Recent Advances in the Neurobiology of Altered Motivation Following Bariatric Surgery

Hedonic hunger, eating behavior, and food reward and preferences 1 year after initial weight loss by diet or bariatric surgery

OBJECTIVE

The objective of this study was to investigate changes in hedonic hunger, eating behavior, and food reward and preferences at 1-year (1Y) follow-up after an initial weight loss (WL) induced by a 10-week, very low-energy diet alone (controls) or in combination with bariatric surgery.

METHODS

Patients scheduled for sleeve gastrectomy or Roux-en-Y gastric bypass and controls were recruited. Body weight/composition, hedonic hunger (Power of Food Scale), eating behavior traits (Dutch Eating Behavior Questionnaire and Three-Factor Eating Questionnaire), and food reward and preferences (computerized behavioral task) were measured at baseline, 11 weeks, and 1Y follow-up.

RESULTS

Changes in anthropometric variables were comparable across groups in the initial phase (week 11), and hedonic hunger decreased overall. The bariatric-surgery groups continued to lose body weight and fat mass, whereas weight regain was seen in controls at 1Y follow-up. Decreases in emotional eating, hunger, disinhibition, and food reward and increases in dietary restraint were seen at 1Y follow-up in the bariatric-surgery groups only.

CONCLUSIONS

Continued WL with bariatric surgery is paralleled by favorable changes in eating behavior and food reward and preferences. By contrast, controls experienced weight regain at 1Y follow-up and no changes in eating behavior. These striking differences are likely to be important in the long-term WL management of individuals with severe obesity.

Bariatric Surgery and New-Onset Substance Use Disorders: A Systematic review and Meta-analysis

Increasing evidence suggests that bariatric surgery (BS) patients are at risk for substance abuse disorders (SUD). The purpose of this systematic review and meta-analysis was to determine the relationship between BS and the development of new-onset substance abuse disorder (SUDNO) in bariatric patients. On October 31, 2023, we reviewed the scientific literature following PRISMA guidelines. A total of 3242 studies were analyzed, 7 met the inclusion criteria. The pooled incidence of SUDNO was 4.28%. Patients' characteristics associated with SUDNO included preoperative mental disorders, high pre-BS BMI, and public health insurance. Surgical factors associated with new SUDNOs included severe complications in the peri- or postoperative period. The occurrence of SUDNOs is a non-negligeable complication after BS. Predisposing factors may be identified and preventive actions undertaken.

Transcranial Magnetic Stimulation for Reducing the Relative Reinforcing Value of Food in Adult Patients With Obesity Pursuing Metabolic and Bariatric Surgery: Protocol for a Pilot, Within-Participants, Sham-Controlled Trial

BACKGROUND

Metabolic and bariatric surgery (MBS) is the most effective and durable obesity treatment. However, there is heterogeneity in weight outcomes, which is partially attributed to variability in appetite and eating regulation. Patients with a strong desire to eat in response to the reward of palatable foods are more likely to overeat and experience suboptimal outcomes. This subgroup, classified as at risk, may benefit from repetitive transcranial magnetic stimulation (rTMS), a noninvasive brain stimulation technique that shows promise for reducing cravings and consumption of addictive drugs and food; no study has evaluated how rTMS affects the reinforcing value of food and brain reward processing in the context of MBS.

OBJECTIVE

The goal of the Transcranial Magnetic Stimulation to Reduce the Relative Reinforcing Value of Food (RESTRAIN) study is to perform an initial rTMS test on the relative reinforcing value (RRV) of food (the reinforcing value of palatable food compared with money) among adult patients who are pursuing MBS and report high food reinforcement. Using a within-participants sham-controlled crossover design, we will compare the active and sham rTMS conditions on pre- to posttest changes in the RRV of food (primary objective) and the neural modulation of reward, measured via electroencephalography (EEG; secondary objective). We hypothesize that participants will show larger decreases in food reinforcement and increases in brain reward processing after active versus sham rTMS.

METHODS

Participants (n=10) will attend 2 study sessions separated by a washout period. They will be randomized to active rTMS on 1 day and sham rTMS on the other day using a counterbalanced schedule. For both sessions, participants will arrive fasted in the morning and consume a standardized breakfast before being assessed on the RRV of food and reward tasks via EEG before and after rTMS of the left dorsolateral prefrontal cortex.

RESULTS

Recruitment and data collection began in December 2022. As of October 2023, overall, 52 patients have been screened; 36 (69%) screened eligible, and 17 (47%) were enrolled. Of these 17 patients, 3 (18%) were excluded before rTMS, 5 (29%) withdrew, 4 (24%) are in the process of completing the protocol, and 5 (29%) completed the protocol.

CONCLUSIONS

The RESTRAIN study is the first to test whether rTMS can target neural reward circuits to reduce behavioral (RRV) and neural (EEG) measures of food reward in patients who are pursuing MBS. If successful, the results would provide a rationale for a fully powered trial to examine whether rTMS-related changes in food reinforcement translate into healthier eating patterns and improved MBS outcomes. If the results do not support our hypotheses, we will continue this line of research to evaluate whether additional rTMS sessions and pulses as well as different stimulation locations produce clinically meaningful changes in food reinforcement.

TRIAL REGISTRATION

ClinicalTrials.gov NCT05522803; https://clinicaltrials.gov/study/NCT05522803.

INTERNATIONAL REGISTERED REPORT IDENTIFIER (IRRID)

DERR1-10.2196/50714.

Incidence of Substance Use Disorder Following Bariatric Surgery: A Retrospective Cohort Study

BACKGROUND

New-onset substance use disorder (SUD) following bariatric surgery is a significant concern that is likely multi-factorial, although the etiologies are unclear. Previous studies have identified variable rates of SUD along with utilizing different methods and measures. The objective of this study is to evaluate new-onset SUD diagnoses among adults following bariatric surgery and compare these rates to those in the general population as well as those diagnosed with overweight or obesity.

METHODS

Data was extracted from TriNetX Research Platform and used to build three cohorts of adults: those who had bariatric surgery (bariatric surgery cohort), those diagnosed with obesity or overweight, and a general population cohort. Rates of incident SUD were compared among these three groups. Initial encounters for all individuals were from January 1, 2018, to June 30, 2019.

RESULTS

The incidence rate of SUD in patients with a history of bariatric surgery was 6.55% (n = 2523). When compared to the general population, persons who had any type of bariatric procedure had a decreased risk of new-onset SUD with an overall odds ratio (OR) [95% confidence limits (CL)] of 0.89 [0.86, 0.93]. When compared to persons with overweight or obesity, bariatric patients were less likely to develop any form of SUD (OR: 0.65 [0.62, 0.67]).

CONCLUSION

While overall rates of new-onset SUD are lower among those who had bariatric surgery, they also vary by surgery and substance type. Efforts should still be made to address new-onset SUD in order to optimize the post-surgical care of patients.

Opioid prescribing practices following bariatric surgery: a systematic review and pooled proportion meta-analysis

INTRODUCTION

A paucity of literature exists regarding current opioid prescribing and use following bariatric surgery. We aimed to characterize opioid prescribing practices and use following bariatric surgery to inform future studies and optimized prescribing practices.

METHODS AND PROCEDURE

We performed a systematic review of Ovid MEDLINE, Ovid Embase, Scopus, Web of Science Core Collection, and Cochrane Library (via WILEY) on August 20, 2021. Two reviewers reviewed and extracted data independently. Studies evaluating adult patients undergoing bariatric surgery that reported opioid prescriptions at discharge were included. Abstracts, non-English studies, and those with n < 5 were excluded. Primary outcomes assessed the amount of morphine milligram equivalents (MMEs) prescribed at discharge. Secondary outcomes evaluated opioids used following discharge, proportion of patients with unused opioid, and if unused opioids were properly discarded.

RESULTS

We evaluated 2113 studies, with 18 undergoing full-text review, and 5 meeting inclusion criteria. Overall, 847 patients were included, with 450 (53%) undergoing sleeve gastrectomy and 393 (46%) receiving Roux-en-Y gastric bypass. Most patients were female (n = 484/589, 82.2%), and the average age and BMI were 44.6 (± 11.8) years and 48.1 kg/m² (± 8.4 kg/m²), respectively. On average, 348.4 MMEs were prescribed to patients undergoing bariatric surgery. Patients used only 84.7 MMEs, with 87.0% (95% CI 66.0-99.0%) having unused opioid, and 41/120 (34.2%) retaining these excess opioids.

CONCLUSION

Nearly 90% of all bariatric patients evaluated in our systematic review are prescribed excessive opioids at discharge. Further work characterizing current opioid prescribing practices and use may help guide development of standardized post-bariatric surgery prescription guidelines.

New persistent opioid use after bariatric surgery: a systematic review and pooled proportion meta-analysis

INTRODUCTION

Increasing evidence suggests surgical patients are at risk for developing new, persistent opioid use (NPOU) following surgery. This risk may be heightened for patients undergoing bariatric surgery. Few studies have evaluated this important long-term outcome and little is known about the rate of NPOU, or factors associated with NPOU for bariatric surgery patients.

METHODS AND PROCEDURE

We conducted a systematic review of MEDLINE, Embase, Scopus, Web of Science, and Cochrane databases in August 2021. Studies were reviewed and data extracted independently by two reviewers following MOOSE guidelines. Studies evaluating bariatric surgery patients reporting NPOU, defined as new opioid use > 90 days after surgery, were included. Abstracts, non-English, animal, n < 5, and pediatric studies were excluded. Primary outcome was NPOU prevalence, and secondary outcomes were patient and surgical factors associated with NPOU. Factors associated with NPOU are reported from findings of individual studies; meta-analysis could not be completed due to heterogeneity of reporting.

RESULTS

We retrieved a total of 2113 studies with 8 meeting inclusion criteria. In studies reporting NPOU rates (n = 4 studies), pooled prevalence was 6.0% (95% CI 4.0-7.0%). Patient characteristics reported by studies to be associated with NPOU included prior substance use (tobacco, alcohol, other prescription analgesics), preoperative mental health disorder (anxiety, mood disorders, eating disorders), and public health insurance. Surgical factors associated with NPOU included severe post-operative complications and in-hospital opioid use (peri- or post operatively).

CONCLUSIONS

NPOU is an uncommon but important complication following bariatric surgery, with patient factors including prior substance abuse, mental health disorders, and use of public health insurance placing patients at increased risk, and surgical factors being complications and peri-operative opioid use. Studies evaluating techniques to reduce NPOU in these high-risk populations are needed.

Involvement of Helicobacter pylori in Preoperative Gastric Findings on a Bariatric Population

The prevalence of Helicobacter pylori (Hp) in bariatric patients is common and related to gastric pathology. With preoperative upper gastrointestinal endoscopy (UGE), these pathologies and the presence of Hp are diagnosed. The histopathological study of the UGE biopsies is classified based on the Sydney System, a scoring system that stages chronic gastritis (CG) and precancerous gastric lesions. The objective is to assess the histological findings of gastric biopsies during routine UGE and to determine the involvement of Hp in gastric disorders in patients undergoing bariatric surgery. A multicenter retrospective review of prospectively collected databases was performed. The presence of CG, gastric atrophy (GA), and gastric intestinal metaplasia (GIM) in the study of the biopsies was assessed and correlated with Hp infection. The incidence of Hp among our bariatric population was 36.1%, and it increases with age. The percentage of patients with severe Hp infection is higher in patients with GA or GIM. The Hp eradication rate is also reduced when GA and GIM are present. A histological examination of all the biopsies did not show features of malignancy in any of the cases. Hp is not the only factor involved in the development of gastric pathology in bariatric patients.

Effects of bariatric surgery on functional connectivity of the reward and default mode network: A pre-registered analysis

Obesity imposes serious health risks and involves alterations in resting‐state functional connectivity of brain networks involved in eating behavior. Bariatric surgery is an effective treatment, but its effects on functional connectivity are still under debate. In this pre‐registered study, we aimed to determine the effects of bariatric surgery on major resting‐state brain networks (reward and default mode network) in a longitudinal controlled design. Thirty‐three bariatric surgery patients and 15 obese waiting‐list control patients underwent magnetic resonance imaging at baseline, after 6 and 12 months. We conducted a pre‐registered whole‐brain time‐by‐group interaction analysis, and a time‐by‐group interaction analysis on within‐network connectivity. In exploratory analyses, we investigated the effects of weight loss and head motion. Bariatric surgery compared to waiting did not significantly affect functional connectivity of the reward network and the default mode network (FWE‐corrected p > .05), neither whole‐brain nor within‐network. In exploratory analyses, surgery‐related BMI decrease (FWE‐corrected p = .041) and higher average head motion (FWE‐corrected p = .021) resulted in significantly stronger connectivity of the reward network with medial posterior frontal regions. This pre‐registered well‐controlled study did not support a strong effect of bariatric surgery, compared to waiting, on major resting‐state brain networks after 6 months. Exploratory analyses indicated that head motion might have confounded the effects. Data pooling and more rigorous control of within‐scanner head motion during data acquisition are needed to substantiate effects of bariatric surgery on brain organization.

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.