Neural predictors of 12-month weight loss outcomes following bariatric surgery

A systematic review and meta-analysis combining adolescent and adult data to evaluate weight loss and the effect of age following the laparoscopic sleeve gastrectomy

Obesity is a grave concern within the United States, resulting in lost productivity, increased medical costs, and comorbidities with lifelong repercussions. The laparoscopic sleeve gastrectomy is a treatment option for obesity. The following meta-analysis sought to combine adolescent and adult literature to determine the overall effect of the sleeve gastrectomy on weight loss, to evaluate the effect of age at the time of surgery on weight loss, and to describe and explore variation in weight loss by sample characteristics. Overall weight loss was assessed at proximal and distal points, a dichotomous moderator variable analysis was conducted with subjects ≤21 years of age and >21 years of age, and a meta-regression assessing % male, % female, and baseline BMI was conducted to assess moderator variables. The laparoscopic sleeve gastrectomy was effective at facilitating weight loss with effect sizes varying from 0.916 to2.816. Age, biological sex, and baseline BMI were not found to have an impact on weight loss. The clinical consequences of prolonged obesity are evident and earlier intervention may be justified to counter the long-term effects caused by obesity related comorbidities. Standardized reporting of comorbidities and the effect of bariatric surgery on comorbid conditions is essential to allow further analysis.

The effect of weight loss on hypothalamus structure and function in obese individuals: a systematic review and meta-analysis

INTRODUCTION

Obesity presents with structural and functional hypothalamic dysfunction. However, it is unclear whether weight loss can lead to hypothalamic changes. We therefore aimed to conduct a systematic review and meta-analysis to determine the effect of body mass reduction in obese individuals on hypothalamic structure and function.

METHODS

PubMed, Embase and Cochrane databases were searched for studies that reported the change in hypothalamic structure and function after weight loss. Qualitative and quantitative analyses were performed on magnetic resonance imaging techniques, medio-basal hypothalamus T2-relaxation time, blood oxygen level dependent (BOLD) contrast, voxel-based morphometry (VBM) and biomarkers including glucose, insulin, leptin, ghrelin and inflammatory markers of interleukins. Mean differences between pre- and post-weight loss and 95% confidence intervals (CIs) were pooled using random-effects models.

RESULTS

Thirteen pre-post studies were included, of which six accounted for the meta-analysis. Studies showed a favorable decrease in T2-relaxation time (n = 1), favorable change in hypothalamic activity after weight loss on BOLD contrast (n = 4), with higher peak activities after surgical weight loss (n = 2). No differences were found in the gray matter density of the hypothalamus on VBM (n = 1). Pooled mean differences between pre- and post-surgical weight loss revealed a decrease of 8.53 mg/dl (95% CI: 5.17, 11.9) in glucose, 7.73 pmol/l (95% CI: 5.07, 10.4) in insulin, 15.5 ng/ml (95% CI: 9.40, 21.6) in leptin, 142.9 pg/ml (95% CI: 79.0, 206.8) in ghrelin and 9.43 pg/ml (95% CI: -6.89, 25.7) in IL-6 level.

CONCLUSIONS

Our study showed weight reduction in obesity led to limited structural change and significant functional changes in the hypothalamus.

Influence of Bariatric Surgery on Gut Microbiota Composition and Its Implication on Brain and Peripheral Targets

Obesity remains a significant global health challenge, with bariatric surgery remaining as one of the most effective treatments for severe obesity and its related comorbidities. This review highlights the multifaceted impact of bariatric surgery beyond mere physical restriction or nutrient malabsorption, underscoring the importance of the gut microbiome and neurohormonal signals in mediating the profound effects on weight loss and behavior modification. The various bariatric surgery procedures, such as Roux-en-Y gastric bypass (RYGB) and sleeve gastrectomy (SG), act through distinct mechanisms to alter the gut microbiome, subsequently impacting metabolic health, energy balance, and food reward behaviors. Emerging evidence has shown that bariatric surgery induces profound changes in the composition of the gut microbiome, notably altering the Firmicutes/Bacteroidetes ratio and enhancing populations of beneficial bacteria such as Akkermansia. These microbiota shifts have far-reaching effects beyond gut health, influencing dopamine-mediated reward pathways in the brain and modulating the secretion and action of key gut hormones including ghrelin, leptin, GLP-1, PYY, and CCK. The resultant changes in dopamine signaling and hormone levels contribute to reduced hedonic eating, enhanced satiety, and improved metabolic outcomes. Further, post-bariatric surgical effects on satiation targets are in part mediated by metabolic byproducts of gut microbiota like short-chain fatty acids (SCFAs) and bile acids, which play a pivotal role in modulating metabolism and energy expenditure and reducing obesity-associated inflammation, as well as influencing food reward pathways, potentially contributing to the regulation of body weight and reduction in hedonic eating behaviors. Overall, a better understanding of these mechanisms opens the door to developing non-surgical interventions that replicate the beneficial effects of bariatric surgery on the gut microbiome, dopamine signaling, and gut hormone regulation, offering new avenues for obesity treatment.

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.

Application of machine learning algorithms in classifying postoperative success in metabolic bariatric surgery: Acomprehensive study

Objectives

Metabolic bariatric surgery is a critical intervention for patients living with obesity and related health issues. Accurate classification and prediction of patient outcomes are vital for optimizing treatment strategies. This study presents a novel machine learning approach to classify patients in the context of metabolic bariatric surgery, providing insights into the efficacy of different models and variable types.

Methods

Various machine learning models, including Gaussian Naive Bayes, Complement Naive Bayes, K-nearest neighbour, Decision Tree, K-nearest neighbour with RandomOverSampler, and K-nearest neighbour with SMOTE, were applied to a dataset of 73 patients. The dataset, comprising psychometric, socioeconomic, and analytical variables, was analyzed to determine the most efficient predictive model. The study also explored the impact of different variable groupings and oversampling techniques.

Results

Experimental results indicate average accuracy values as high as 66.7% for the best model. Enhanced versions of K-nearest neighbour and Decision Tree, along with variations of K-nearest neighbour such as RandomOverSampler and SMOTE, yielded the best results.

Conclusions

The study unveils a promising avenue for classifying patients in the realm of metabolic bariatric surgery. The results underscore the importance of selecting appropriate variables and employing diverse approaches to achieve optimal performance. The developed system holds potential as a tool to assist healthcare professionals in decision-making, thereby enhancing metabolic bariatric surgery outcomes. These findings lay the groundwork for future collaboration between hospitals and healthcare entities to improve patient care through the utilization of machine learning algorithms. Moreover, the findings suggest room for improvement, potentially achievable with a larger dataset and careful parameter tuning.

Neuroimaging and neuroendocrine insights into food cravings and appetite interventions in obesity

This article reviews the previous studies on the distinction between food cravings and appetite, and how they are regulated by hormones and reflected in brain activity. Based on existing research, food cravings are defined as individual preferences influenced by hormones and psychological factors, which differ from appetite, as they are not necessarily related to hunger or nutritional needs. The article also evaluates the neuroimaging findings about food cravings, and interventions to reduce food cravings, such as mindfulness training, alternative sweeteners, non-invasive brain stimulation techniques, cognitive-behavioral therapy, and imaginal retraining, and points out their advantages, disadvantages, and limitations. Furthermore, the article delves into the potential future directions in the field, emphasizing the need for a neuroendocrine perspective, considerations for associated psychiatric disorders, innovative clinical interventions, and emerging therapeutic frontiers in obesity management. The article outlines the neuro-endocrine basis of food cravings, including ghrelin, leptin, melanocortin, oxytocin, glucagon-like peptide-1, baclofen, and other hormones and their brain regions of action. The article argues that food cravings are an important target for obesity, and more research is needed to explore their complex characteristics and mechanisms, and how to effectively interact with their neuro-endocrine pathways. The article provides a new perspective and approach to the prevention and treatment of obesity.

Towards precision medicine in bariatric surgery prescription

Obesity is a complex, multifactorial and chronic disease. Bariatric surgery is a safe and effective treatment intervention for obesity and obesity-related diseases. However, weight loss after surgery can be highly heterogeneous and is not entirely predictable, particularly in the long-term after intervention. In this review, we present and discuss the available data on patient-related and procedure-related factors that were previously appointed as putative predictors of bariatric surgery outcomes. In addition, we present a critical appraisal of the available evidence on which factors could be taken into account when recommending and deciding which bariatric procedure to perform. Several patient-related features were identified as having a potential impact on weight loss after bariatric surgery, including age, gender, anthropometrics, obesity co-morbidities, eating behavior, genetic background, circulating biomarkers (microRNAs, metabolites and hormones), psychological and socioeconomic factors. However, none of these factors are sufficiently robust to be used as predictive factors. Overall, there is no doubt that before we long for precision medicine, there is the unmet need for a better understanding of the socio-biological drivers of weight gain, weight loss failure and weight-regain after bariatric interventions. Machine learning models targeting preoperative factors and effectiveness measurements of specific bariatric surgery interventions, would enable a more precise identification of the causal links between determinants of weight gain and weight loss. Artificial intelligence algorithms to be used in clinical practice to predict the response to bariatric surgery interventions could then be created, which would ultimately allow to move forward into precision medicine in bariatric surgery prescription.

Factors associated with different patterns of weight change after bariatric surgery: A longitudinal study

Background

The mean weight loss (WL) after successful bariatric surgery is approximately one third of the initial body weight, which is mainly achieved between the first 2 years of follow-up. However, 15%-35% of patients do not achieve a significant percentage of total WL (%TWL). Information on factors associated with a higher or lower WL after bariatric surgery is limited. This study aimed to assess the change in %TWL and describe the factors associated with greater or lesser WL over time.

Methods

This prospective longitudinal study included patients treated with laparoscopic Roux-en-Y gastric bypass or sleeve gastrectomy. Baseline data were recorded before surgery. Follow-up was performed at 3 (n = 141), 6 (n = 208), 9 (n = 115), 12 (n = 216), 24 (n = 166), and 36 months (n = 99). Generalized estimating equation analysis was performed to assess the changes in %TWL over time and factors associated with different patterns of WL.

Results

In total, 231 patients were included (women, 82.2%; basal body mass index (BMI) 41.4 ± 5.1 kg/m2). The tendencies to increase %TWL (32 ± 6.5) were evident in the first year and stabilized thereafter. Sustained nutritionist follow-up (2.3%, p = 0.004), baseline BMI >40 kg/m2 (0.4%, p < 0.001), and WL ≥ 10 kg before surgery (0.3%, p = 0.001) were associated with a higher %TWL. Patients who performed physical activity >30 min/day after surgery reduced their %TWL by 0.6% (p = 0.002).

Conclusions

Modifiable factors such as nutritional monitoring and WL before surgery are associated with a significant increase in %TWL over time. Basal BMI was associated with a significant decrease in %TWL.

Novel Insights into the Physiology of Nutrient Sensing and Gut-Brain Communication in Surgical and Experimental Obesity Therapy

Despite standardized surgical technique and peri-operative care, metabolic outcomes of bariatric surgery are not uniform. Adaptive changes in brain function may play a crucial role in achieving optimal postbariatric weight loss. This review follows the anatomic-physiologic structure of the postbariatric nutrient-gut-brain communication chain through its key stations and provides a concise summary of recent findings in bariatric physiology, with a special focus on the composition of the intestinal milieu, intestinal nutrient sensing, vagal nerve-mediated gastrointestinal satiation signals, circulating hormones and nutrients, as well as descending neural signals from the forebrain. The results of interventional studies using brain or vagal nerve stimulation to induce weight loss are also summarized. Ultimately, suggestions are made for future diagnostic and therapeutic research for the treatment of obesity.

Control of energy homeostasis by the lateral hypothalamic area

The lateral hypothalamic area (LHA) is a subcortical brain region that exerts control over motivated behavior, feeding, and energy balance across species. Recent single-cell sequencing studies have defined at least 30 distinct LHA neuron types. Some of these influence specific aspects of energy homeostasis; however, the functions of many LHA cell types remain unclear. This review addresses the rapidly emerging evidence from cell-type-specific investigations that the LHA leverages distinct neuron populations to regulate energy balance through complex connections with other brain regions. It will highlight recent findings demonstrating that LHA control of energy balance extends beyond mere food intake and propose outstanding questions to be addressed by future research.

Cognitive Control and Weight Loss After Bariatric Surgery: the BARICO Study

BACKGROUND AND OBJECTIVES

Bariatric surgery (BS) is an effective treatment for obesity. However, some individuals experience insufficient weight loss after surgery. Therefore, we investigated whether cognitive control affects weight loss after Roux-en-Y gastric bypass (RYGB).

METHODS

Within this exploratory observational study, part of the BARICO study (BAriatric surgery Rijnstate and Radboudumc neuroImaging and Cognition in Obesity), participants aged between 35 and 55 years eligible for RYGB were included. Before and after BS, body weight, (delta) BMI and percentage total body weight loss (%TBWL) were determined. Additionally, at baseline, Stroop task-performance, -activation and -connectivity were assessed by a color-word paradigm task during functional neuroimaging to determine the ability of participants to inhibit cognitive interference.

RESULTS

Seventy-six participants were included, of whom 14 were excluded from fMRI analysis, leaving 62 participants. Participants were aged 45.0 ± 5.9 years with a mean pre-surgery BMI of 40.2 ± 3.3 kg/m2, and 86% were women. Mean decrease in BMI was 13.8 ± 2.5 kg/m2, and mean %TBWL was 34.9 ± 6.3% 1 year after BS. Stroop task performance did not correlate with (delta) BMI and %TBWL. The inferior parietal/middle occipital gyrus, inferior frontal gyrus, and supplementary motor cortex were involved in cognitive interference, although activity in these regions did not predict weight loss after surgery. Lastly, generalized psychophysiological interaction did not provide evidence for (delta) BMI- and %TBWL-dependent connectivity modulation.

DISCUSSION

Cognitive control did not predict weight loss after surgery. Future studies should focus on longer follow-up periods to understand the relation between cognitive control and weight loss.

TRIAL REGISTRATION

NL7090 ( https://www.clinicaltrialregister.nl/nl/trial/28949 ).

The Neurobiology of Eating Behavior in Obesity: Mechanisms and Therapeutic Targets: A Report from the 23rd Annual Harvard Nutrition Obesity Symposium

Obesity is increasing at an alarming rate. The effectiveness of currently available strategies for the treatment of obesity (including pharmacologic, surgical, and behavioral interventions) is limited. Understanding the neurobiology of appetite and the important drivers of energy intake (EI) can lead to the development of more effective strategies for the prevention and treatment of obesity. Appetite regulation is complex and is influenced by genetic, social, and environmental factors. It is intricately regulated by a complex interplay of endocrine, gastrointestinal, and neural systems. Hormonal and neural signals generated in response to the energy state of the organism and the quality of food eaten are communicated by paracrine, endocrine, and gastrointestinal signals to the nervous system. The central nervous system integrates homeostatic and hedonic signals to regulate appetite. Although there has been an enormous amount of research over many decades regarding the regulation of EI and body weight, research is only now yielding potentially effective treatment strategies for obesity. The purpose of this article is to summarize the key findings presented in June 2022 at the 23rd annual Harvard Nutrition Obesity Symposium entitled "The Neurobiology of Eating Behavior in Obesity: Mechanisms and Therapeutic Targets." Findings presented at the symposium, sponsored by NIH P30 Nutrition Obesity Research Center at Harvard, enhance our current understanding of appetite biology, including innovative techniques used to assess and systematically manipulate critical hedonic processes, which will shape future research and the development of therapeutics for obesity prevention and treatment.

Neural activation of regions involved in food reward and cognitive control in young females with anorexia nervosa and atypical anorexia nervosa versus healthy controls

Anorexia nervosa (AN) and atypical AN (AtypAN) are complex neurobiological illnesses that typically onset in adolescence with an often treatment-refractory and chronic illness trajectory. Aberrant eating behaviors in this population have been linked to abnormalities in food reward and cognitive control, but prior studies have not examined respective contributions of clinical characteristics and metabolic state. Research is needed to identify specific disruptions and inform novel intervention targets to improve outcomes. Fifty-nine females with AN (n = 34) or AtypAN (n = 25), ages 10-22 years, all ≤90% expected body weight, and 34 age-matched healthy controls (HC) completed a well-established neuroimaging food cue paradigm fasting and after a standardized meal, and we used ANCOVA models to investigate main and interaction effects of Group and Appetitive State on blood oxygenation level-dependent (BOLD) activation for the contrast of exposure to high-calorie food images minus objects. We found main effects of Group with greater BOLD activation in the dorsal anterior cingulate cortex (dACC), dorsolateral prefrontal cortex (DLPFC), hippocampus, caudate, and putamen for AN/AtypAN versus HC groups, and in the three-group model including AN, AtypAN, and HC (sub-)groups, where differences were primarily driven by greater activation in the AtypAN subgroup versus HC group. We found a main effect of Appetitive State with increased premeal BOLD activation in the hypothalamus, amygdala, nucleus accumbens, and caudate for models that included AN/AtypAN and HC groups, and in BOLD activation in the nucleus accumbens for the model that included AN, AtypAN, and HC (sub-)groups. There were no interaction effects of Group with Appetitive State for any of the models. Our findings demonstrate robust feeding-state independent group effects reflecting greater neural activation of specific regions typically associated with reward and cognitive control processing across AN and AtypAN relative to healthy individuals in this food cue paradigm. Differential activation of specific brain regions in response to the passive viewing of high-calorie food images may underlie restrictive eating behavior in this clinical population.

Brain functional and structural magnetic resonance imaging of obesity and weight loss interventions

Obesity has tripled over the past 40 years to become a major public health issue, as it is linked with increased mortality and elevated risk for various physical and neuropsychiatric illnesses. Accumulating evidence from neuroimaging studies suggests that obesity negatively affects brain function and structure, especially within fronto-mesolimbic circuitry. Obese individuals show abnormal neural responses to food cues, taste and smell, resting-state activity and functional connectivity, and cognitive tasks including decision-making, inhibitory-control, learning/memory, and attention. In addition, obesity is associated with altered cortical morphometry, a lowered gray/white matter volume, and impaired white matter integrity. Various interventions and treatments including bariatric surgery, the most effective treatment for obesity in clinical practice, as well as dietary, exercise, pharmacological, and neuromodulation interventions such as transcranial direct current stimulation, transcranial magnetic stimulation and neurofeedback have been employed and achieved promising outcomes. These interventions and treatments appear to normalize hyper- and hypoactivations of brain regions involved with reward processing, food-intake control, and cognitive function, and also promote recovery of brain structural abnormalities. This paper provides a comprehensive literature review of the recent neuroimaging advances on the underlying neural mechanisms of both obesity and interventions, in the hope of guiding development of novel and effective treatments.

Regulation of body weight: Lessons learned from bariatric surgery

BACKGROUND

Bariatric or weight loss surgery is currently the most effective treatment for obesity and metabolic disease. Unlike dieting and pharmacology, its beneficial effects are sustained over decades in most patients, and mortality is among the lowest for major surgery. Because there are not nearly enough surgeons to implement bariatric surgery on a global scale, intensive research efforts have begun to identify its mechanisms of action on a molecular level in order to replace surgery with targeted behavioral or pharmacological treatments. To date, however, there is no consensus as to the critical mechanisms involved.

SCOPE OF REVIEW

The purpose of this non-systematic review is to evaluate the existing evidence for specific molecular and inter-organ signaling pathways that play major roles in bariatric surgery-induced weight loss and metabolic benefits, with a focus on Roux-en-Y gastric bypass (RYGB) and vertical sleeve gastrectomy (VSG), in both humans and rodents.

MAJOR CONCLUSIONS

Gut-brain communication and its brain targets of food intake control and energy balance regulation are complex and redundant. Although the relatively young science of bariatric surgery has generated a number of hypotheses, no clear and unique mechanism has yet emerged. It seems increasingly likely that the broad physiological and behavioral effects produced by bariatric surgery do not involve a single mechanism, but rather multiple signaling pathways. Besides a need to improve and better validate surgeries in animals, advanced techniques, including inducible, tissue-specific knockout models, and the use of humanized physiological traits will be necessary. State-of-the-art genetically-guided neural identification techniques should be used to more selectively manipulate function-specific pathways.

Impact of sleeve gastrectomy compared to Roux-en-y gastric bypass upon hedonic hunger and the relationship to post-operative weight loss

'Hedonic hunger' indicates the desire to consume food in the absence of an energy requirement. Hedonic hunger can be investigated using the validated Power of Food Scale (PFS). Roux-en-Y gastric bypass (RYGB) and sleeve gastrectomy (SG) are currently the most effective treatment options for severe obesity. Following RYGB, hedonic hunger diminishes, which may contribute to sustained weight loss. There are no data examining the effect of SG on hedonic hunger. We prospectively evaluated hedonic hunger using PFS in patients with severe obesity prior to and 6 months after SG (n = 95) or RYGB (n = 44) and investigated the procedure-specific relationship between percentage weight loss (%WL) and hedonic hunger. Anthropometric data were collected at baseline after 6 months, 12 months and 24 months post-operatively. PFS contains 15 items grouped into 3 domains considering when food is: available (FA), present (FP), tasted (FT) and a total score (TS). At 6 months, a significant reduction was seen in all categories post-SG (p < 0.0001) and in TS (p = 0.003), FA (p = 0.0006) and FP (p = 0.0007) post-RYGB. A significantly larger reduction in FP scores was seen post-SG (p = 0.01). Post-SG, a significant correlation with 6-month %WL was noted for changes in FP (p = 0.03) and TS (p = 0.03). Post-SG changes in FP and TS predicted 24-month %WL. Post-RYGB significant correlations were seen between 6-month %WL and dFA (p = 0.04) and dFP (p = 0.03). Changes in FA, FP and TS were predictive of 12-month %WL. HH is reduced following both SG and RYGB with a greater reduction following SG and is related to post-operative %WL. PFS may have a role as a predictive tool for post-operative outcomes following SG and RYGB.

Food cue reactivity in successful laparoscopic gastric banding: A sham-deflation-controlled pilot study

Laparoscopic adjustable gastric banding (LAGB) offers a unique opportunity to examine the underlying neuronal mechanisms of surgically assisted weight loss due to its instant, non-invasive, adjustable nature. Six participants with stable excess weight loss (%EWL ≥ 45) completed 2 days of fMRI scanning 1.5-5 years after LAGB surgery. In a within-subject randomized sham-controlled design, participants underwent (sham) removal of ∼ 50% of the band's fluid. Compared to sham-deflation (i.e., normal band constriction) of the band, in the deflation condition (i.e., decreasing restriction) participants showed significantly lower activation in the anterior (para)cingulate, angular gyrus, lateral occipital cortex, and frontal cortex in response to food images (p < 0.05, whole brain TFCE-based FWE corrected). Higher activation in the deflation condition was seen in the fusiform gyrus, inferior temporal gyrus, lingual gyrus, lateral occipital cortex. The findings of this within-subject randomized controlled pilot study suggest that constriction of the stomach through LAGB may indirectly alter brain activation in response to food cues. These neuronal changes may underlie changes in food craving and food preference that support sustained post-surgical weight-loss. Despite the small sample size, this is in agreement with and adds to the growing literature of post-bariatric surgery changes in behavior and control regions.

Computational approaches to predicting treatment response to obesity using neuroimaging

Obesity is a worldwide disease associated with multiple severe adverse consequences and comorbid conditions. While an increased body weight is the defining feature in obesity, etiologies, clinical phenotypes and treatment responses vary between patients. These variations can be observed within individual treatment options which comprise lifestyle interventions, pharmacological treatment, and bariatric surgery. Bariatric surgery can be regarded as the most effective treatment method. However, long-term weight regain is comparably frequent even for this treatment and its application is not without risk. A prognostic tool that would help predict the effectivity of the individual treatment methods in the long term would be essential in a personalized medicine approach. In line with this objective, an increasing number of studies have combined neuroimaging and computational modeling to predict treatment outcome in obesity. In our review, we begin by outlining the central nervous mechanisms measured with neuroimaging in these studies. The mechanisms are primarily related to reward-processing and include "incentive salience" and psychobehavioral control. We then present the diverse neuroimaging methods and computational prediction techniques applied. The studies included in this review provide consistent support for the importance of incentive salience and psychobehavioral control for treatment outcome in obesity. Nevertheless, further studies comprising larger sample sizes and rigorous validation processes are necessary to answer the question of whether or not the approach is sufficiently accurate for clinical real-world application.

Impaired Brain Satiety Responses After Weight Loss in Children With Obesity

CONTEXT

Obesity interventions often result in increased motivation to eat.

OBJECTIVE

We investigated relationships between obesity outcomes and changes in brain activation by visual food cues and hormone levels in response to obesity intervention by family-based behavioral treatment (FBT).

METHODS

Neuroimaging and hormone assessments were conducted before and after 24-week FBT intervention in children with obesity (OB, n = 28), or children of healthy weight without intervention (HW, n = 17), all 9- to 11-year-old boys and girls. We evaluated meal-induced changes in neural activation to high- vs low-calorie food cues across appetite-processing brain regions and gut hormones.

RESULTS

Among children with OB who underwent FBT, greater declines of BMI z-score were associated with lesser reductions after the FBT intervention in meal-induced changes in neural activation to high- vs low-calorie food cues across appetite-processing brain regions (P < 0.05), and the slope of relationship was significantly different compared with children of HW. In children with OB, less reduction in brain responses to a meal from before to after FBT was associated with greater meal-induced reduction in ghrelin and increased meal-induced stimulation in peptide YY and glucagon-like peptide-1 (all P < 0.05).

CONCLUSION

In response to FBT, adaptations of central satiety responses and peripheral satiety-regulating hormones were noted. After weight loss, changes of peripheral hormone secretion support weight loss, but there was a weaker central satiety response. The findings suggest that even when peripheral satiety responses by gut hormones are intact, the central regulation of satiety is disturbed in children with OB who significantly improve their weight status during FBT, which could favor future weight regain.

Behavioral Interventions to Attenuate Driven Overeating and Weight Regain After Bariatric Surgery

Weight regain after bariatric surgery is associated with problematic eating behaviors that have either recurred after a period of improvement or are new-onset behaviors. Problematic eating behaviors after bariatric surgery have been conceptualized in different ways in the literature, such as having a food addiction and experiencing a loss of control of eating. The intersection of these constructs appears to be driven overeating defined as patients' experiences of reduced control of their eating which results in overeating behavior. The purpose of this review is to define patient experiences of driven overeating through the behavioral expression of emotion-based eating, reward-based eating, and executive functioning deficits-namely impulsivity-which is associated with weight regain after having bariatric surgery. Delineating concepts in this way and determining treatment strategies accordingly may reduce distress related to the inevitable return of increased hunger, cravings, portion sizes, and tolerance for highly palatable foods after surgery. Along with standard behavioral weight maintenance strategies, topics including acceptance, motivation, emotion-based eating, reward-based/impulsive eating, physical activity, and self-compassion are discussed. These concepts have been adapted for patients experiencing weight regain after having bariatric surgery and may be particularly helpful in attenuating driven overeating and weight regain.

Brain responses to anticipatory cues and milkshake taste in obesity, and their relationship to bariatric surgery outcome

There is substantial variability in percent total weight loss (%TWL) following bariatric surgery. Functional brain imaging may explain more variance in post-surgical weight loss than psychological or metabolic information. Here we examined the neuronal responses during anticipatory cues and receipt of drops of milkshake in 52 pre-bariatric surgery men and women with severe obesity (OW, BMI = 35-60 kg/m2) (23 sleeve gastrectomy (SG), 24 Roux-en-Y gastric bypass (RYGB), 3 laparoscopic adjustable gastric banding (LAGB), 2 did not undergo surgery) and 21 healthy-weight (HW) controls (BMI = 19-27 kg/m2). One-year post-surgery weight loss ranged from 3.1 to 44.0 TWL%. Compared to HW, OW had a stronger response to milkshake cues (compared to water) in frontal and motor, somatosensory, occipital, and cerebellar regions. Responses to milkshake taste receipt (compared to water) differed from HW in frontal, motor, and supramarginal regions where OW showed more similar response to water. One year post-surgery, responses to high-fat milkshake cues normalized in frontal, motor, and somatosensory regions. This change in brain response was related to scores on a composite health index. We found no correlation between baseline response to milkshake cues or tastes and%TWL at 1-yr post-surgery. In RYGB participants only, a stronger response to low-fat milkshake and water cues (compared to high-fat) in supramarginal and cuneal regions respectively was associated with more weight loss. A stronger cerebellar response to high-fat vs low-fat milkshake receipt was also associated with more weight loss. We confirm differential responses to anticipatory milkshake cues in participants with severe obesity and HW in the largest adult cohort to date. Our brain wide results emphasizes the need to look beyond reward and cognitive control regions. Despite the lack of a correlation with post-surgical weight loss in the entire surgical group, participants who underwent RYGB showed predictive power in several regions and contrasts. Our findings may help in understanding the neuronal mechanisms associated with obesity.

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.

Late bedtime is associated with lower weight loss in patients with severe obesity after sleeve gastrectomy

BACKGROUND

Previous research has shown that sleep can play a role in obesity and weight loss. However, the association of sleep with weight loss in patients with severe obesity after bariatric surgery remains unexplored. We aimed to evaluate the role of sleep in weight loss evolution in a cohort of patients who underwent sleeve gastrectomy.

METHODS

A cohort of 252 patients with severe obesity (75.7% women; age [mean ± SD] 47.7 ± 10.8 years; BMI 44.2 ± 5.9 kg/m²) was followed for 1 year after surgery. Anthropometric, biochemical, physical activity, sleep (bedtime, wakeup time, and sleep duration) and dietary intake variables were collected pre- and post-surgery (1 year). Linear and non-linear regression models were used to examine the associations between sleep variables and weight loss. Participants were grouped into 'early' and 'late' sleepers according to a bedtime threshold (before or after 24:00 h), and the differences in weight loss, physical activity, meal timing, and dietary intake between groups were studied.

RESULTS

1-h increments in bedtime were linearly associated with less excess weight loss (EWL) [-2.23%; 95%CI: -3.37; -0.70; p = 0.005] 1 year after the sleeve gastrectomy. Late sleepers lost less weight (-5.64% of EWL [95%CI: -10.11; -1.17]; p = 0.014) when compared to early sleepers and showed a higher energy intake after 21:00 h (8.66% of total energy intake [95% CI: 4.87; 12.46]; p < 0.001).

CONCLUSIONS

Late bedtime is associated with less success of weight loss 1 year after the sleeve gastrectomy. Late sleepers consumed more of their calories closer to bedtime. Our results highlight the relevance of considering recommendations on bedtime and meal timing for patients after bariatric surgery.

Diets Varying in Carbohydrate Content Differentially Alter Brain Activity in Homeostatic and Reward Regions in Adults

BACKGROUND

Obesity has one of the highest refractory rates of all chronic diseases, in part because weight loss induced by calorie restriction, the first-line treatment for obesity, elicits biological adaptations that promote weight regain. Although acute feeding trials suggest a role for macronutrient composition in modifying brain activity related to hunger and satiety, relevance of these findings to weight-loss maintenance has not been studied.

OBJECTIVES

We investigated effects of weight-loss maintenance diets varying in macronutrient content on regional cerebral blood flow (rCBF) in brain regions involved in hunger and reward.

METHODS

In conjunction with a randomized controlled feeding trial, we investigated the effects of weight-loss maintenance diets varying in carbohydrate content [high, 60% of total energy: n = 20; 6 men/14 women; mean age: 32.5 y; mean BMI (in kg/m 2): 27.4; moderate, 40% of total energy: n = 22; 10 men/12 women; mean age: 32.5 y; mean BMI: 29.0; low, 20% of total energy: n = 28; 12 men/16 women; mean age: 33.2 y; mean BMI: 27.7] on rCBF in brain regions involved in hunger and reward preprandial and 4 h postprandial after 14-20 wk on the diets. The primary outcome was rCBF in the nucleus accumbens (NAcc) at 4 h postprandial; the secondary outcome was preprandial rCBF in the hypothalamus.

RESULTS

Consistent with a priori hypothesis, at 4 h postprandial, NAcc rCBF was 43% higher in adults assigned to the high- compared with low-carbohydrate diet {P[family-wise error (FWE)-corrected] < 0.05}. Preprandial hypothalamus rCBF was 41% higher on high-carbohydrate diet [P(FWE-corrected) < 0.001]. Exploratory analyses revealed that elevated rCBF on high-carbohydrate diet was not specific to prandial state: preprandial NAcc rCBF [P(FWE-corrected) < 0.001] and 4 h postprandial rCBF in hypothalamus [P(FWE-corrected) < 0.001]. Insulin secretion predicted differential postprandial activation of the NAcc by diet.

CONCLUSIONS

We report significant differences in rCBF in adults assigned to diets varying in carbohydrate content for several months, which appear to be partially associated with insulin secretion. These findings suggest that chronic intake of a high-carbohydrate diet may affect brain reward and homeostatic activity in ways that could impede weight-loss maintenance. This trial was registered at clinicaltrials.gov as NCT02300857.

Preoperative brain μ-opioid receptor availability predicts weight development following bariatric surgery in women

Bariatric surgery is the most effective method for weight loss in morbid obesity. There is significant individual variability in the weight loss outcomes, yet factors leading to postoperative weight loss or weight regain remain elusive. Alterations in the μ-opioid receptor (MOR) and dopamine D₂ receptor (D₂R) systems are associated with obesity and appetite control, and the magnitude of initial brain receptor system perturbation may predict long-term surgical weight loss outcomes. We tested this hypothesis by studying 19 morbidly obese women (mean BMI 40) scheduled to undergo bariatric surgery. We measured their preoperative MOR and D₂R availabilities using positron emission tomography with [¹¹C]carfentanil and [¹¹C]raclopride, respectively, and then assessed their weight development association with regional MOR and D₂R availabilities at 24-month follow-up. MOR availability in the amygdala consistently predicted weight development throughout the follow-up period, but no associations were found for D₂R. This is the first study to our knowledge to demonstrate that neuroreceptor markers prior to bariatric surgery are associated with postoperative weight development. Postoperative weight regain may derive from dysfunction in the opioid system, and weight loss outcomes after bariatric surgery may be partially predicted based on preoperative brain receptor availability, opening up new potential for treatment possibilities.

Strategies to Understand the Weight-Reduced State: Genetics and Brain Imaging

Most individuals with obesity or overweight have difficulty maintaining weight loss. The weight-reduced state induces changes in many physiological processes that appear to drive weight regain. Here, we review the use of cell biology, genetics, and imaging techniques that are being used to begin understanding why weight regain is the normal response to dieting. As with obesity itself, weight regain has both genetic and environmental drivers. Genetic drivers for "thinness" and "obesity" largely overlap, but there is evidence for specific genetic loci that are different for each of these weight states. There is only limited information regarding the genetics of weight regain. Currently, most genetic loci related to weight point to the central nervous system as the organ responsible for determining the weight set point. Neuroimaging tools have proved useful in studying the contribution of the central nervous system to the weight-reduced state in humans. Neuroimaging technologies fall into three broad categories: functional, connectivity, and structural neuroimaging. Connectivity and structural imaging techniques offer unique opportunities for testing mechanistic hypotheses about changes in brain function or tissue structure in the weight-reduced state.

Physiology of the Weight-Reduced State: A Report from a National Institute of Diabetes and Digestive and Kidney Diseases Workshop

Preventing regain of lost weight is the most difficult challenge in the treatment of obesity. The National Institute of Diabetes and Digestive and Kidney Diseases convened a workshop, "The Physiology of the Weight-Reduced State," on June 3 to 4, 2019, in order to explore the physiologic mechanisms of appetitive and metabolic adaptation that take place in the weight-reduced state and counter an individual's efforts to maintain reduced weight following weight loss.

Addiction Transfer and Other Behavioral Changes Following Bariatric Surgery

Despite its important treatment implications for obesity and related comorbidities, bariatric surgery requires several behavioral changes that warrant comprehensive evaluation and support before and after surgery. This article outlines emerging scientific and anecdotal evidence for addiction transfer after bariatric surgery. Other common behavioral changes that impact adherence, weight loss, and psychiatric risk after surgery are also reviewed. Last, recommendations for presurgical psychological evaluation and postoperative support are provided.

Predictors of weight loss in participants with obesity following bariatric surgery - A prospective longitudinal fMRI study

Prevalence rates of overweight and obesity are increasing worldwide and are amongst the leading causes of death. Participants with obesity also suffer from poorer mental health with a concomitant reduced quality of life. Bariatric surgery outperforms other existing weight optimization approaches. However, hitherto, it was not possible to identify factors predicting weight loss following surgery. Therefore, we aimed at investigating neural and behavioral predictors of weight loss, as well as the neurological underpinnings of food cue-induced craving before and after bariatric surgery. The total sample consisted of 26 participants with obesity (17 females and 9 males, mean age 41 ± 12 years, mean BMI 46 ± 6 kg/m2, 21 received Roux-en-Y gastric bypass and 5 sleeve gastrectomy). Participants with obesity were prospectively assessed using functional magnetic resonance imaging two weeks before, as well as eight and 24 weeks after surgery. Imaging data were available for 11 individuals; 10 received Roux-en-Y gastric bypass and one sleeve gastrectomy. Subjective cue-induced food craving correlated positively with brain activation in the amygdala, the parahippocampal gyrus, and hippocampus, and negatively with brain activation in frontal brain regions. In the total sample (N = 26), perceived feeling of hunger and YFAS sum score explained 50.6% of the variance (R² = 0.506, F_(1,23) = 10.759, p < 0.001) and in the imaging sample, cue-induced food craving at baseline before surgery explained 49.6% of the variance (R² = 0.496, F_(1,23) = 7.862, p = 0.023) of % total weight loss (%TWL). In other words, with respect to %TWL, bariatric surgery was most efficient in candidates characterized by high cue-induced food craving, high-perceived feeling of hunger and a low YFAS sum score.

Reward-related gustatory and psychometric predictors of weight loss following bariatric surgery: a multicenter cohort study

BACKGROUND

Reward sensitivity has been proposed as a potential mediator of outcomes for bariatric surgery.

OBJECTIVES

We aimed to determine whether gustatory and psychometric measures of reward-related feeding are predictors of bariatric-induced weight loss.

METHODS

A multicenter longitudinal cohort study was conducted in patients scheduled for bariatric surgery (surgical group), assessed at baseline and 2 follow-up assessments. Predictions of % weight loss from baseline (%WL) according to baseline gustatory measures, including intensity and pleasantness ratings of sweet and other tastants, and psychometric measures of reward-related feeding behavior, including hedonic hunger scores, were assessed with multivariable linear regression. Exploratory analyses were conducted to test for associations between %WL and changes in gustatory and psychophysical measures, as well as for comparisons with data from patients on the surgery waiting list (control group).

RESULTS

We included 212 patients, of whom 96 in the surgical group and 50 in the control group were prospectively assessed. The groups were similar at baseline and, as expected, bariatric surgery resulted in higher %WL (BTreatment-Time  = 2.4; 95% CI: 2.1-2.8; P  < 0.0001). While variation in gustatory measures did not differ between groups, in the surgery group baseline sweet intensity predicted %WL at the primary endpoint (11 to 18 months postoperatively; β = 0.2; B = 0.2, 95% CI: 0.02 to 0.3; P  = 0.02), as did hedonic hunger scores (β = -0.2; B = -2.0, 95% CI: -3.8 to -0.3; P  = 0.02). Furthermore, at this endpoint, postsurgical reduction of sweet taste intensity and acceptance of sweet foods were associated with %WL (β = -0.3; B = -3.5, 95% CI: -5.8 to -1.3; P  = 0.003, and β = -0.2; B = -4.7, 95% CI: -8.5 to -0.8; P  = 0.02, respectively). The use of sweet intensity as a predictor of weight change was confirmed in another bariatric cohort.

CONCLUSIONS

Sweet intensity ratings and hedonic hunger scores predict %WL after surgery. The variability of sweet intensity ratings is also associated with %WL, further suggesting they may reflect physiological processes that are variably modulated by bariatric surgery, influencing clinical outcomes.

Bariatric Surgical Alterations in Tolerability, Enjoyment and Cravings in the Diet (BSATED) instrument: A new scale to measure food preferences following bariatric surgery

Bariatric surgery is associated with changing food preferences, but it is not known whether these changes differ by type of operation or are associated with weight loss. The current study presents validation results for a new 27-item scale, Bariatric Surgical Alterations in Tolerability, Enjoyment and Cravings in the Diet (BSATED). This scale measured enjoyment, craving, and intolerance changes for nine food and beverage categories common to dietary habits in the Southern California region of the U.S. one year following bariatric surgery in the Bariatric Experience Long Term (BELONG) study. Validation of BSATED was done using exploratory factor analyses, construct validity with other conceptually related survey instruments, and criterion validity using hypothesized differences for operation type and percent total weight loss (%TWL) at 12-18 months after surgery. Participants (n = 999) were 86% female, 41% non-Hispanic White, with a mean age of 43.1 ± 11.3 years and a body mass index (BMI) of 43.4 ± 6.8 kg/m² at the time of surgery. Participants reported less enjoyment and craving for high-fat meats (62%), grains (54%), candy and other desserts (e.g. candy bars, chocolate, ice cream) (52%), and sweet baked goods (48%) 12 months after surgery. These changes were more common among participants undergoing Roux-en-Y gastric bypass (RYGB) compared to those receiving sleeve gastrectomy (SG). Participants who reported decreased enjoyment and craving for foods and beverages that post-bariatric patients are counseled to reduce or avoid had greater %TWL at 12-18 months following surgery (p < .001 and p = .003 respectively). The foods and beverages in BSATED that post-bariatric patients are counseled to reduce or avoid could be used to understand how changes in enjoyment, craving and tolerability of these foods/beverages contribute to weight loss following surgery.

Sleeve gastrectomy in patients with severe obesity restores circadian rhythms and their relationship with sleep pattern

Advances in research have linked alterations of circadian rhythms with obesity. However, few studies have focused on the recovery of the circadian expression after a weight loss treatment. Our aim was to study the alterations of the circadian rhythmicity due to morbid obesity and the recovery of the circadian pattern after weight loss in a cohort of patients who underwent sleeve gastrectomy. For this purpose, 41 patients with severe obesity (75% women; age [mean (SD)] 49.7 ± 10 years; BMI 44.3 ± 6.2 kg/m2) were monitored before bariatric surgery and 9 months afterward. On both occasions, activity and wrist temperature were determined by actigraphy and were related with weight loss. Anthropometric, biochemical, and sleep-related variables, along with dietary intake and physical activity, were analyzed in relation with circadian rhythmicity. Results show significant differences in the circadian expression before and after 9 months of bariatric surgery, with more stable and less fragmented rhythms after weight loss. Moreover, only after surgery were the circadian variables associated to sleep timing and chronotype. The findings of this study indicate that weight loss treatment in patients with morbid obesity improves the circadian rhythm expression, and in such a way that it could be associated with better sleep quality. Moreover, it allows the recovery of the relationship between sleep patterns and circadian rhythm that was lost due to the obesity.

Reliability of neural food cue-reactivity in participants with obesity undergoing bariatric surgery: a 26-week longitudinal fMRI study

Obesity is highly prevalent worldwide and results in a high disease burden. The efforts to monitor and predict treatment outcome in participants with obesity using functional magnetic resonance imaging (fMRI) depends on the reliability of the investigated task-fMRI brain activation. To date, no study has investigated whole-brain reliability of neural food cue-reactivity. To close this gap, we analyzed the longitudinal reliability of an established food cue-reactivity task. Longitudinal reliability of neural food-cue-induced brain activation and subjective food craving ratings over three fMRI sessions (T0: 2 weeks before surgery, T1: 8 weeks and T2: 24 weeks after surgery) were investigated in N = 11 participants with obesity. We computed an array of established reliability estimates, including the intraclass correlation (ICC), the Dice and Jaccard coefficients and similarity of brain activation maps. The data indicated good reliability (ICC > 0.6) of subjective food craving ratings over 26 weeks and excellent reliability (ICC > 0.75) of brain activation signals for the contrast of interest (food > neutral) in the caudate, putamen, thalamus, middle cingulum, inferior, middle and superior occipital gyri, and middle and superior temporal gyri and cunei. Using similarity estimates, it was possible to re-identify individuals based on their neural activation maps (73%) with a fading degree of accuracy, when comparing fMRI sessions further apart. The results show excellent reliability of task-fMRI neural brain activation in several brain regions. Current data suggest that fMRI-based measures might indeed be suitable to monitor and predict treatment outcome in participants with obesity undergoing bariatric surgery.

Brain Activity Associated With Regulating Food Cravings Predicts Changes in Self-Reported Food Craving and Consumption Over Time

Neural patterns associated with viewing energy-dense foods can predict changes in eating-related outcomes. However, most research on this topic is limited to one follow-up time point, and single outcome measures. The present study seeks to add to that literature by employing a more refined assessment of food craving and consumption outcomes along with a more detailed neurobiological model of behavior change over several time points. Here, a community sample of 88 individuals (age: M = 39.17, SD = 3.47; baseline BMI: M = 31.5, SD = 3.9, range 24–42) with higher body mass index (BMI) performed a food craving reactivity and regulation task while undergoing functional magnetic resonance imaging. At that time—and 1, 3, and 6 months later—participants reported craving for and consumption of healthy and unhealthy foods via the Food Craving Inventory (FCI) and ASA24 (N at 6 months = 52–55 depending on the measure). A priori hypotheses that brain activity associated with both viewing and regulating personally desired unhealthy, energy-dense foods would be associated with self-reported craving for and consumption of unhealthy foods at baseline were not supported by the data. Instead, regression models controlling for age, sex, and BMI demonstrated that brain activity across several regions measured while individuals were regulating their desires for unhealthy food was associated with the self-reported craving for and consumption of healthy food. The hypothesis that vmPFC activity would predict patterns of healthier eating was also not supported. Instead, linear mixed models controlling for baseline age and sex, as well as changes in BMI, revealed that more regulation-related activity in the dlPFC, dACC, IFG, and vmPFC at baseline predicted decreases in the craving for and consumption of healthy foods over the course of 6 months.

Baseline Presence of NAFLD Predicts Weight Loss after Gastric Bypass Surgery for Morbid Obesity

Background. Bariatric surgery is a widely used treatment for morbid obesity. Prediction of postoperative weight loss currently relies on prediction models, which mostly overestimate patients’ weight loss. Data about the influence of Non-alcoholic fatty liver disease (NAFLD) on early postoperative weight loss are scarce. Methods. This prospective, single-center cohort study included 143 patients receiving laparoscopic gastric bypass surgery (One Anastomosis-Mini Gastric Bypass (OAGB-MGB) or Roux-en-Y Gastric Bypass (RYGB)). Liver biopsies were acquired at surgery. NAFLD activity score (NAS) assigned patients to “No NAFLD”, “NAFL” or “NASH”. Follow up data were collected at 3, 6 and 12 months. Results. In total, 49.7% of patients had NASH, while 41.3% had NAFL. Compared with the No NAFLD group, NAFL and NASH showed higher body-mass-index (BMI) at follow-up (6 months: 31.0 kg/m² vs. 36.8 kg/m² and 36.1 kg/m², 12 months: 27.0 kg/m² vs. 34.4 and 32.8 kg/m²) and lower percentage of total body weight loss (%TBWL): (6 months: 27.1% vs. 23.3% and 24.4%; 12 months: 38.5% vs. 30.1 and 32.6%). Linear regression of NAS points significantly predicts percentage of excessive weight loss (%EWL) after 6 months (Cologne-weight-loss-prediction-score). Conclusions. Histopathological presence of NAFLD might lead to inferior postoperative weight reduction after gastric bypass surgery. The mechanisms underlying this observation should be further studied.

Brain Connectivity, and Hormonal and Behavioral Correlates of Sustained Weight Loss in Obese Patients after Laparoscopic Sleeve Gastrectomy

The biological mediators that support cognitive-control and long-term weight-loss after laparoscopic sleeve gastrectomy (LSG) remain unclear. We measured peripheral appetitive hormones and brain functional-connectivity (FC) using magnetic-resonance-imaging with food cue-reactivity task in 25 obese participants at pre, 1 month, and 6 month after LSG, and compared with 30 normal weight controls. We also used diffusion-tensor-imaging to explore whether LSG increases brain structural-connectivity (SC) of regions involved in food cue-reactivity. LSG significantly decreased BMI, craving for high-calorie food cues, ghrelin, insulin, and leptin levels, and increased self-reported cognitive-control of eating behavior. LSG increased FC between the right dorsolateral prefrontal cortex (DLPFC) and the pregenual anterior cingulate cortex (pgACC) and increased SC between DLPFC and ACC at 1 month and 6 month after LSG. Reduction in BMI correlated negatively with increased FC of right DLPFC-pgACC at 1 month and with increased SC of DLPFC-ACC at 1 month and 6 month after LSG. Reduction in craving for high-calorie food cues correlated negatively with increased FC of DLPFC-pgACC at 6 month after LSG. Additionally, SC of DLPFC-ACC mediated the relationship between lower ghrelin levels and greater cognitive control. These findings provide evidence that LSG improved functional and structural connectivity in prefrontal regions, which contribute to enhanced cognitive-control and sustained weight-loss following surgery.

Effect of Sleeve Gastrectomy on Ghrelin, GLP-1, PYY, and GIP Gut Hormones: A Systematic Review and Meta-analysis

OBJECTIVE

To perform a structured systematic review and meta-analysis to evaluate changes in ghrelin, glucagon-like peptide-1 (GLP-1), peptide YY (PYY), and gastric inhibitory peptide (GIP) gut hormone levels in patients after sleeve gastrectomy.

BACKGROUND

Despite sleeve gastrectomy becoming the most common surgical weight loss procedure, weight loss mechanisms remain less clear.

METHODS

Searches of PubMed, EMBASE, Web of Science, and Cochrane Library databases were performed through April 1, 2019, in accordance with PRISMA and MOOSE guidelines. Randomized controlled trials and prospective observational studies evaluating pre and post-procedure hormones fasting ghrelin, postprandial GLP-1, postprandial PYY, and fasting GIP levels were included. Hedge g with random-effects models were used to determine pooled effect size and corresponding 95% confidence intervals (CIs).

RESULTS

A total of 28 studies (n = 653; 29.56% male) were included. Mean age was 42.00 ± 5.48 years, with average follow-up of 11.70 ± 11.38 months. Pre-procedure body mass index (BMI) was 46.01 ± 4.07 kg/m with a postsleeve gastrectomy BMI of 34.07 ± 3.73 kg/m, representing total body weight loss of 25.13 ± 4.44% and excess weight loss of 57.48 ± 9.64% (P < 0.001). Ghrelin decreased (Hedge g -1.486, 95% CI -1.884 to -1.089, I = 91.95%), whereas GLP-1 and PYY increased post-procedure (Hedge g 1.095, 95% CI 0.509 to 1.642, I = 84.38%; and Hedge g 1.396, 95% CI 0.781 to 2.011, I = 84.02%, respectively). GIP did not significantly change (Hedge g -0.213, 95% CI -1.019 to 0.592, I = 79.65%).

CONCLUSIONS

Fasting ghrelin levels decreased, whereas postprandial GLP-1 and PYY increased after sleeve gastrectomy. Fasting GIP levels remained unchanged. Future studies are needed to assess the role of these gut hormones and relationship to weight loss and metabolic outcomes.

Emotional eating in patients attending a specialist obesity treatment service

OBJECTIVE

The prevalence of emotional eating (EE) has increased in the general population over past decades. There is limited information on how common EE is among people seeking obesity treatment. We aimed to estimate the proportion of people with EE, and strength of associations between a predefined set of factors and EE in people referred for obesity treatment.

METHODS

Cross-sectional study recruiting 387 adults from a hospital obesity service. "Emotional eating" was defined as Emotional Eating Scale (EES) score ≥25. Strength of associations were estimated by boot-strapped quantile regression analysis. Results are presented as quantile difference (QD) of EES scores at the 25th, 50th or 75th quantile, and 95% confidence intervals (95%CI).

RESULTS

The study population consisted of 71% women, with a median age of 52 years (interquartile range [IQR]: 42, 61), and a median body mass index of 42 kg/m² (IQR: 37, 49). 187 participants were managed with lifestyle modification alone, 103 with the addition of obesity pharmacotherapy, 79 with bariatric surgery, and 18 with both bariatric surgery and medications. EE was reported by an estimated 58% (95%CI: 53, 63) of participants. Factors with the largest and most consistent magnitude of association with EES differences include age, sex, use of glucagon-like peptide-1 (GLP-1) agonists, history of sleeve gastrectomy and recent bariatric surgery.

CONCLUSION

Emotional eating affected more than half of people referred for obesity treatment. Age, sex, use of GLP-1 agonists, history of sleeve gastrectomy and recent bariatric surgery had the strongest associations with EE. These findings allow hypothesis generation about the underlying physiological mechanisms behind emotional eating for investigation in future research.

Child neurobiology impacts success in family-based behavioral treatment for children with obesity

Background and Objectives:

Family-based behavioral treatment (FBT) is the recommended treatment for children with common obesity. However, there is a large variability in short- and long-term treatment response and mechanisms for unsuccessful treatment outcomes are not fully understood. In this study, we tested if brain response to visual food cues among children with obesity before treatment predicted weight or behavioral outcomes during a 6-mo. behavioral weight management program and/or long-term relative weight maintenance over a 1-year follow-up period.

Subjects and Methods:

Thirty-seven children with obesity (age 9–11y, 62% male) who entered active FBT (attended 2 or more sessions) and had outcome data. Brain activation was assessed at pre-treatment by functional magnetic resonance imaging across an a priori set of appetite-processing brain regions that included the ventral and dorsal striatum, medial orbitofrontal cortex, amygdala, substantia nigra/ventral tegmental area and insula in response to viewing food images before and after a standardized meal.

Results:

Children with more robust reductions in brain activation to high-calorie food cue images following a meal had greater declines in BMI z-score during FBT (r= 0.42; 95% CI: 0.09, 0.66; P=0.02) and greater improvements in Healthy Eating Index scores (r= −0.41; 95% CI: −0.67, −0.06; P=0.02). In whole-brain analyses, greater activation in the ventromedial prefrontal cortex, specifically by high-calorie food cues, was predictive of better treatment outcomes (whole-brain cluster corrected P=0.02). There were no significant predictors of relative weight maintenance and initial behavioral or hormonal measures did not predict FBT outcomes.

Conclusions:

Children’s brain responses to a meal prior to obesity treatment were related to treatment-based weight outcomes, suggesting that neurophysiologic factors and appetitive drive, more so than initial hormone status or behavioral characteristics, limit intervention success.

Change in emotional eating after bariatric surgery: systematic review and meta-analysis

BACKGROUND

The effect of bariatric surgery on 'emotional eating' (EE) in people with obesity is unclear. This systematic review and meta-analysis aimed to examine changes in self-reported emotional eating behaviour after bariatric surgery.

METHODS

Fifteen electronic databases were searched from inception to August 2019. Included studies encompassed patients undergoing primary bariatric surgery, quantitatively assessed EE, and reported EE scores before and after surgery in the same participants. Studies were excluded if they were not in English or available in full text. The systematic review and meta-analysis were conducted according to the PRISMA guidelines. Random-effects models were used for quantitative analysis. Study quality was assessed using the National Heart, Lung, and Blood Institute quality assessment tool for before-after (pre-post) studies with no control group.

RESULTS

Some 23 studies containing 6749 participants were included in the qualitative synthesis, with follow-up of from 2 weeks to 48 months. EE scores decreased to 12 months after surgery. Results were mixed beyond 12 months. Quantitative synthesis of 17 studies (2811 participants) found that EE scores decreased by a standardized mean difference of 1·09 (95 per cent c.i. 0·76 to 1·42) 4-18 months after surgery, indicating a large effect size.

CONCLUSION

Bariatric surgery may mitigate the tendency to eat in response to emotions in the short to medium term.

Recent Advances in the Neurobiology of Altered Motivation Following Bariatric Surgery

PURPOSE OF REVIEW

There is compelling evidence in the clinical population that long-term weight loss secondary to bariatric surgery is mitigated by the reemergence of maladaptive feeding behaviors and in some cases new onset substance abuse.

RECENT FINDINGS

A review of the current literature suggests that physical restructuring of the GI tract during WLS alters secretion of feeding peptides and nutrient-sensing mechanisms that directly target the brain's endogenous reward system, the mesolimbic dopamine system. Post-surgical changes in GI physiology augment activation of the mesolimbic system. In some patients, this process may contribute to a reduced appetite for palatable food whereas in others it may support maladaptive motivated behavior for food and chemical drugs. It is concluded that future studies are required to detail the timing and duration of surgical-induced changes in GI-mesolimbic communication to more fully understand this phenomenon.

Resting-State Brain Connectivity Predicts Weight Loss and Cognitive Control of Eating Behavior After Vertical Sleeve Gastrectomy

OBJECTIVE

The effects of sleeve gastrectomy (SG) on functional connectivity (FC) and associations with weight loss and eating-related cognitive control were investigated.

METHODS

In a longitudinal study, 14 SG patients (13 female; 42.1 presurgery BMI) completed study visits 1 month pre surgery and 12 months post surgery. Patients completed the Dutch Eating Behavior Questionnaire and resting-state functional magnetic resonance imaging scanning to measure FC. Data were analyzed using a seed-to-voxel approach in the CONN Toolbox to investigate pre-/postsurgery changes (n = 12) and to conduct predictive analysis (n = 14).

RESULTS

Seed-to-voxel analysis revealed changes in magnitude (decreases) and directionality (positively correlated to anticorrelated) of FC pre to post surgery within and between default mode network, salience network, and frontoparietal network nodes [Family-Wise Error (FWE) corrected at P < 0.05]. Baseline FC of the nucleus accumbens (with insula) and hypothalamus (with precentral gyrus) predicted 12-month post-SG % total weight loss (FWE-P < 0.05). Baseline FC of the hippocampus, frontoparietal network, and default mode network nodes predicted improvement in cognitive control of eating behavior 12 months after SG (FWE-P < 0.05).

CONCLUSIONS

Our findings demonstrate changes in FC magnitude and directionality post versus pre surgery within and between resting-state networks and frontal, paralimbic, and visual areas in SG patients. Baseline FC predicted weight loss and changes in cognitive control of food intake behavior at 12 months. These could serve as predictive biomarkers for bariatric surgery.

Uncontrolled eating: a unifying heritable trait linked with obesity, overeating, personality and the brain

Many eating-related psychological constructs have been proposed to explain obesity and overeating. However, these constructs, including food addiction, disinhibition, hedonic hunger, emotional eating, binge eating and the like all have similar definitions, emphasizing loss of control over intake. As questionnaires measuring the constructs correlate strongly (r > 0.5) with each other, we propose that these constructs should be reconsidered to be part of a single broad phenotype: uncontrolled eating. Such an approach enables reviewing and meta-analysing evidence obtained with each individual questionnaire. Here, we describe robust associations between uncontrolled eating, body mass index (BMI), food intake, personality traits and brain systems. Reviewing cross-sectional and longitudinal data, we show that uncontrolled eating is phenotypically and genetically intertwined with BMI and food intake. We also review evidence on how three psychological constructs are linked with uncontrolled eating: lower cognitive control, higher negative affect and a curvilinear association with reward sensitivity. Uncontrolled eating mediates all three constructs' associations with BMI and food intake. Finally, we review and meta-analyse brain systems possibly subserving uncontrolled eating: namely, (i) the dopamine mesolimbic circuit associated with reward sensitivity, (ii) frontal cognitive networks sustaining dietary self-control and (iii) the hypothalamus-pituitary-adrenal axis, amygdala and hippocampus supporting stress reactivity. While there are limits to the explanatory and predictive power of the uncontrolled eating phenotype, we conclude that treating different eating-related constructs as a single concept, uncontrolled eating, enables drawing robust conclusions on the relationship between food intake and BMI, psychological variables and brain structure and function.

Calorie information and dieting status modulate reward and control activation during the evaluation of food images

Several public health departments throughout North America have responded to the obesity epidemic by mandating that restaurants publish calories at the point of purchase-with the intention of encouraging healthier food decisions. To help determine whether accompanying calorie information successfully changes a food's appetitive value, this study investigated the influence of calorie information on brain responses to food images. During functional magnetic resonance imaging (fMRI) scanning, dieting (N = 22) and non-dieting (N = 20) participants viewed pictures of food with and without calorie information and rated their desire to eat the food. When food images were paired with calorie information, not only did self-reported desire to eat the food decrease, but reward system activation (Neurosynth-defined from the term "food") decreased and control system activation (the fronto-parietal [FP] control system) increased. Additionally, a parametric modulation of reward activation by food preferences was attenuated in the context of calorie information. Finally, whole brain multivariate pattern analysis (MVPA) revealed patterns of activation in a region of the reward system-the orbitofrontal cortex (OFC)-that were more similar for food images presented with and without calorie information in dieting than non-dieting participants, suggesting that dieters may spontaneously consider calorie information when viewing food. Taken together, these results suggest that calorie information may alter brain responses to food cues by simultaneously reducing reward system activation and increasing control system activation. Moreover, individuals with greater experience or stronger motivations to consider calorie information (i.e., dieters) may more naturally do so, as evidenced by a greater degree of representational similarity between food images with and without calorie information. Combining an awareness of calories with the motivation to control them may more effectively elicit diet-related behavior change.