 year post-SG.

MATERIALS AND METHODS

A prospective longitudinal cohort study using the CoE Questionnaire, pre-SG, and postoperatively at 3, 6, and 12 months was conducted. Total weight loss (TWL) ≥ 25% at 12 months post-SG was set as an optimal weight loss target.

RESULTS

Forty-one patients (80.5% females, mean age 41.7 ± 10.6) were included. Sex, age, baseline weight, BMI, and smoking status were all comparable. At 3 months post-SG, "difficulty to control eating" score became significantly different between ≥ 25%TWL and < 25%TWL groups (7 [0-50] vs. 17 [5-63], p = 0.042). At 6 months, it was followed by "feeling of fullness," "frequency of food cravings," and "difficulty to resist cravings" demonstrating significant differences between ≥ 25%TWL and < 25%TWL groups. At 12 months, significant differences between groups were observed in "feeling hungry," "difficulty to resist cravings," "eating in response to cravings," and difficulty to control eating scores.

CONCLUSION

Individuals with obesity who achieved a target of ≥ 25%TWL at 1 year post-SG have an early improvement in overall eating control at 3 months that steadily persists at 6 and 12 months. Improvements in other aspects tend to follow later, at 6 and 12 months. These findings may assist in identifying individuals with inadequate response to help attain optimal weight loss targets and developing a prognostic model to identify predictors of successful weight loss.

Changes in food preferences and ingestive behaviors after glucagon-like peptide-1 analog treatment: techniques and opportunities

BACKGROUND

Glucagon-like peptide-1 (GLP-1) analogs are approved for the treatment of obesity in adults and adolescents. Reports have emerged that the weight loss effect of these medications may be related to changes in food preferences and ingestive behaviors following the treatment. Understanding the mechanisms which impact ingestive behavior could expand opportunities to develop more refined and personalized treatment options for obesity.

METHODS

Recent studies investigating the relationship between GLP-1 analogs and ingestive behaviors were retrieved from PubMed using the search terms: "obesity," "food preference," "taste," "ingestive behavior," "weight loss medication," "anti-obesity medication," "GLP-1 analog," "tirzepatide," "liraglutide," "semaglutide." Measurement tools were studied to compare variables used to assess food intake behavior. The main outcomes from each study were analyzed to evaluate the current standing and future directions of appetitive, ingestive, and consummatory behaviors and their association with GLP-1 analogs.

RESULTS

Thus far, studies have primarily explored the weight loss phase and report decreased short-term appetite and food intake upon treatment. However, research during the weight maintenance phase and objective measurements of food intake are notably sparse. Additionally, verbal reports have been primarily used to examine food intake, which can be susceptible to subjectivity.

CONCLUSIONS

Elucidating the relationship between GLP-1 analogs and ingestive behavior could reveal additional parameters which contribute to their anti-obesity effects. To better understand these mechanisms, it is imperative to consider objective measurements of food intake in future studies. Several measurement tools have been adapted to measure variables of food behavior in humans, and each must be carefully considered with their strengths and limitations to develop optimal investigations.

Obesity surgery and neural correlates of human eating behaviour: A systematic review of functional MRI studies

Changes in eating behaviour including reductions in appetite and food intake, and healthier food cue reactivity, reward, hedonics and potentially also preference, contribute to weight loss and its health benefits after obesity surgery. Functional magnetic resonance imaging (fMRI) has been increasingly used to interrogate the neural correlates of eating behaviour in obesity, including brain reward-cognitive systems, changes after obesity surgery, and links with alterations in the gut-hormone-brain axis. Neural responses to food cues can be measured by changes in blood oxygen level dependent (BOLD) signal in brain regions involved in reward processing, including caudate, putamen, nucleus accumbens, insula, amygdala, orbitofrontal cortex, and top-down inhibitory control, including dorsolateral prefrontal cortex (dlPFC). This systematic review aimed to examine: (i) results of human fMRI studies involving obesity surgery, (ii) important methodological differences in study design across studies, and (iii) correlations and associations of fMRI findings with clinical outcomes, other eating behaviour measures and mechanistic measures. Of 741 articles identified, 23 were eligible for inclusion: 16 (69.6%) longitudinal, two (8.7%) predictive, and five (21.7%) cross-sectional studies. Seventeen studies (77.3%) included patients having Roux-en-Y gastric bypass (RYGB) surgery, six (26.1%) vertical sleeve gastrectomy (VSG), and five (21.7%) laparoscopic adjustable gastric banding (LAGB). The majority of studies (86.0%) were identified as having a very low risk of bias, though only six (27.3%) were controlled interventional studies, with none including randomisation to surgical and control interventions. The remaining studies (14.0%) had a low risk of bias driven by their control groups not having an active treatment. After RYGB surgery, food cue reactivity often decreased or was unchanged in brain reward systems, and there were inconsistent findings as to whether reductions in food cue reactivity was greater for high-energy than low-energy foods. There was minimal evidence from studies of VSG and LAGB surgeries for changes in food cue reactivity in brain reward systems, though effects of VSG surgery on food cue reactivity in the dlPFC were more consistently found. There was consistent evidence for post-operative increases in satiety gut hormones glucagon-like-peptide 1 (GLP-1) and peptide YY (PYY) mediating reduced food cue reactivity after RYGB surgery, including two interventional studies. Methodological heterogeneity across studies, including nutritional state, nature of food cues, post-operative timing, lack of control groups for order effects and weight loss or dietary/psychological advice, and often small sample sizes, limited the conclusions that could be drawn, especially for correlational analyses with clinical outcomes, other eating behaviour measures and potential mediators. This systematic review provides a detailed data resource for those performing or analysing fMRI studies of obesity surgery and makes suggestions to help improve reporting and design of such studies, as well as future directions.

Mechanisms of Action of Bariatric Surgery on Body Weight Regulation

Bariatric surgery is an effective treatment modality for obesity and obesity-associated complications. Weight loss after bariatric surgery was initially attributed to anatomic restriction or reduced energy absorption, but now it is understood that surgery treats obesity by influencing the subcortical areas of the brain to lower adipose tissue mass. There are three major phases of this process: initially the weight loss phase, followed by a phase where weight loss is maintained, and in a subset of patients a phase where weight is regained. These phases are characterized by altered appetitive behavior together with changes in energy expenditure. The mechanisms associated with the rearrangement of the gastrointestinal tract include central appetite control, release of gut peptides, change in microbiota and bile acids. However, the exact combination and timing of signals remain largely unknown.

Mechanisms of bariatric surgery for weight loss and diabetes remission

Obesity and type 2 diabetes(T2D) lead to defects in intestinal hormones secretion, abnormalities in the composition of bile acids (BAs), increased systemic and adipose tissue inflammation, defects of branched-chain amino acids (BCAAs) catabolism, and dysbiosis of gut microbiota. Bariatric surgery (BS) has been shown to be highly effective in the treatment of obesity and T2D, which allows us to view BS not simply as weight-loss surgery but as a means of alleviating obesity and its comorbidities, especially T2D. In recent years, accumulating studies have focused on the mechanisms of BS to find out which metabolic parameters are affected by BS through which pathways, such as which hormones and inflammatory processes are altered. The literatures are saturated with the role of intestinal hormones and the gut-brain axis formed by their interaction with neural networks in the remission of obesity and T2D following BS. In addition, BAs, gut microbiota and other factors are also involved in these benefits after BS. The interaction of these factors makes the mechanisms of metabolic improvement induced by BS more complicated. To date, we do not fully understand the exact mechanisms of the metabolic alterations induced by BS and its impact on the disease process of T2D itself. This review summarizes the changes of intestinal hormones, BAs, BCAAs, gut microbiota, signaling proteins, growth differentiation factor 15, exosomes, adipose tissue, brain function, and food preferences after BS, so as to fully understand the actual working mechanisms of BS and provide nonsurgical therapeutic strategies for obesity and T2D.

Post-bariatric changes in ingestive behavior: Shift in macronutrient preferences in rats and dynamic adaptation of the within-meal microstructure in humans

This invited review is based on a presentation given at the Annual Meeting of the Society for the Study of Ingestive Behavior in July 2022 and provides the summary of two recent studies on changes in ingestive behavior following bariatric surgery (BS). First, long-term changes in daily absolute and relative macronutrient intake are reported in a rodent model of Roux-en-Y gastric bypass (RYGB). Rats undergoing RYGB progressively decreased their daily calorie- and daily fat intake compared to their preoperative baseline and to the intake of sham operated animals. Second, postbariatric changes in the within-meal ingestive microstructure are portrayed, based on longitudinal data collected in RYGB patients using a drinkometer. The post-RYGB meal size showed a dynamic adjustment process, with the highest decrease in the early postoperative phase, followed by a steady convalescence up to 1-year, at which point the meal size of RYGB patients became comparable to the normal weight adults'. Results are contextualized and contrasted to recent reports on the effect of BS on taste and food choices and consumption. The showcased evidence supports the role of ingestive adaptation and learning in the achievement of reduced calorie intake after RYGB, both in humans and in rodents. The reorganized upper-gastrointestinal anatomy supposedly leads to increased postingestive caloric sensibility, which might be an important behavioral mediator of decreased postbariatric meal size and consequent weight loss.

Is Food Tolerance Different After Bariatric Surgery Depending on the Surgical Procedure?

BACKGROUND

Bariatric surgery (BS) is a very effective treatment regarding body weight loss but might affect food tolerance and energy and protein intake. The aim of this study was to compare three BS techniques (biliopancreactic diversion (BPD), gastric bypass (GB), and sleeve gastrectomy (SG)) and their effect on food tolerance.

METHODS

Prospective study conducted between April 2016 and April 2019. Visits included were 1 before and 6, 12, and 24 months after BS. Food tolerance test (FTT), 24-h recall, and bioelectrical impedance (TANITA MC780) were performed at all visits.

RESULTS

Sixty-six patients were included (74.2% women). FTT showed a better self-perception of the intake after surgery in BPD at 6 months (p = 0.013), and at 12 months (p = 0.006). BPD had a better tolerance of 8 food groups at 6 months (red meat p = 0.017, white meat p = 0.026, salad p = 0.017, bread p < 0.001, rice p = 0.047, pasta p = 0.014, fish p = 0.027) and at 12 months, but only red meat (p = 0.002), bread (p < 0.001), rice (p = 0.025), and pasta (p = 0.025) remained statistically different. Twenty-four months after surgery, only the red meat food group (p = 0.007) showed differences. BPD had the lowest incidence of vomiting at 6 months (p < 0.001), 12 months (p = 0.008), and 24 months (p = 0.002). The total score of FTT was better in BPD at 6 months [25.6 (SD 1.5), p < 0.001], 12 months [25.6 (SD 2.4), p < 0.001], and 24 months [25.7 (SD 1.3), p = 0.001]. BPD showed the best intake in energy and proteins at 6 months [1214.8 (SD 342.4) kcal and 67.1 (SD 18.4) g] and 12 months [1199.6 (SD 289.7) kcal and 73.5 (SD 24.3) g]. % FML was higher in GB both at 6 and 12 months being statistically different (p < 0.050).

CONCLUSION

Biliopancreatic diversion appears to be the technique with a better food tolerance and protein and energy intake in the first year of follow-up after BS.

Food preferences after bariatric surgery: a review update

Obesity is a serious and global health problem. The multiple complications of obesity reduce quality of life and increase mortality. Bariatric surgery is one of the best treatment options for obesity management. Bariatric surgery helps people reduce their caloric intake by treating the disease of obesity effectively, in part by increasing signaling from the gut to the brain. The most frequent surgical options are Roux-en-Y gastric bypass (RYGB) and sleeve gastrectomy (SG). There is controversy regarding changes in food preferences and selection after bariatric surgery. In this review, we aim to outline the changes in food intake and selection, clarify the behavior changes in food intake, and assess the potential mechanisms responsible for these changes in patients after bariatric surgery.

A specific tongue microbiota signature is found in patients displaying an improvement of orosensory lipid perception after a sleeve gastrectomy

Introduction

A preferential consumption of low-fat foods is reported by most of the patients after a vertical sleeve gastrectomy (VSG). The fact that a recent study shed light on a relationship between oral microbiota and fat taste sensitivity in obese patients prompted us to explore whether such a connection also exists in the context of a VSG.

Methods

Thirty-two adult female patients with a severe obesity (BMI = 43.1 ± 0.7 kg/m²) and candidates for a VSG were selected. Oral microbiota composition surrounding the gustatory circumvallate papillae (CVP) and the lipid perception thresholds were explored before and 6 months after surgery.

Results

VSG was found to be associated both with a qualitative (compositional changes) and quantitative (lower gene richness) remodeling of the peri-CVP microbiota. Analysis of the lipid perception allowed us to distinguish two subgroups: patients with a post-operative improvement of the fat taste sensitivity (i.e., with a lower threshold, n = 14) and unimproved patients (n = 18). Specific peri-CVP microbiota signatures also discriminated these two subgroups, unimproved patient being characterized by higher levels of Porphyromonas, Fusobacterium, and Haemophilus genera associated with lower levels of Atopobium and Prevotella genera as compared to the lipid-improved patients.

Conclusion

Collectively, these data raise the possibility that the microbial environment surrounding gustatory papillae might play a role in the positive changes of fat taste sensitivity observed in some patients after VSG.

Macronutrient intake: Hormonal controls, pathological states, and methodological considerations

A plethora of studies to date has examined the roles of feeding-related peptides in the control of food intake. However, the influence of these peptides on the intake of particular macronutrient constituents of food - carbohydrate, fat, and protein - has not been as extensively addressed in the literature. Here, the roles of several feeding-related peptides in controlling macronutrient intake are reviewed. Next, the relationship between macronutrient intake and diseases including diabetes mellitus, obesity, and eating disorders are examined. Finally, some key considerations in macronutrient intake research are discussed. We hope that this review will shed light onto this underappreciated topic in ingestive behavior research and will help to guide further scientific investigation in this area.

Food Intake Following Gastric Bypass Surgery: Patients Eat Less but Do Not Eat Differently

BACKGROUND

Lack of robust research methodology for assessing ingestive behavior has impeded clarification of the mediators of food intake following gastric bypass (GBP) surgery.

OBJECTIVES

To evaluate changes in directly measured 24-h energy intake (EI), energy density (ED) (primary outcomes), eating patterns, and food preferences (secondary outcomes) in patients and time-matched weight-stable comparator participants.

METHODS

Patients [n = 31, 77% female, BMI (in kg/m²) 45.5 ± 1.3] and comparators (n = 32, 47% female, BMI 27.2 ± 0.8) were assessed for 36 h under fully residential conditions at baseline (1 mo presurgery) and at 3 and 12 mo postsurgery. Participants had ad libitum access to a personalized menu (n = 54 foods) based on a 6-macronutrient mix paradigm. Food preferences were assessed by the Leeds Food Preference Questionnaire. Body composition was measured by whole-body DXA.

RESULTS

In the comparator group, there was an increase in relative fat intake at 3 mo postsurgery; otherwise, no changes were observed in food intake or body composition. At 12 mo postsurgery, patients lost 27.7 ± 1.6% of initial body weight (P < 0.001). The decline in EI at 3 mo postsurgery (-44% from baseline, P < 0.001) was followed by a partial rebound at 12 mo (-18% from baseline), but at both times, dietary ED and relative macronutrient intake remained constant. The decline in EI was due to eating the same foods as consumed presurgery and by decreasing the size (g, MJ), but not the number, of eating occasions. In patients, reduction in explicit liking at 3 mo (-11.56 ± 4.67, P = 0.007) and implicit wanting at 3 (-15.75 ± 7.76, P = 0.01) and 12 mo (-15.18 ± 6.52, P = 0.022) for sweet foods were not matched by reduced intake of these foods. Patients with the greatest reduction in ED postsurgery reduced both EI and preference for sweet foods.

CONCLUSIONS

After GBP, patients continue to eat the same foods but in smaller amounts. These findings challenge prevailing views about the dynamics of food intake following GBP surgery. This trial was registered as clinicaltrials.gov as NCT03113305.

Early Postoperative Exposure to High-Fat Diet Does Not Increase Long-Term Weight Loss or Fat Avoidance After Roux-en-Y Gastric Bypass in Rats

Background

Bariatric surgery alters food preferences in rats and reportedly decreases desire to consume high-fat high-sugar food in humans. The aim of this study was to investigate whether early post-operative exposure to high-fat food could increase body weight loss after Roux-en-Y gastric bypass (RYGB) by triggering fat avoidance.

Methods

Male Wistar rats underwent either RYGB (n = 15) or sham-operations (n = 16). Preoperatively a standardized 4-choice cafeteria diet [dietary options: low-fat/low-sugar (LFLS), low-fat/high-sugar (LFHS), high-fat/low-sugar (HFLS), high-fat/high-sugar (HFHS)] was offered. First, each option was available for 4 days, thereafter rats were offered the 4 options simultaneously for 3 days preoperatively. Post-surgery, 8 rats in the RYGB- and 8 in the sham-group were exposed to a high-fat content diet (Oatmeal + 30% lard, OM+L) for 10 days, while 7 RYGB rats and 8 sham-rats received OM alone. From the 11th postoperative day, the 4-choice cafeteria diet was reintroduced for 55-days. The intake of all available food items, macronutrients and body weight changes were monitored over 8 weeks. Main outcomes were long-term body-weight and daily change in relative caloric intake during the postoperative cafeteria period compared to the preoperative cafeteria.

Results

During the first 12 days of postoperative cafeteria access, RYGB-rats exposed to OM+L had a higher mean caloric intake per day than RYGB rats exposed to OM alone (Δ10 kCal, P_adj = 0.004), but this difference between the RYGB groups disappeared thereafter. Consequently, in the last 33 days of the postoperative cafeteria diet, the mean body weight of the RYGB+OM+L group was higher compared to RYGB+OM (Δ51 g, P_adj < 0.001). RYGB rats, independently from the nutritional intervention, presented a progressive decrease in daily consumption of calories from fat and increased their daily energy intake mainly from non-sugar carbohydrates. No such differences were detected in sham-operated controls exposed to low- or high fat postoperative interventions.

Conclusion

A progressive decrease in daily fat intake over time was observed after RYGB, independently from the nutritional intervention. This finding confirms that macronutrient preferences undergo progressive changes over time after RYGB and supports the role of ingestive adaptation and learning. Early postoperative exposure to high-fat food failed to accentuate fat avoidance and did not lead to superior weight loss in the long-term.

Oromotor and somatic taste reactivity during sucrose meals reveals internal state and stimulus palatability after gastric bypass in rats

After Roux-en-Y gastric bypass (RYGB), rats consume less high-energy foods and fluids, though whether this reflects a concomitant change in palatability remains unclear. By measuring behavior during intraorally delivered liquid meals across days (1 water, 8 sucrose sessions), we showed that RYGB rats (RYGB, n = 8/sex) consumed less 1.0 M sucrose than their sham surgery counterparts (SHAM, n = 8 males, n = 11 females) but displayed similarly high levels of ingestive taste reactivity responses at the start of infusions. Relative to water, both groups increased intake of sucrose, and ingestive responses were dominated by tongue protrusions rather than mouth movements. Thus, RYGB animals still found sucrose palatable despite consuming less than the SHAM group. As the intraoral infusion progressed but before meal termination, aversive behavior remained low and both RYGB and SHAM animals showed fewer ingestive responses, predominantly mouth movements as opposed to tongue protrusions. This shift in responsiveness unrelated to surgical manipulation suggests negative alliesthesia, or a decreased palatability, as rats approach satiation. Notably, only in RYGB rats, across sessions, there was a striking emergence of aversive behavior immediately after the sucrose meal. Thus, although lower intake in RYGB rats seems independent of the hedonic taste properties of sucrose, taste reactivity behavior in these animals immediately after termination of a liquid meal appears to be influenced by postoral events and reflects a state of nimiety or excessive consumption. Measurement of taste reactivity behaviors during an intraorally delivered meal represents a promising way to make inferences about internal state in nonverbal preclinical models.

The Effects of Roux-en-Y Gastric Bypass on Glucose- vs. Fructose-Associated Conditioned Flavor Preference

In rodents, repeated single-bottle exposures to distinctly flavored isocaloric glucose and fructose solutions, two sugars with different metabolic pathways, eventually lead to a preference for the former. Because Roux-en-Y gastric bypass (RYGB) surgery decreases preference for and intake of sugar solutions in rats, we tested whether RYGB would curtail the conditioning of a preference for a glucose-paired vs. fructose-paired flavor. RYGB (♂ n=11; ♀ n=10) and sham-operated (SHAM; ♂ n=9; ♀ n=10) rats were trained with a single bottle (30 min/day) containing 8% glucose solution flavored with either 0.05% grape or cherry Kool-Aid (Glu/CS^G) or 8% fructose solution with the alternative Kool-Aid flavor (Fru/CS^F) in an alternating fashion for 8 days. To determine baseline preferences, a 4-day 30-min two-bottle test was used to assess preference for Glu/CS^G vs. Fru/CS^F before training. After training, 2-day 30-min two-bottle tests assessed preference for the a) Glu/CS^G (CS^G-flavored 8% glucose solution) vs Fru/CS^F (CS^F-flavored 8% fructose solution), b) CS^G- vs. CS^F-flavored mixture of 4% glucose & 4% fructose (isocaloric), c) CS^G- vs. CS^F-flavored 0.2% saccharin ("sweet", no calories), and d) CS^G- vs. CS^F-flavored water. During training, only male SHAM rats demonstrated progressively increased intake of Glu/CS^G over Fru/CS^F, and female SHAM rats displayed a trend. RYGB eliminated any difference in single-bottle intake of these solutions during training, regardless of sex. Like their male and female SHAM counterparts, male RYGB rats displayed a conditioned preference for the CS^G-associated stimulus in Tests 1-3. Although female RYGB rats displayed acquisition of the conditioned flavor preference in Test 1, unlike the other groups, when the differential sugar cue between the two solutions was removed in Tests 2 and 3, female rats did not display a CS^G preference. When the sugar and sweetener cues were both removed on Test 4, all groups displayed some generalization decrement. Thus, RYGB does not compromise the ability of rats to learn and express a glucose- vs. fructose-associated conditioned flavor preference when the exact CS used in training is presented in testing. The mechanistic basis for the sex difference in the effect of RYGB on the generalization decrement observed in this type of flavor preference learning warrants further study.

Mechanisms of Weight Loss After Obesity Surgery

Obesity surgery remains the most effective treatment for obesity and its complications. Weight loss was initially attributed to decreased energy absorption from the gut but has since been linked to reduced appetitive behavior and potentially increased energy expenditure. Implicated mechanisms associating rearrangement of the gastrointestinal tract with these metabolic outcomes include central appetite control, release of gut peptides, change in microbiota, and bile acids. However, the exact combination and timing of signals remain largely unknown. In this review, we survey recent research investigating these mechanisms, and seek to provide insights on unanswered questions over how weight loss is achieved following bariatric surgery which may eventually lead to safer, nonsurgical weight-loss interventions or combinations of medications with surgery.

Evaluation of the impact of gastric bypass surgery on eating behaviour using objective methodologies under residential conditions: Rationale and study protocol

Gastric bypass surgery leads to significant and sustained weight loss and a reduction in associated health risks in individuals with severe obesity. While reduced energy intake (EI) is the primary driver of weight loss following surgery, the underlying mechanisms accounting for this energy deficit are not well understood. The evidence base has been constrained by a lack of fit-for-purpose methodology in assessing food intake coupled with follow-up studies that are relatively short-term. This paper describes the underlying rationale and protocol for an observational, fully residential study using covert, objective methodology to evaluate changes in 24-hr food intake in patients (n = 31) at 1-month pre-surgery and 3-, 12- and 24-months post-surgery, compared to weight-stable controls (n = 32). The main study endpoints included change in EI, macronutrient intake, food preferences, and eating behaviours (speed, frequency, and duration of eating). Other physiological changes that may influence EI and weight regulation including changes in body composition, circulating appetite hormones, resting metabolic rate, total energy expenditure and gastrointestinal symptoms were also evaluated. Understanding which mechanisms contribute to a reduction in EI and weight loss post-surgery could potentially help to identify those individuals who are most likely to benefit from gastric bypass surgery as well as those that may need more targeted intervention to optimise their weight loss post-surgery. Furthermore, clarification of these mechanisms may also inform targeted approaches for non-surgical treatments of obesity.

One Year Follow-Up of Taste-Related Reward Associations with Weight Loss Suggests a Critical Time to Mitigate Weight Regain Following Bariatric Surgery

Background: Weight regain is a concerning issue in bariatric patients. We previously demonstrated that taste-related reward processing was associated with six-month weight loss outcomes following Roux-en-Y gastric bypass (RYGB) but not vertical sleeve gastrectomy (VSG). Here, we assessed whether these taste factors persisted in predicting weight loss, and weight regain, at one year post-surgery. Methods: Adult women enrolled in a longitudinal study of taste preferences following bariatric surgery completed behavioral and neuroimaging assessments at one year post-surgery. Results: RYGB produced better weight loss relative to VSG, with weight regain and greater weight loss variability observed from six months to one year post-VSG. Changes in liking for high fat at 2 weeks post-surgery from baseline remained a predictor of weight loss in RYGB, but other predictors did not persist. Average liking ratings rebounded to baseline and higher self-reported food cravings and dietary disinhibition correlated with poorer weight loss at one year post-surgery. Conclusion: Initial anatomical and metabolic changes resulting from RYGB that reset neural processing of reward stimuli in the mesolimbic pathway appear to be temporary and may be contingent upon post-operative eating behaviors returning to preoperative obesogenic tendencies. Six months post-surgery may be a critical window for implementing interventions to mitigate weight gain.

A Comparison of Total Food Intake at a Personalised Buffet in People with Obesity, before and 24 Months after Roux-en-Y-Gastric Bypass Surgery

Long-term reductions in the quantity of food consumed, and a shift in intake away from energy dense foods have both been implicated in the potent bariatric effects of Roux-en-Y gastric bypass (RYGB) surgery. We hypothesised that relative to pre-operative assessment, a stereotypical shift to lower intake would be observed at a personalised ad libitum buffet meal 24 months after RYGB, driven in part by decreased selection of high energy density items. At pre-operative baseline, participants (n = 14) rated their preference for 72 individual food items, each of these mapping to one of six categories encompassing high and low-fat choices in combination with sugar, complex carbohydrate or and protein. An 18-item buffet meal was created for each participant based on expressed preferences. Overall energy intake was reduced on average by 60% at the 24-month buffet meal. Reductions in intake were seen across all six food categories. Decreases in the overall intake of all individual macronutrient groups were marked and were generally proportional to reductions in total caloric intake. Patterns of preference and intake, both at baseline and at follow-up appear more idiosyncratic than has been previously suggested by verbal reporting. The data emphasise the consistency with which reductions in ad libitum food intake occur as a sequel of RYGB, this being maintained in the setting of a self-selected ad libitum buffet meal. Exploratory analysis of the data also supports prior reports of a possible relative increase in the proportional intake of protein after RYGB.

Meal Patterns and Food Choices of Female Rats Fed a Cafeteria-Style Diet Are Altered by Gastric Bypass Surgery

After Roux-en-Y gastric bypass surgery (RYGB), rats tend to reduce consumption of high-sugar and/or high-fat foods over time. Here, we sought to investigate the behavioral mechanisms underlying these intake outcomes. Adult female rats were provided a cafeteria diet comprised of five palatable foodstuffs varying in sugar and fat content and intake was monitored continuously. Rats were then assigned to either RYGB, or one of two control (CTL) groups: sham surgery or a nonsurgical control group receiving the same prophylactic iron treatments as RYGB rats. Post-sur-gically, all rats consumed a large first meal of the cafeteria diet. After the first meal, RYGB rats reduced intake primarily by decreasing the meal sizes relative to CTL rats, ate meals more slowly, and displayed altered nycthemeral timing of intake yielding more daytime meals and fewer nighttime meals. Collectively, these meal patterns indicate that despite being motivated to consume a cafeteria diet after RYGB, rats rapidly learn to modify eating behaviors to consume foods more slowly across the entire day. RYGB rats also altered food preferences, but more slowly than the changes in meal patterns, and ate proportionally more energy from complex carbohydrates and protein and proportionally less fat. Overall, the pattern of results suggests that after RYGB rats quickly learn to adjust their size, eating rate, and distribution of meals without altering meal number and to shift their macronutrient intake away from fat; these changes appear to be more related to postingestive events than to a fundamental decline in the palatability of food choices.

Does FGF21 Mediate the Potential Decrease in Sweet Food Intake and Preference Following Bariatric Surgery?

The liver-derived hormone fibroblast growth factor 21 (FGF21) has recently been linked to preference for sweet-tasting food. We hypothesized, that surgery-induced changes in FGF21 could mediate the reduction in sweet food intake and preference following bariatric surgery. Forty participants (35 females) with severe obesity (BMI ≥ 35 kg/m²) scheduled for roux-en-y gastric bypass (n = 30) or sleeve gastrectomy (n = 10) were included. Pre- and postprandial responses of intact plasma FGF21 as well as intake of sweet-tasting food assessed at a buffet meal test, the hedonic evaluation of sweet taste assessed using an apple juice with added sucrose and visual analog scales, and sweet taste sensitivity were assessed before and 6 months after bariatric surgery. In a cross-sectional analysis pre-surgery, pre- and postprandial intact FGF21 levels were negatively associated with the hedonic evaluation of a high-sucrose juice sample (p = 0.03 and p = 0.02). However, no changes in pre- (p = 0.24) or postprandial intact FGF21 levels were found 6 months after surgery (p = 0.11), and individual pre- to postoperative changes in pre- and postprandial intact FGF21 levels were not found to be associated with changes in intake of sweet foods, the hedonic evaluation of sweet taste or sweet taste sensitivity (all p ≥ 0.10). In conclusion, we were not able to show an effect of bariatric surgery on circulating FGF21, and individual postoperative changes in FGF21 were not found to mediate an effect of surgery on sweet food intake and preference.

A systematic review and meta-analyses of food preference modifications after bariatric surgery

This systematic review and meta-analyses aimed to synthesize evidence of the link between bariatric surgery and changes in food preferences, considering the method of assessment. MEDLINE, Cochrane Library, Web of Science, Cinahl, PsychINFO, ProQuest, and Open grey were searched incorporating two blocks of terms ("Intervention" and "Food Preferences"). Interventional or observational studies involving patients (BMI ≥ 35 kg m^-2 ) with sleeve gastrectomy (SG) or Roux-en-Y Gastric Bypass (RYGB) and a control group were included. Meta-analyses were performed comparing the standardized daily mean percentage energy from proteins, carbohydrates, and lipids between preoperative and postoperative patients. Fifty-seven studies concerning 2,271 patients with RYGB and 903 patients with SG met the inclusion criteria, of which 24 were eligible for meta-analysis. Despite a total reduction in macronutrient intakes, the meta-analyses revealed a postoperative increase in percentage energy from proteins at 12 months (0.24, 95% CI: 0.03, 0.46, {I² } = 73%) and a decrease in percentage energy from fat at 1 month (-0.47, 95% CI: 0.86, 0.09, {I² } = 72%), up to 24 months (-0.20, 95% CI: -0.31, 0.08, {I² } = 0%). In conclusion, the present systematic review and meta-analyses showed changes of food preferences in terms of macronutrient, food selection and, overall food appreciation up to 5 years following bariatric surgery.

Microstructural changes in human ingestive behavior after Roux-en-Y gastric bypass during liquid meals

BACKGROUND

Roux-en-Y gastric bypass (RYGB) decreases energy intake and is, therefore, an effective treatment of obesity. The behavioral bases of the decreased calorie intake remain to be elucidated. We applied the methodology of microstructural analysis of meal intake to establish the behavioral features of ingestion in an effort to discern the various controls of feeding as a function of RYGB.

METHODS

The ingestive microstructure of a standardized liquid meal in a cohort of 11 RYGB patients, in 10 patients with obesity, and in 10 healthy-weight adults was prospectively assessed from baseline to 1 year with a custom-designed drinkometer. Statistics were performed on log-transformed ratios of change from baseline so that each participant served as their own control, and proportional increases and decreases were numerically symmetrical. Data-driven (3 seconds) and additional burst pause criteria (1 and 5 seconds) were used.

RESULTS

At baseline, the mean meal size (909.2 versus 557.6 kCal), burst size (28.8 versus 17.6 mL), and meal duration (433 versus 381 seconds) differed between RYGB patients and healthy-weight controls, whereas suck volume (5.2 versus 4.6 mL) and number of bursts (19.7 versus 20.1) were comparable. At 1 year, the ingestive differences between the RYGB and healthy-weight groups disappeared due to significantly decreased burst size (P = 0.008) and meal duration (P = 0.034) after RYGB. The first-minute intake also decreased after RYGB (P = 0.022).

CONCLUSION

RYGB induced dynamic changes in ingestive behavior over the first postoperative year. While the eating pattern of controls remained stable, RYGB patients reduced their meal size by decreasing burst size and meal duration, suggesting that increased postingestive sensibility may mediate postbariatric ingestive behavior.

TRIAL REGISTRATION

NCT03747445; https://clinicaltrials.gov/ct2/show/NCT03747445.

FUNDING

This work was supported by the University of Zurich, the Swiss National Fund (32003B_182309), and the Olga Mayenfisch Foundation. Bálint File was supported by the Hungarian Brain Research Program Grant (grant no. 2017-1.2.1-NKP-2017-00002).

Methodological issues in assessing change in dietary intake and appetite following gastric bypass surgery: A systematic review

Gastric bypass surgery is an effective long-term treatment for individuals with severe obesity. Changes in appetite, dietary intake, and food preferences have all been postulated to contribute to postoperative body weight regulation, however, findings are inconsistent. The aim of this systematic review was to evaluate the current literature on changes in dietary intake and appetite following gastric bypass surgery, in the context of the methodology used and the analysis, interpretation, and presentation of results. Four databases were systematically searched with terms related to "gastric bypass surgery," "appetite," and "dietary intake," and 49 papers (n = 2384 patients after gastric bypass) were eligible for inclusion. The evidence indicated that only a reduction in overall energy intake and an increase in postprandial satiety are maintained beyond 6-month post-surgery, whereas relative macronutrient intake and premeal hunger remain unchanged. However, available data were limited by inconsistencies in the methods, analysis, presentation, and interpretation of results. In particular, there was a reliance on data collected by subjective methods with minimal acknowledgment of the limitations, such as misreporting of food intake. There is a need for further work employing objective measurement of appetite and dietary intake following gastric bypass surgery to determine how these mechanisms may contribute to weight regulation in the longer term.

Factors Associated with Favorable Changes in Food Preferences After Bariatric Surgery

PURPOSE

Bariatric surgery may shift food preferences towards less energy-dense foods. Eating behavior is multifactorial, and the mechanisms driving changes in food preferences could be a combination of a physiological response to surgery and social and psychological factors. This exploratory study aimed to identify potential factors explaining the variation in changes in food preferences after bariatric surgery.

MATERIALS AND METHODS

Physiological, social, and psychological data were collected before, 6 weeks or 6 months after surgery. All variables were analyzed in combination using LASSO regression to explain the variation in changes in energy density at an ad libitum buffet meal 6 months after bariatric surgery (n=39).

RESULTS

The following factors explained 69% of the variation in changes in food preferences after surgery and were associated with more favorable changes in food preferences (i.e., a larger decrease in energy density): female gender, increased secretion of glicentin, a larger decrease in the hedonic rating of sweet and fat and a fatty cocoa drink, a lower number of recent life crises, a low degree of social eating pressure, fulfilling the diagnostic criteria for binge eating disorder, less effort needed to obtain preoperative weight loss, a smaller household composition, a lower degree of self-efficacy and a higher degree of depression, nutritional regime competence, and psychosocial risk level.

CONCLUSION

Factors explaining the variation in altered food preferences after bariatric surgery not only include a physiological response to surgery but also social and psychological factors.

Food Preferences and Their Perceived Changes Before and After Bariatric Surgery: a Cross-sectional Study

PURPOSE

Changes in food preferences, taste, and smell following bariatric surgery have been previously described but with inconsistent results. We aimed to describe current food preferences and their perceived changes before and after the surgery. We further compared food preferences between patients with and without taste or smell alterations, before and above 2 years follow-up, and concerning the success or failure of their surgery.

MATERIALS AND METHODS

This cross-sectional study was conducted with a self-administered online questionnaire. Two years was the cut-off between short- and long-term follow-up. Success was defined as an excess weight loss (EWL) greater or equal to 50%.

RESULTS

In total, 220 postoperative patients answered the questionnaire. Patients with taste alterations (64%) had significantly lower preferences for red meat, milk, cheese, desserts, fried foods, and water (all p < 0.05) relative to the non-taste alteration group, while those with smell alterations (38%) had significantly lower preference for cheese only (p < 0.05) relative to the non-smell alteration group. Patients with a ≥ 2-year follow-up had a higher liking for desserts, fried foods, fat, bread, hot drinks, and alcohol compared to patients with a < 2-year follow-up (all p < 0.05). Patients having success in surgery had higher liking scores for green vegetables and lower liking scores for starchy foods, milk, and sweet dairy products (all p < 0.05).

CONCLUSIONS

Our study suggests that patients who underwent bariatric surgery have different food preference patterns according to their sensory perceptions, the duration of their follow-up, and the success of bariatric surgery.

Orosensory Perception of Fat/Sweet Stimuli and Appetite-Regulating Peptides before and after Sleeve Gastrectomy or Gastric Bypass in Adult Women with Obesity

The aim of this study was to explore the impact of bariatric surgery on fat and sweet taste perceptions and to determine the possible correlations with gut appetite-regulating peptides and subjective food sensations. Women suffering from severe obesity (BMI > 35 kg/m²) were studied 2 weeks before and 6 months after a vertical sleeve gastrectomy (VSG, n = 32) or a Roux-en-Y gastric bypass (RYGB, n = 12). Linoleic acid (LA) and sucrose perception thresholds were determined using the three-alternative forced-choice procedure, gut hormones were assayed before and after a test meal and subjective changes in oral food sensations were self-reported using a standardized questionnaire. Despite a global positive effect of both surgeries on the reported gustatory sensations, a change in the taste sensitivity was only found after RYGB for LA. However, the fat and sweet taste perceptions were not homogenous between patients who underwent the same surgery procedure, suggesting the existence of two subgroups: patients with and without taste improvement. These gustatory changes were not correlated to the surgery-mediated modifications of the main gut appetite-regulating hormones. Collectively these data highlight the complexity of relationships between bariatric surgery and taste sensitivity and suggest that VSG and RYGB might impact the fatty taste perception differently.

Taste-related reward is associated with weight loss following bariatric surgery

BACKGROUNDBariatric surgeries are the most effective treatments for successful and sustained weight loss, but individuals vary in treatment response. Understanding the neurobiological and behavioral mechanisms accounting for this variation could lead to the development of personalized therapeutic approaches and improve treatment outcomes. The primary objectives of this study were to investigate changes in taste preferences and taste-induced brain responses after Roux-en-Y gastric bypass (RYGB) and vertical sleeve gastrectomy (VSG) and to identify potential taste-related predictors of weight loss.METHODSFemales, ages 18 to 55, with a body mass index greater than or equal to 35 kg/m2, and approved for bariatric surgery at the Johns Hopkins Center for Bariatric Surgery were recruited for participation. Demographics, anthropometrics, liking ratings, and neural responses to varying concentrations of sucrose plus fat mixtures were assessed before and after surgery via visual analog scales and functional MRI.RESULTSBariatric surgery produced decreases in liking for sucrose-sweetened mixtures. Greater preference for sucrose-sweetened mixtures before surgery was associated with greater weight loss in RYGB, but not VSG. In the RYGB group only, individuals who showed lower taste-induced activation in the ventral tegmental area (VTA) before surgery and greater changes in taste-induced VTA activation 2 weeks following surgery experienced increased weight loss.CONCLUSIONThe anatomical and/or metabolic changes associated with RYGB may more effectively "reset" the neural processing of reward stimuli, thereby rescuing the blunted activation in the mesolimbic pathway found in patients with obesity. Further, these findings suggest that RYGB may be particularly effective in patients with a preference for sweet foods.FUNDINGNIH K23DK100559 and Dalio Philanthropies.

Physical Activity, Sedentary Behavior, and Sleep Before and After Bariatric Surgery and Associations with Weight Loss Outcome

PURPOSE

Physical activity, sedentary behavior, and sleep have been linked to the likelihood of maintaining healthy body weight. This study aimed to determine objectively measured movement behaviors before and up to 18 months after bariatric surgery and to investigate whether preoperative levels of these movement behaviors and potential changes of these behaviors were associated with changes in body weight and boy composition.

MATERIALS AND METHODS

Accelerometer determined total physical activity, moderate-to-vigorous physical activity (MVPA), light physical activity, sedentary behavior, and sleep (for six consecutive days and seven nights) were assessed approximately 3 months and 1-2 weeks before surgery as well as 6 and 18 months after surgery (n = 41). Body weight and body composition (waist circumference, fat mass, and fat-free mass) were determined at each visit.

RESULTS

Mean weight loss 18 months after surgery was 42.0 ± 1.9 kg. There were no pre- to postoperative improvements in physical activity, sedentary behavior, or sleep. However, greater increases in levels of total physical activity and time spent in MVPA from 3 months before to 6 months after surgery predicted better weight loss and larger reductions in fat mass and waist circumference. Unexpectedly, a lower level of physical activity and a higher level of sedentary behavior before surgery predicted better weight loss outcomes.

CONCLUSION

Objectively measured movement behaviors do not improve after bariatric surgery despite a substantial weight loss. However, increasing total physical activity and/or more time spent in MVPA after surgery may increase weight loss and lead to favorable changes in body composition.

The Preoperative Dietary Inflammatory Index Predicts Changes in Cardiometabolic Risk Factors After 12 Months of Roux-en-Y Gastric Bypass

BACKGROUND

The objective of this study was to evaluate Dietary Inflammatory Index (DII®) in the preoperative period as well as 3 and 12 months post-surgery and its association with cardiometabolic risk factors after RYGB.

MATERIALS AND METHODS

This is a prospective cohort study of 50 patients (both sexes) who underwent RYGB. All data were collected in 3 phases: before surgery, 3, and 12 months post-surgery. To calculate DII scores, we utilized mean nutrients from three 24-h recalls at each time point.

RESULTS

The patients had median age of 39.1 ± 7.9 years (70% women). Mean preoperative DII® score of 0.39 ± 1.49 was slightly pro-inflammatory. Mean DII score reduced to - 1.52 ± 1.27 after 3 months post-surgery and was classified anti-inflammatory. This value rebounded to - 0.88 ± 1.49 at 12 months but was still anti-inflammatory. From the adjusted linear regression analysis, we observed that preoperative DII score was statistically associated with variations in neck circumference (β = - 0.50; p = 0.03), waist-hip ratio (β = 0.01; p = 0.02), total cholesterol (β = 6.47; p = 0.002), and LDL cholesterol (β = 6.42; p = 0.001) after 12 months post-surgery. Changes in DII® at 3 and 12 months were not associated with changes in cardiometabolic risk factors.

CONCLUSION

We observe significant changes in the inflammation potential of diet after 3 and 12 months of RYGB. Patients with higher preoperative E-DII scores have a greater metabolic improvement after 12 months of surgery.

Oral Hydration, Food Intake, and Nutritional Status Before and After Bariatric Surgery

BACKGROUND AND AIMS

Bariatric surgery is considered to be the most effective treatment of morbid obesity. Sleeve gastrectomy (SG) and Roux-en-Y gastric bypass (RYGBP) are the most popular procedures. We evaluated nutritional status, micro- and macronutrient intake, and oral hydration in patients before and regularly during 1 year after RYGBP and SG.

METHODS

All patients that had been through bariatric surgery with at least 1-year post-surgery were retrospectively included in the study. All participants were evaluated once during the 2 months before the surgery and at 1, 3, 6, and 12 months after surgery. Clinical and biological evaluations as well as dietary investigations were performed.

RESULTS

Fifty-seven patients were included in this study (28 RYGBP and 29 SG). Patients in the RYGBP group had significantly higher body weight (132.3 ± 22 versus 122.2 ± 22.2 kg, p = 0.039) than patients in the SG group. Before surgery, total energy intake, oral hydration, and vitamin and mineral intakes were not different between the two groups. RYGBP and SG induced significant similar excess weight loss 1 year after surgery, 48.6 29.8% and 57.6 27.6% of body weight respectively. Energy intake significantly decreased 1 month after surgery and slightly increased from 1 to 12 months without reaching baseline intake levels. Macronutrient repartition did not change during follow-up. Oral hydration significantly decreased after RYGBP (- 58%) and showed a trend to be decreased after SG (- 49%). Sixty-five percent of patients still had vitamin D deficiency 1 year after surgery. Whatever the type of surgery, more than 20% had some vitamin deficiency 1 month after surgery.

CONCLUSIONS

Calories intake decreases after bariatric surgery, whatever the type of procedure. In addition, the prevalence of vitamin deficiency is high after bariatric surgery. Lastly, oral hydration is importantly decreased after bariatric surgery, especially after RYGBP.

Gastric bypass in female rats lowers concentrated sugar solution intake and preference without affecting brief-access licking after long-term sugar exposure

In rodents, Roux-en-Y gastric bypass (RYGB) decreases intake of, and preference for, foods or fluids that are high in sugar. Whether these surgically induced changes are due to decreases in the palatability of sugar stimuli is controversial. We used RYGB and sham-operated (SHAM) female rats to test the influence of prolonged ingestive experience with sugar solutions on the motivational potency of these stimuli to drive licking in brief-access (BA) tests. In experiment 1, RYGB attenuated intake of, and caloric preference for, 0.3 M sucrose during five consecutive, 46-h two-bottle tests (TBTs; sucrose). A second series of TBTs (5 consecutive, 46-h tests) with 1.0 M sucrose revealed similar results, except fluid preference for 1.0 M sucrose also significantly decreased. Before, between, and after the two series of TBTs, two sessions of BA tests (30 min; 10-s trials) with an array of sucrose concentrations (0 and 0.01-1.0 M) were conducted. Concentration-dependent licking and overall trial initiation did not differ between surgical groups in any test. In a similar experimental design in a second cohort of female rats, 0.6 and 2.0 M glucose (isocaloric with sucrose concentrations in experiment 1) were used in the TBTs; 0 and 0.06-2.0 M glucose were used in the BA tests. Outcomes were similar to those for experiment 1, except RYGB rats initiated fewer trials during the BA tests. Although RYGB profoundly affected intake of, and caloric preference for, sugar solutions and, with high concentrations, fluid preference, RYGB never influenced the motivational potency of sucrose or glucose to drive concentration-dependent licking in BA tests.

Predictors of weight loss after bariatric surgery-a cross-disciplinary approach combining physiological, social, and psychological measures

BACKGROUND

Bariatric surgery leads to a substantial weight loss (WL), however, a subset of patients undergoing surgery fails to achieve adequate WL. The reason for the individual variation in WL remains unexplained. Using an exploratory cross-disciplinary approach, we aimed to identify preoperative and early postoperative factors explaining the variation in WL after bariatric surgery.

METHODS

Sixty-one subjects were recruited. Eighteen subjects did not receive surgery and three subjects dropped out, leaving a total sample of 40 subjects. Physiological, social, and psychological data were collected before and 6 months after surgery. All variables were analyzed in combination using a least absolute shrinkage and selection operator (LASSO) regression to explain the variation in WL 18 months after Roux-en-Y gastric bypass (n = 30) and sleeve gastrectomy (n = 10).

RESULTS

Mean WL was 31% (range: 10-52%). The following preoperative factors predicted 59% of the variation in WL: type of surgery (14%), diabetes status (12%), economic resources (9%), sex (7%), binge eating disorder (7%), degree of depression (5%), household type (3%), and physical activity (1%). Including information on early responses after surgery increased the ability to predict WL to 78% and was explained by early WL (47%), changes in energy density of food consumed from a buffet meal (9%), changes in glicentin (5%), degree of depression (5%), sex (5%), type of surgery (2%), economic resources (2%), and changes in drive for thinness (1%).

CONCLUSIONS

Using a cross-disciplinary approach, a substantial part of the individual variation in WL was explained by a combination of basic patient characteristics, psychological profile, and social conditions as well as physiological, psychological and behavioral responses to surgery. These results suggest that patient characteristics collected in a cross-disciplinary approach may help determine predictors for less successful WL after bariatric surgery. If verified in larger cohorts this may form the basis for individualized postoperative support to optimize WL outcome.

Oxyntomodulin and Glicentin May Predict the Effect of Bariatric Surgery on Food Preferences and Weight Loss

BACKGROUND

Alterations in several gastrointestinal hormones are implicated in the postoperative suppression of food intake leading to weight loss after Roux-en-Y gastric bypass (RYGB) and sleeve gastrectomy (SG). The aim was to evaluate changes in responses of gastrointestinal hormones after RYGB and SG and the associations of these changes with weight loss, energy intake, and food preferences.

METHODS

Forty-two subjects with severe obesity were included (32 RYGB; 10 SG). Postprandial responses of glicentin, oxyntomodulin, glucagon-like peptide-1 (GLP-1), peptide YY (PYY), and ghrelin were measured before and 6 months after surgery. Energy intake and energy density were assessed before and 6 months after surgery using a buffet meal test and weight loss was assessed 18 months after surgery.

RESULTS

Postprandial concentrations of glicentin, oxyntomodulin, GLP-1, and ghrelin differed between RYGB and SG (all P ≤ .02). Enhanced responses of glicentin and oxyntomodulin predicted a greater weight loss (both P < .01) and were associated with a larger decrease in energy density (P ≤ .04). No associations were found for GLP-1, PYY, and ghrelin, and changes were not associated with changes in energy intake. When combing all hormones, 60%, 19%, and 33% of the variations in weight loss, energy intake, and energy density, respectively, could be explained.

CONCLUSION

Postprandial responses of gastrointestinal hormones differed between RYGB and SG. Enhanced responses of glicentin and oxyntomodulin predicted a better weight loss and were associated with a decreased preference for energy-dense foods. Replication of these results could imply an opportunity to identify patients in need of additional support after surgical treatments of obesity.

A Randomized, Placebo-Controlled Double-Blind Trial of a Closed-Loop Glucagon System for Postbariatric Hypoglycemia

BACKGROUND

Postbariatric hypoglycemia (PBH) can threaten safety and reduce quality of life. Current therapies are incompletely effective.

METHODS

Patients with PBH were enrolled in a double-blind, placebo-controlled, crossover trial to evaluate a closed-loop glucose-responsive automated glucagon delivery system designed to reduce severe hypoglycemia. A hypoglycemia detection and mitigation algorithm was embedded in the artificial pancreas system connected to a continuous glucose monitor (CGM, Dexcom) driving a patch infusion pump (Insulet) filled with liquid investigational glucagon (Xeris) or placebo (vehicle). Sensor/plasma glucose responses to mixed meal were assessed during 2 study visits. The system delivered up to 2 doses of study drug (300/150 μg glucagon or equal-volume vehicle) if triggered by the algorithm. Rescue dextrose was given for plasma glucose <55 mg/dL or neuroglycopenia.

RESULTS

Twelve participants (11 females/1 male, age 52 ± 2, 8 ± 1 years postsurgery, mean ± SEM) completed all visits. Predictive hypoglycemia alerts prompted automated drug delivery postmeal, when sensor glucose was 114 ± 7 vs 121 ± 5 mg/dL (P = .39). Seven participants required rescue glucose after vehicle but not glucagon (P = .008). Five participants had severe hypoglycemia (<55 mg/dL) after vehicle but not glucagon (P = .03). Nadir plasma glucose was higher with glucagon vs vehicle (67 ± 3 vs 59 ± 2 mg/dL, P = .004). Plasma glucagon rose after glucagon delivery (1231 ± 187 vs 16 ± 1 pg/mL at 30 minutes, P = .001). No rebound hyperglycemia occurred. Transient infusion site discomfort was reported with both glucagon (n = 11/12) and vehicle (n = 10/12). No other adverse events were observed.

CONCLUSION

A CGM-guided closed-loop rescue system can detect imminent hypoglycemia and deliver glucagon, reducing severe hypoglycemia in PBH.

CLINICAL TRIALS REGISTRATION

NCT03255629.

Comparison of Energy and Food Intake Between Gastric Bypass and Sleeve Gastrectomy: a Meta-analysis and Systematic Review

AbstractObesity is a developed nutritional problem, and today, surgery is one of the approaches to cure it. A good understanding of the variations in food intake will be beneficial for sustaining long-term weight loss post-surgery and for improving nutrition care strategies. The purpose of this review was the comparison of the impact of two methods of gastric bypass (GBP) and sleeve gastrectomy (SG) on dietary intake. Databases of PubMed, Embase, Scopus, Google Scholar, and Web of science were used for the literature search up to June 2018. We concluded the studies that measured mean daily energy intake and the percent of macronutrients from total calorie intake of before and after GBP and SG. A total of 18 studies were finally included in the meta-analysis for the effect of bariatric surgery on food intake. Bariatric surgery significantly decreased energy intake by 1050.04 kcal/day (p < 0.001) compared with the baseline values of energy intake. The pooled effect of bariatric surgery on protein intake was 0.82 g/day (p = 0.004) compared with the baseline values. The pooled analysis found no significant impact of bariatric surgery on carbohydrate intake (WMD = 0.56 g/day; p = 0.40) compared with the baseline values. The pooled estimate of effect for bariatric surgery on fat intake was - 1.34 g/day (p = 0.006). This study demonstrates that bariatric surgery might be effective on energy and fat intake; however, there was no effect on carbohydrate intake.

Bariatric Surgery Leads to Short-Term Effects on Sweet Taste Sensitivity and Hedonic Evaluation of Fatty Food Stimuli

OBJECTIVE

The aim of this study was to investigate the effect of bariatric surgery on sweet taste sensitivity and the hedonic evaluation of sweet, savory, and fatty food stimuli as well as associations with weight loss and food preferences assessed at a buffet meal test.

METHODS

The detection and recognition threshold for sweet taste and the hedonic rating of sweet, savory, and fatty food stimuli were assessed before and after a preoperative diet-induced weight loss and 6 weeks, 6 months, and 18 months after Roux-en-Y gastric bypass (RYGB) and sleeve gastrectomy (SG) (n = 29).

RESULTS

The detection threshold for sweet taste decreased after the diet-induced weight loss and 6 weeks after RYGB (both P ≤ 0.03). The hedonic rating of high-fat food stimuli decreased 6 weeks after RYGB and SG (all P ≤ 0.02). Changes in the hedonic rating of high-fat food stimuli were associated with increased preferences for high-fat foods at the buffet meal (P = 0.03) and tended to be associated with weight loss (P = 0.05). No changes were detected for sweet and savory food stimuli.

CONCLUSIONS

RYGB increased sweet taste sensitivity; however, this effect was already seen after the diet-induced weight-loss. RYGB and SG decreased the hedonic evaluation of high-fat food stimuli, but this effect did not translate into decreased preferences for high-fat food.

Preoperative liking and wanting for sweet beverages as predictors of body weight loss after Roux-en-Y gastric bypass and sleeve gastrectomy

Background/objectives:

Patients who receive Roux-en-Y gastric bypass (RYGB) lose more weight than those who receive vertical sleeve gastrectomy (VSG). RYGB and VSG alter hedonic responses to sweet flavor, but whether baseline differences in hedonic responses modulate weight loss after RYGB or VSG remains untested.

Participants/methods:

Male and female candidates (n=66) for RYGB or VSG were recruited and tested for their subjective liking and wanting ratings of sucrose solutions and flavored beverages sweetened with aspartame. Participants were classified by unsupervised hierarchical clustering for their liking and wanting ratings of sucrose and aspartame. Participant liking ratings were also used in a supervised classification using pre-established categories of liking ratings (liker, disliker, and inverted u-shape). Effects of categories obtained from unsupervised or supervised classification on body weight loss and their interaction with surgery type were analyzed separately at 3 and 12 months after surgery using linear models corrected for sex and age.

Results:

RYGB participants lost more body weight compared to VSG participants at 3 and 12 months after surgery (P < 0.001 for both time points). Unsupervised clustering analysis identified clusters corresponding to high and low wanting or liking ratings for sucrose or aspartame. RYGB participants in high-wanting clusters based on sucrose, but not aspartame, lost more weight than VSG at both 3 (P = 0.01) and 12 months (P = 0.03), yielding a significant cluster by surgery interaction. Categories based on supervised classification using liking ratings for sucrose or aspartame showed no significant effects on body weight loss between RYGB and VSG participants.

Conclusions:

Classification of patients into high/low wanting ratings for sucrose before surgery can predict differential body weight loss after RYGB or VSG in adults and could be used to advise on surgery type.

RYGB and flavor-consequence learning

Flavor-consequence learning refers to learned associations between flavor stimuli and post-oral consequences of food that affect food selection, amount eaten and affect. Forms of flavor-consequence learning include flavor aversions, flavor avoidance, conditioned satiety, expected satiety and appetition. Roux-en-Y gastric bypass surgery (RYGB) and other bariatric procedures alter gastrointestinal processing of food in a number of ways. Thus, it is plausible that these procedures alter post-oral unconditioned stimuli that support flavor-consequence learning, leading to altered food selection, amount eaten, and affect. Surprisingly, however, there is almost no research on the role of flavor-consequence learning in the effects of bariatric surgery on appetite. This issue urgently warrants investigation.

Phosphatidylcholine and its relation to apolipoproteins A-1 and B changes after Roux-en-Y gastric bypass: a cohort study

Background

Phosphatidylcholine (PC), the most abundant of the phospholipids, has several metabolic functions in organs such as the liver and the intestine, important structural- and signaling functions in biological membranes, and might have a role in the effects of Roux-en-Y gastric bypass (RYGB), an operation known to ameliorate metabolic diseases, including type 2 diabetes. We hypothesized that serum PC, as a reflection of phospholipid metabolism, changes after RYGB, and that changes are related to weight loss and possibly to changes in glucose metabolism (reflected in the HbA1c-level) as well as to changes in serum Apo A1, Apo B and Apo B/Apo A1 ratio.

Methods

In a cohort of 220 RYGB patients, we studied changes in serum PC after RYGB in relation to serum Apo A1 and Apo B, the main apolipoproteins in HDL- and LDL/VLDL-particles, respectively, up to 2 years following RYGB-surgery.

Results

Serum PC reached its lowest levels 3 months postoperatively to later rebound to preoperative levels 24 months after RYGB. No difference was seen between patients with or without type 2 diabetes. Serum Apo A1 showed a similar pattern whereas serum Apo B concentrations stayed low after the initial decrease after RYGB. As a result, the Apo B / Apo A1 ratio constantly decreased during follow-up. There was a strong positive correlation between PC and Apo A1, and between PC and Apo B, but none between Apo A1 and Apo B. After RYGB surgery, both PC and Apo A1, but not Apo B, correlated positively to weight loss. In relation to total cholesterol, the molar ratio between serum PC and plasma cholesterol increased steadily after RYGB.

Conclusions

We conclude that changes in PC and apolipoproteins after RYGB are highly dynamic, reflecting a large plasticity and capability of accommodating lipid metabolism including PC-, cholesterol- and apolipoprotein metabolism imposed by RYGB surgery, independent of glucose tolerance. We suggest that after RYGB and major weight loss, PC and Apo A1 might have a special role in the altered metabolism of lipoproteins.

Electronic supplementary material

The online version of this article (10.1186/s12944-019-1111-7) contains supplementary material, which is available to authorized users.

Effects of Roux-en-Y Gastric Bypass and Sleeve Gastrectomy on Food Preferences and Potential Mechanisms Involved

PURPOSE OF REVIEW

Bariatric surgery leads to a substantial decrease in energy intake. It is unclear whether this decrease in energy intake is simply due to eating smaller portions of the same food items or a shift in food preference towards less energy-dense foods. This review evaluates the existing literature on changes in food preferences after bariatric surgery and the potential mechanisms involved.

RECENT FINDINGS

Changes in food preferences have been reported; however, the evidence is mainly based on indirect measurements, such as self-reporting. When changes in food preferences are directly assessed, results contradict previous findings, indicating that results based on self-reporting must be interpreted with caution as they do not necessarily reflect actual behaviour. However, it seems that there could be inter-individual differences in the response to surgery. Future studies investigating changes in food preferences should not only focus on direct measured of behaviour but should also consider the heterogeneity of the response after bariatric surgery.

Changes in taste function and ingestive behavior following bariatric surgery

Bariatric surgery is the most effective treatment for severe obesity and its related comorbidities. Roux-en-Y Gastric Bypass (RYGB) and Sleeve Gastrectomy (SG) are currently the most popular weight-loss surgeries used worldwide. Following these surgeries, many patients self-report changes in taste perception and decreased preference for unhealthy foods. These reported changes might account for increased adherence to healthier diets and successful weight loss after surgeries. However, researchers have used a variety of methodologies to assess patients' reported changes andresults are discrepant. The goal of this review is to summarize the literature regarding changes to taste function and ingestive behavior following RYGB and SG to examine differences in findings by methodology (indirect vs. direct measurements). We focused our review around changes in sweets, fats, and alcohol because most of the documented changes in ingestive behavior post-surgery are related to changes in these dietary items. We found that studies using surveys and questionnaires generally find that subjects self-report changes in taste and decrease their preference and cravings for energy-dense foods (particularly, sweets and high-fats). However, studies using validated sensory techniques that include oral sampling or by using direct food intake measurements find little to no change in subjects' ability to perceive taste or their preference for energy-dense foods. Therefore, reported changes in taste and food preferences are unlikely to be explained by alterations in taste intensity and diet selection, and are rather related to changes in the rewarding value of food. Further, that RYGB, and likely SG, is associated with increased alcohol consumption and arisk to develop an alcohol use disorder) supports the notion that these surgeries alter central circuits of reward that are critical in the regulation of ingestive behavior.

Taste- and flavor-guided behaviors following Roux-en-Y gastric bypass in rodent models

Roux-en-Y gastric bypass (RYGB) surgery is one of the most efficacious treatments for obesity, but the behavioral and physiological mechanisms through which it enacts its effects are not completely understood. The weight loss that follows RYGB surgery is due to some extent to decreased caloric intake. The perception of flavor and the sense of taste undoubtedly contribute to ingestion, and changes in taste sensation and flavor perception may, even in part, propel the altered feeding seen after RYGB surgery. Measuring observable behavior in non-human animal models of RYGB surgery is an objective way by which to evaluate underlying mechanism, including the influence of flavor and taste to intake changes after RYGB surgery, as well as the interaction of flavor and taste with post-oral consequences and learning phenomena. Collectively, the data in rodent models support the conclusion that neither palatability nor motivational potency are reduced following RYGB surgery. Indeed, rats still typically show preference for sweet and fatty solids and liquids, and positive flavor-guided hedonic responses for these substances remain stable in some tests. However, preference for these foods and fluids is reduced, and flavor-guided behaviors after long-term tests are reorganized. These patterns suggest that, while rats are still motivated to consume sweet and fatty consumables and find them palatable, they learn to limit their intake of them to avoid undesirable post-oral consequences. Examination of these interactions and elucidating their physiologic correlates may maximize the efficacy of RYGB surgery and/or promote the development of alternative or supplemental treatments.

Associations between Weight Loss, Food Likes, Dietary Behaviors, and Chemosensory Function in Bariatric Surgery: A Case-Control Analysis in Women

We tested the hypothesis that successful weight loss post-bariatric surgery would be associated with healthier chemosensory function, food likes, and dietary behaviors than either unsuccessful weight loss or pre-surgery morbid obesity. In a case-control design, pre-surgical women with morbid obesity (n = 49) were compared with those 1-year post-surgery (24 Roux-en-Y Bypass, 24 Sleeve Gastrectomy) and defined by excess or percent weight loss as successful/unsuccessful. For self-reported smell/taste perception, more post-surgery than pre-surgery reported improved/distorted perception, especially if weight loss successful. Measured taste function (perceived quinine and NaCl intensity) was lower among weight loss unsuccessful versus pre-surgery patients, yet a genetic variation in taste probe (propylthiouracil bitterness) matched expected frequencies without significant pre/post-surgery difference. Regarding survey-reported liking, higher diet quality was seen in the weight loss successful (independent of surgery type) versus pre-surgical patients, with differences driven by lower sweet and refined carbohydrate liking. The post versus pre-surgical patients had greater restraint but less hunger and disinhibition. Patients reporting both higher diet quality and lower hunger showed greater % weight loss, independent of surgery type. Thus, successful weight loss 1-year post-bariatric surgery was associated with improved or distorted chemosensation and patterns of liking associated with healthier diets, especially if coupled with less hunger.

Comparison of surgical versus diet-induced weight loss on appetite regulation and metabolic health outcomes

Bariatric surgery is associated with significant and sustained weight loss and improved metabolic outcomes. It is unclear if weight loss alone is the main mechanism of improved metabolic health. The purpose of this trial was to compare indices of appetite regulation, insulin sensitivity and energy intake (EI) between participants achieving 10 kg of weight loss via Roux-en-Y Gastric Bypass (RYGB) or dietary restriction (DIET); intake of a very low calorie liquid diet (800 kcal/d; 40% protein, 40% fat, 20% carbohydrate that matched the post-RYGB dietary protocol). Adults qualifying for bariatric surgery were studied before and after 10 kg of weight loss (RYGB [n = 6]) or DIET [n = 17]). Appetite (hunger, satiety, and prospective food consumption [PFC]), appetite-related hormones, and metabolites (ghrelin, PYY, GLP-1, insulin, glucose, free fatty acids [FFA], and triglycerides [TG]) were measured in the fasting state and every 30 min for 180 min following breakfast. Participants were provided lunch to evaluate acute ad libitum EI, which was similarly reduced in both groups from pre to post weight loss. Fasting ghrelin was reduced to a greater extent following RYGB compared to DIET (P = 0.04). Area under the curve (AUC) for ghrelin (P = 0.01), hunger (P < 0.01) and PFC (P < 0.01) increased after DIET compared to RYGB, following 10 kg weight loss. Satiety AUC increased after RYGB and decreased after DIET (P < 0.01). Glucose and insulin (fasting and AUC) decreased in both groups. FFA increased in both groups, with a greater increase in AUC seen after RYGB versus DIET (P = 0.02). In summary, appetite-related indices were altered in a manner that, if maintained, may promote a sustained reduction in energy intake with RYGB compared to DIET. Future work with a larger sample size and longer follow-up will be important to confirm and extend these findings.

Proceedings from the 2018 Association for Chemoreception Annual Meeting Symposium: Bariatric Surgery and Its Effects on Taste and Food Selection

This article provides a summary of the topics discussed at the symposium titled "Bariatric Surgery and Its Effects on Taste and Food Selection," which was held at the Fortieth Annual Meeting of the Association for Chemoreception Sciences. Bariatric surgery such as Roux-en-Y gastric bypass (RYGB) is currently one of the most effective treatments available for weight loss and Type 2 diabetes. For this reason, it is of great interest to clinicians as well as to basic scientists studying the controls of feeding and energy balance. Despite the commonly held view by clinicians that RYGB patients change their food preferences away from fats and sugars in favor of less energy dense alternatives such as vegetables, the empirical support for this claim is equivocal. It is currently thought that the taste and palatability of fats and sugars are affected by the surgery. Some key preclinical and clinical findings addressing these issues were evaluated in this symposium.