Patients lacking sustainable long-term weight loss after gastric bypass surgery show signs of decreased inhibitory control of prepotent responses

Distinct adaptations of endocrine and cognitive functions may contribute to high variability in long-term weight loss outcome after bariatric surgery

BACKGROUND

Bariatric surgery has been widely recognized as the most efficient long-term treatment method in severe obesity, yet therapy success shows considerable interindividual variability. Postoperative metabolic adaptations, including improved gut hormone secretion (GLP-1, PYY and ghrelin), and restored executive function may play an explanatory role in weight loss, yet causes for poor success in individual patients remain unknown. This study investigates gut-hormonal and cognitive characteristics in extreme weight loss responders to bariatric surgery.

METHODS

Patients (n=47) with high or low excessive weight loss (EWL) at least 2 years after Roux-en-Y-gastric bypass or sleeve gastrectomy were allocated into good responders (GR, EWL 82.4 ± 11.6%) and poor responders (PR, EWL 24.0 ± SD 12.8%) to study differences in postprandial secretion of GLP-1, PYY, ghrelin and in working memory (WM).

RESULTS

Mean BMI was 47.1 ± 6.2 kg/m² in PR (n=21) and 28.9 ± 3.1 kg/m² in GR (n=26, p < 0.001). Fasted GLP-1 and PYY were comparable for GR and PR (p > 0.2) and increased strongly after a standardized test meal (300 kcal liquid meal) with a peak at 15 to 30 minutes. The increase was stronger in GR compared to PR (GLP-1, PYY: Time x Group p < 0.05). Plasma ghrelin levels already differed between groups at fasted state, showing significantly higher levels for GR (p < 0.05). Postprandially, ghrelin secretion was suppressed in both groups, but suppression was higher in GR (Time x Group p < 0.05). GR showed significantly higher WM scores than PR (p < 0.05). Postprandial ghrelin (iAUC), but not GLP-1 or PYY plasma levels, significantly mediated the relationship between EWL and a WM subscore (IS score, CI = 0.07 - 1.68), but not WM main score (MIS score, CI = -0.07 - 1.54), in mediation analyses.

CONCLUSION

Excess weight loss success after bariatric surgical procedures is associated with distinct profiles of gut-hormones at fasted and postprandial state, and differences in working memory. Better working memory performance in GR might be mediated by higher postprandial reduction in ghrelin plasma levels. Future studies need to integrate longitudinal data, larger samples and more sensitive cognitive tests.

Measuring food-related inhibition with go/no-go tasks: Critical considerations for experimental design

The use of go/no-go tasks to assess inhibitory control over food stimuli is becoming increasingly popular. However, the wide variability in the design of these tasks makes it difficult to fully leverage their results. The goal of this commentary was to provide researchers with crucial aspects to consider when designing food-related go/no-go experiments. We examined 76 studies that used food-themed go/no-go tasks and extracted characteristics related to participant population, methodology, and analysis. Based on our observations of common issues that can influence study conclusions, we stress the importance for researchers to design an appropriate control condition and match stimuli between experimental conditions in terms of emotional and physical properties. We also emphasize that stimuli should be tailored to the participants under study, whether at the individual or group level. To ensure that the task truly measures inhibitory abilities, researchers should promote the establishment of a prepotent response pattern by presenting more go than no-go trials and by using short trials. Researchers should also pre-specify the criteria used to identify potentially invalid data. While go/no-go tasks represent valuable tools for studying food cognition, researchers should choose task parameters carefully and justify their methodological and analytical decisions in order to ensure the validity of results and promote best practices in food-related inhibition research.

The impact of impulsivity on weight loss after bariatric surgery: a systematic review

BACKGROUND

Impulsivity has been shown to be associated with obesity through links to pathological eating behavior such as binge eating. The recent literature suggests that impulsivity is linked to poorer outcomes post-bariatric surgery. Impulsivity can be measured in various ways and comprises of three broad domains: impulsive choice, impulsive action, and impulsive personality traits. The aim of this systematic review is to synthesize the current evidence on the impact of impulsivity on post-bariatric surgery weight loss.

METHODS

A literature review was performed in February 2020. Original studies investigating the relationship between impulsivity and weight loss post-bariatric surgery were evaluated.

RESULTS

Ten studies with a total of 1246 patients were analyzed. There were four case-control, four prospective observational and two retrospective observational studies. The postoperative follow-up ranged from 0.5 to 12 years. Eight studies measuring trait impulsivity did not show any association with weight loss post-bariatric surgery, although two studies reported an indirect effect of impulsivity on weight loss mediated via pathological eating behavior. Assessment of impulsive action by two studies showed that post-bariatric surgery weight loss is affected by impulsive action.

CONCLUSION

Impulsivity may adversely affect postoperative outcomes after bariatric surgery. However, this may be specific to state impulsivity or impulsive action rather than trait impulsivity. Patients with a higher state impulsivity may benefit from closer follow-up post-bariatric surgery, as well as cognitive behavioral therapies targeting cognitive control over food.

LEVEL OF EVIDENCE

Level I, systematic review.

Executive Functions in Predicting Weight Loss and Obesity Indicators: A Meta-Analysis

While previous studies have suggested that there exists a relationship between obesity and executive function (EF), the mechanisms and causal relationship between them remain unclear. There are important clinical implications of determining whether EF can predict and treat obesity. We conducted a multilevel meta-analysis of randomized controlled trials (RCTs) and longitudinal studies. Specifically, we investigate (a) whether EF interventions have an effect on weight loss, (b) whether baseline EF can be a predictor of future weight loss through obesity intervention, and (c) whether early-life EF can predict future weight loss. Eight RCTs and 17 longitudinal studies with a total of 11,393 participants were identified. We found that (a) EF interventions may not have an effect on weight loss, (b) baseline inhibition (β = 0.259, p = 0.03) and delay discounting (β = −0.17, p = 0.04) significantly predict future weight loss through obesity intervention, (c) age (F = 13.666, p = 0.005) moderates the relationship between working memory and weight loss through intervention, but not weight status, type of intervention, and percentage of female, and (d) early life inhibition (β = 0.185, p = 0.07) is a marginally significant predictor of future weight loss. Our results seem to support the assumption that the relationship between EF and obesity is not direct, and a higher-order factor, such as genes, may link obesity and EF. Building on the preliminary findings, further studies focusing on EF and obesity are needed in the future.

Executive function in individuals with clinically significant weight loss via behavioral intervention

BACKGROUND

Executive function (EF) is associated with obesity development and self-management. Individuals who demonstrate or self-report poorer EF performance tend to have poorer short-term outcomes in obesity treatment. There may be distinct behavioral self-management strategies and EF domains related to initial weight loss as compared to weight loss maintenance.

OBJECTIVE

To characterize EF in individuals who achieved clinically significant weight loss via behavioral intervention and examine potential differences in EF between those who maintained versus regained lost weight.

METHODS

Participants who previously achieved ≥5% weight loss via lifestyle intervention were included (N = 44). "Maintainers" (n = 16) maintained this minimum level of weight loss for ≥1 year. "Regainers" (n = 28) regained some or all initially lost weight. Performance-based EF, intelligence quotient, health literacy, depression, anxiety, binge eating, demographics, and medical/weight history were assessed using a cross-sectional design. Descriptive statistics and age-, gender-, education-adjusted reference ranges were used to characterize EF. Analyses of covariance were conducted to examine EF differences between maintainers and regainers.

RESULTS

The sample consisted primarily of females with obesity over age 50. Approximately half self-identified as African-American. Decision-making performance was better in maintainers than regainers (p = 0.003, partη2 = 0.19). There were no differences between maintainers and regainers in inhibitory control, verbal fluency, planning/organization, cognitive flexibility, or working memory (ps > 0.05, partη2s = 0.003-0.07). At least 75% of the sample demonstrated average-above average EF test performance, indicated by scaled scores ≥13 or t-scores > 60.

CONCLUSIONS

Most individuals with obesity who achieved clinically significant weight loss via behavioral intervention had average to above average EF. Individuals who maintained (vs. regained) their lost weight performed better on tests of decision-making.

Neurocognitive and Psychopathological Predictors of Weight Loss After Bariatric Surgery: A 4-Year Follow-Up Study

Twenty to thirty percent of patients experience weight regain at mid and long-term follow-up. Impaired cognitive functions are prevalent in people suffering from obesity and in those with binge eating disorder, thereby, affecting the weight-loss outcomes. The aim of our study was to investigate neurocognitive and psychopathological predictors of surgical efficacy in terms of percentage of excess weight loss (%EWL) at follow-up intervals of one year and 4-year. Psychosocial evaluation was completed in a sample of 78 bariatric surgery candidates and included psychometric instruments and a cognitive battery of neuropsychological tests. A schedule of 1-year and 4-year follow-ups was implemented. Wisconsin Sorting Card Test total correct responses, scores on the Raven's Progressive Matrices Test, and age predicted %EWL at, both, early and long-term periods after surgery while the severity of pre-operative binge eating (BED) symptoms were associated with lower %EWL only four years after the operation. Due to the role of pre-operative BED in weight loss maintenance, the affected patients are at risk of suboptimal response requiring ongoing clinical monitoring, and psychological and pharmacological interventions when needed. As a result of our findings and in keeping with the latest guidelines we encourage neuropsychological assessment of bariatric surgery candidates. This data substantiated the rationale of providing rehabilitative interventions tailored to cognitive domains and time specific to the goal of supporting patients in their post-surgical course.

The effects of bariatric surgery on psychological aspects of eating behaviour and food intake in humans

Bariatric surgery has emerged as an increasingly popular weight loss intervention, with larger and more endurable weight loss compared to pharmacological and behavioural interventions. The degree of weight loss patients experience varies, between individuals, surgeries and over time. An explanation as to why differing weight loss trajectories exist post-surgery could be due to the complex interplay of individual differences in relation to eating behaviours and appetite. Thus the aim of this narrative review is to explore literature between 2008 and 2018, to assess the impact of impact of bariatric surgery on food selection and nutrient status, on eating behaviour traits and on disturbed and disordered eating behaviour, to determine their impact of weight loss success and weight loss trajectories. Immediately post-surgery, up until 1-2 years post-surgery, there is a reliance upon the surgery's alteration of the gastrointestinal tract to control food intake and subsequently lose weight. Energy intake is reduced, dietary adherence is higher, supplement intake is higher, appetite ratings are lower, there is a reduction in psychopathology, and an increase in wellbeing. After this point, patients become more susceptible to weight regain, as this is the point where passive observation of the weight reducing action of surgery, moves into more cognitive effort, on the part of the individual, to control energy intake. There are various factors which influence an individual's ability to successfully regulate their energy intake post-surgery, such as their level of Disinhibition, Restraint, Hunger, Emotional Eating, Uncontrolled Eating, psychopathology and wellbeing. The need for continued psychological and nutritional support post-surgery is necessary to reduce weight regain susceptibility.

Bariatric Surgery Alters microRNA Content of Circulating Exosomes in Patients with Obesity

OBJECTIVE

Exosomal microRNAs (miRNAs) are potential biomarkers for obesity, in which they regulate biological processes. Bariatric surgery has health benefits for patients with obesity; however, the mechanisms of these benefits are not clear. This study attempted to identify the exosomal miRNA signature associated with obesity and how it changed after bariatric surgery.

METHODS

Healthy volunteers (HVs) and nondiabetic patients with obesity were prospectively enrolled in the study. The study assessed the serum exosomal miRNA profiles of HVs and patients with obesity using RNA sequencing. To evaluate the effects of bariatric surgery, the study also analyzed exosomal miRNAs in patients 6 months after surgery.

RESULTS

RNA sequencing revealed differential expression of 72 exosomal miRNAs in patients with obesity compared with HVs and differential expression of 41 miRNAs in post- versus presurgery blood. Among the differentially expressed miRNAs, the study identified nine surgery-responsive miRNAs that were highly expressed in patients before surgery compared with HVs. Biological pathway analysis of the nine miRNAs indicated that they are likely involved in WNT, neurotrophin, and insulin signaling; the insulin receptor signaling cascade; and focal adhesion.

CONCLUSIONS

Patients with obesity have a distinct exosomal miRNA expression profile compared with HVs. In addition, weight loss after surgery alters the exosomal miRNA profile of patients with obesity.

Higher resting-state activity in reward-related brain circuits in obese versus normal-weight females independent of food intake

BACKGROUND

In response to food cues, obese vs normal-weight individuals show greater activation in brain regions involved in the regulation of food intake under both fasted and sated conditions. Putative effects of obesity on task-independent low-frequency blood-oxygenation-level-dependent signals-that is, resting-state brain activity-in the context of food intake are, however, less well studied.

OBJECTIVE

To compare eyes closed, whole-brain low-frequency BOLD signals between severely obese and normal-weight females, as assessed by functional magnetic resonance imaging (fMRI).

METHODS

Fractional amplitude of low-frequency fluctuations were measured in the morning following an overnight fast in 17 obese (age: 39±11 years, body mass index (BMI): 42.3±4.8 kg m^-2) and 12 normal-weight females (age: 36±12 years, BMI: 22.7±1.8 kg m^-2), both before and 30 min after consumption of a standardized meal (~260 kcal).

RESULTS

Compared with normal-weight controls, obese females had increased low-frequency activity in clusters located in the putamen, claustrum and insula (P<0.05). This group difference was not altered by food intake. Self-reported hunger dropped and plasma glucose concentrations increased after food intake (P<0.05); however, these changes did not differ between the BMI groups.

CONCLUSION

Reward-related brain regions are more active under resting-state conditions in obese than in normal-weight females. This difference was independent of food intake under the experimental settings applied in the current study. Future studies involving males and females, as well as utilizing repeated post-prandial resting-state fMRI scans and various types of meals are needed to further investigate how food intake alters resting-state brain activity in obese humans.