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

Fasting appetite-related gut hormone responses after weight loss induced by calorie restriction, exercise, or both in people with overweight or obesity: a meta-analysis

OBJECTIVES

Altered appetite-related gut hormone concentrations may reflect a physiological adaptation facilitating weight regain after weight loss. This review investigates hormonal changes after weight loss achieved through calorie restriction (CR), exercise (EX), or both combined (CREX).

METHODS

A systematic search of PubMed (MEDLINE), EMBASE, SPORTDiscus, Cochrane Library, Web of Science, and ClinicalTrials.gov was conducted to identify randomised controlled trials (RCTs) and non-RCTs reporting in a fasting state either pre- and post-intervention appetite-related hormone concentrations or the changes therein after weight loss. The hormones examined were ghrelin, peptide tyrosine tyrosine (PYY), glucagon-like peptide -1 (GLP-1), and cholecystokinin (CCK), in their total and/or active form. Standardised mean differences (SMD) were extracted as the effect size.

RESULTS

127 studies were identified: 19 RCTs, 108 non-RCTs, 1305 and 4725 participants, respectively. In response to weight loss induced by CR, EX or CREX, the meta-analysis revealed an increase in total ghrelin from both RCTs (SMD: 0.55, 95% CI: 0.07-1.04) and non-RCTs (SMD: 0.24, 95% CI: 0.14-0.35). A decrease in acylated ghrelin was identified for RCTs (SMD: -0.58, 95% CI: -1.09 to -0.06) but an increase was observed for non-RCTs (SMD: 0.15, 95% CI: 0.03 to 0.27). Findings also revealed a decrease in PYY (total PYY: SMD: -0.17, 95%CI: -0.28 to -0.06; PYY3-36: SMD: -0.17, 95%CI: -0.32 to -0.02) and active GLP-1 (SMD: -0.16, 95% CI: -0.28 to -0.05) from non-RCTs. Changes in hormones did not differ among the three interventions when controlling for weight loss. Meta-regression indicated that greater weight loss was associated with a greater increase in total ghrelin.

CONCLUSIONS

Weight loss induced by CR, EX, or CREX elicits an increase in total ghrelin, but varied responses in other appetite-related hormones. The extent of weight loss influences changes in appetite-related gut hormone concentrations.

Plasma concentration of gastrointestinal hormones and subjective appetite ratings after diet or bariatric surgery: 1-year results from the DISGAP study

OBJECTIVE

Long-term weight loss outcomes are contrasting between bariatric surgery and dietary restriction alone. This is the first study to investigate changes in gastrointestinal (GI) hormones involved in appetite regulation, and subjective appetite feelings, at 1-year follow-up, after initial weight loss induced by a very-low energy (VLED) alone (controls), or with bariatric surgery.

METHODS

Patients scheduled for Sleeve Gastrectomy (SG) (n = 19) or Roux-en-Y gastric Bypass (RYGB) (n = 19), and controls (n = 16) were recruited. All groups underwent 10 weeks of a VLED (initial phase), followed by a 9-month maintenance phase. Body weight/composition, plasma concentrations of ghrelin, glucagon-like peptide 1 (GLP-1), peptide YY (PYY), cholecystokinin (CCK), and appetite ratings were measured before and after a meal, at baseline, week 11(W11), and 1Y follow-up.

RESULTS

Participants who completed all three follow ups were included in the analysis. Initial changes in body weight/composition were comparable across groups. SG (n = 11) and RYGB (n = 12) continued to lose weight from W11 to 1Y, whereas controls (n = 12) had regained weight. Postprandial GLP-1 increased over time post bariatric surgery and remained unchanged and lower in controls. Postprandial PYY increased in all groups, but greatest post-RYGB. Basal ghrelin decreased over time post-SG, while a small or marked increase was seen after RYGB and diet, respectively, with the control group exhibiting the greatest basal and postprandial concentrations at 1Y. A reduction in basal and postprandial CCK was seen in controls at 1Y, while no changes were observed post-bariatric surgery. Overall, small changes in subjective appetite ratings were seen over time.

CONCLUSION

Weight change at 1Y follow up after SG and RYGB is followed by a GI hormone profile favoring a lower drive to eat and increased satiety. The opposite is seen 1Y after WL induced by dietary restriction alone.

CLINICAL TRIAL REGISTRATION

clinicaltrials.gov NCT04051190.

Short-term effects of obesity surgery versus low-energy diet on body composition and tissue-specific glucose uptake: a randomised clinical study using whole-body integrated 18F-FDG-PET/MRI

AIMS/HYPOTHESIS

Obesity surgery (OS) and diet-induced weight loss rapidly improve insulin resistance. We aim to investigate the impact of either Roux-en-Y gastric bypass (RYGB) or sleeve gastrectomy (SG) surgery compared with a diet low in energy (low-calorie diet; LCD) on body composition, glucose control and insulin sensitivity, assessed both at the global and tissue-specific level in individuals with obesity but not diabetes.

METHODS

In this parallel group randomised controlled trial, patients on a waiting list for OS were randomised (no blinding, sealed envelopes) to either undergo surgery directly or undergo an LCD before surgery. At baseline and 4 weeks after surgery (n=15, 11 RYGB and 4 SG) or 4 weeks after the start of LCD (n=9), investigations were carried out, including an OGTT and hyperinsulinaemic-euglycaemic clamps during which concomitant simultaneous whole-body [18F]fluorodeoxyglucose-positron emission tomography (PET)/MRI was performed. The primary outcome was HOMA-IR change.

RESULTS

One month after bariatric surgery and initiation of LCD, both treatments induced similar reductions in body weight (mean ± SD: -7.7±1.4 kg and -7.4±2.2 kg, respectively), adipose tissue volume (7%) and liver fat content (2% units). HOMA-IR, a main endpoint, was significantly reduced following OS (-26.3% [95% CI -49.5, -3.0], p=0.009) and non-significantly following LCD (-20.9% [95% CI -58.2, 16.5). For both groups, there were similar reductions in triglycerides and LDL-cholesterol. Fasting plasma glucose and insulin were also significantly reduced only following OS. There was an increase in glucose AUC in response to an OGTT in the OS group (by 20%) but not in the LCD group. During hyperinsulinaemia, only the OS group showed a significantly increased PET-derived glucose uptake rate in skeletal muscle but a reduced uptake in the heart and abdominal adipose tissue. Both liver and brain glucose uptake rates were unchanged after surgery or LCD. Whole-body glucose disposal and endogenous glucose production were not significantly affected.

CONCLUSIONS/INTERPRETATION

The short-term metabolic effects seen 4 weeks after OS are not explained by loss of body fat alone. Thus OS, but not LCD, led to reductions in fasting plasma glucose and insulin resistance as well as to distinct changes in insulin-stimulated glucose fluxes to different tissues. Such effects may contribute to the prevention or reversal of type 2 diabetes following OS. Moreover, the full effects on whole-body insulin resistance and plasma glucose require a longer time than 4 weeks.

TRIAL REGISTRATION

ClinicalTrials.gov NCT02988011 FUNDING: This work was supported by AstraZeneca R&D, the Swedish Diabetes Foundation, the European Union's Horizon Europe Research project PAS GRAS, the European Commission via the Marie Sklodowska Curie Innovative Training Network TREATMENT, EXODIAB, the Family Ernfors Foundation, the P.O. Zetterling Foundation, Novo Nordisk Foundation, the Agnes and Mac Rudberg Foundation and the Uppsala University Hospital ALF grants.

Gut peptides before and following Roux-En-Y gastric bypass: A systematic review and meta-analysis

A systematic search was conducted in Medline Ovid, Embase, Scopus, and Cochrane Central Register of Controlled Trials up until March 2021 following PRISMA guidelines. Studies included evaluated ghrelin, GLP-1, PYY or appetite sensation via visual analogue scales (VASs) before and after Roux-en-Y gastric bypass (RYGB) in adults. A multilevel model with random effects for study and follow-up time points nested in study was fit to the data. The model included kcal consumption as a covariate and time points as moderators. Among the 2559 articles identified, k = 47 were included, among which k = 19 evaluated ghrelin, k = 40 GLP-1, k = 22 PYY, and k = 8 appetite sensation. Our results indicate that fasting ghrelin levels are decreased 2 weeks post-RYGB (p = 0.005) but do not differ from baseline from 6 weeks to 1-year post-RYGB. Postprandial ghrelin and fasting GLP-1 levels were not different from pre-surgical values. Postprandial levels of GLP-1 increased significantly from 1 week (p < 0.001) to 2 years post-RYGB (p < 0.01) compared with pre-RYGB. Fasting PYY increased at 6 months (p = 0.034) and 1 year (p = 0.029) post-surgery; also, postprandial levels increased up to 1 year (p < 0.01). Insufficient data on appetite sensation were available to be meta-analyzed.

Suboptimal Weight Loss 13 Years After Roux-en-Y Gastric Bypass Is Associated with Blunted Appetite Response

PURPOSE

Bariatric surgery remains the most efficient treatment to achieve a sustained weight loss. However, a large proportion of patients experience suboptimal weight loss (SWL). The exact mechanisms involved remain to be fully elucidated, but the homeostatic appetite control system seems to be involved. The aim of this study was, therefore, to compare the plasma concentration of gastrointestinal hormones, and appetite ratings, between those experiencing SWL and optimal weight loss (OWL) after Roux-en-Y gastric bypass (RYGB).

MATERIALS AND METHODS

Fifty participants from the Bariatric Surgery Observation Study (BAROBS) experiencing either SWL or OWL (< or ≥ 50% of excess weight loss (EWL), respectively) > 13 years post-RYGB were compared to 25 non-surgical controls. Plasma concentrations of acylated ghrelin (AG), total glucagon-like peptide-1 (GLP-1), total peptide YY (PYY), cholecystokinin (CCK), and subjective ratings of hunger, fullness, desire to eat (DTE), and prospective food consumption (PFC) were assessed in the fasting and postprandial (area under the curve (AUC)) states.

RESULTS

Those experiencing OWL presented with higher basal AG and GLP-1 iAUC, and lower AG iAUC compared with SWL and controls. Additionally, both bariatric groups presented with higher PYY and CCK iAUC compared to controls. PFC tAUC was also lower in OWL compared to the SWL group. Total weight loss was positively correlated with GLP-1 tAUC and negatively correlated with fasting and tAUC DTE and PFC tAUC.

CONCLUSIONS

SWL > 13 years post-RYGB is associated with lower basal ghrelin, as well as a weaker satiety response to a meal. Future studies should investigate the causality of these associations.

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.

Effects of bariatric surgery and dietary interventions for obesity on brain neurotransmitter systems and metabolism: A systematic review of positron emission tomography (PET) and single-photon emission computed tomography (SPECT) studies

This systematic review collates studies of dietary or bariatric surgery interventions for obesity using positron emission tomography and single-photon emission computed tomography. Of 604 publications identified, 22 met inclusion criteria. Twelve studies assessed bariatric surgery (seven gastric bypass, five gastric bypass/sleeve gastrectomy), and ten dietary interventions (six low-calorie diet, three very low-calorie diet, one prolonged fasting). Thirteen studies examined neurotransmitter systems (six used tracers for dopamine DRD2/3 receptors: two each for 11 C-raclopride, 18 F-fallypride, 123 I-IBZM; one for dopamine transporter, 123 I-FP-CIT; one used tracer for serotonin 5-HT2A receptor, 18 F-altanserin; two used tracers for serotonin transporter, 11 C-DASB or 123 I-FP-CIT; two used tracer for μ-opioid receptor, 11 C-carfentanil; one used tracer for noradrenaline transporter, 11 C-MRB); seven studies assessed glucose uptake using 18 F-fluorodeoxyglucose; four studies assessed regional cerebral blood flow using 15 O-H2 O (one study also used arterial spin labeling); and two studies measured fatty acid uptake using 18 F-FTHA and one using 11 C-palmitate. The review summarizes findings and correlations with clinical outcomes, eating behavior, and mechanistic mediators. The small number of studies using each tracer and intervention, lack of dietary intervention control groups in any surgical studies, heterogeneity in time since intervention and degree of weight loss, and small sample sizes hindered the drawing of robust conclusions across studies.

No Evidence That Circulating GLP-1 or PYY Are Associated with Increased Satiety during Low Energy Diet-Induced Weight Loss: Modelling Biomarkers of Appetite

Bariatric surgery and pharmacology treatments increase circulating glucagon-like peptide-1 (GLP-1) and peptide YY (PYY), in turn promoting satiety and body weight (BW) loss. However, the utility of GLP-1 and PYY in predicting appetite response during dietary interventions remains unsubstantiated. This study investigated whether the decrease in hunger observed following low energy diet (LED)-induced weight loss was associated with increased circulating 'satiety peptides', and/or associated changes in glucose, glucoregulatory peptides or amino acids (AAs). In total, 121 women with obesity underwent an 8-week LED intervention, of which 32 completed an appetite assessment via a preload challenge at both Week 0 and Week 8, and are reported here. Visual analogue scales (VAS) were administered to assess appetite-related responses, and blood samples were collected over 210 min post-preload. The area under the curve (AUC_0-210), incremental AUC (iAUC_0-210), and change from Week 0 to Week 8 (∆) were calculated. Multiple linear regression was used to test the association between VAS-appetite responses and blood biomarkers. Mean (±SEM) BW loss was 8.4 ± 0.5 kg (-8%). Unexpectedly, the decrease in ∆AUC_0-210 hunger was best associated with decreased ∆AUC_0-210 GLP-1, GIP, and valine (p < 0.05, all), and increased ∆AUC_0-210 glycine and proline (p < 0.05, both). The majority of associations remained significant after adjusting for BW and fat-free mass loss. There was no evidence that changes in circulating GLP-1 or PYY were predictive of changes in appetite-related responses. The modelling suggested that other putative blood biomarkers of appetite, such as AAs, should be further investigated in future larger longitudinal dietary studies.

Endoscopic sleeve gastroplasty: early results of a minimally invasive procedure in patients with obesity

OBJECTIVES

We aimed to analyze the efficacy and safety of endoscopic sleeve gastroplasty at 3 months as well as to determine factors influencing post-procedural weight loss.

METHODS

Seventy-three patients with obesity classes I, II and III (BMI 31.1-46.6 kg/m²) underwent ESG between September 2021 and April 2022 at a tertiary care hospital using Overstitch (Apollo Endosurgery, Austin, TX). ESG's efficacy and safety was evaluated at 1 and 3 months post-procedure with regard to excess weight loss (EWL) and total weight loss (TWL). Categorical variables were expressed as percentages and compared with chi-square test while continuous variables were expressed as mean ± standard deviation and compared with paired t test and analysis of variance (ANOVA) as applicable. Pearson's correlation was used to determine association between factors at baseline and weight loss.

RESULTS

Mean age was 49.2 ± 9.7 years with 61 (83.6%) patients being female. Mean initial weight was 105.7 ± 15.7 kg, and mean BMI was 38.6 ± 3.5 kg/m². Median hospitalization was 2.0 ± 1.8 days with 62 (84.9%) patients discharged after 24 h. One patient had accidental suturing of the stomach to the abdominal wall and diaphragm which was managed laparoscopically. Mean %EWL was 25.4 ± 7.1 and 36.3 ± 11.4, and %TBWL was 11.2 ± 2.6 and 15.8 ± 4.2 at 1 and 3 months, respectively. Significant excess weight loss at 3 months was only observed in patients with BMI < 40 kg/m² (p = 0.001).

CONCLUSIONS

ESG is safe and effective to manage obesity. Significant weight loss at 3 months was only observed in patients with obesity class I and class II.

Gastrointestinal hormones and appetite ratings after weight loss induced by diet or bariatric surgery

OBJECTIVE

The aim of this study was to compare changes in gastrointestinal hormones and appetite ratings after a similar weight loss induced by a very low-energy diet alone or in combination with sleeve gastrectomy (SG) or Roux-en-Y gastric bypass (RYGB).

METHODS

Patients with severe obesity scheduled for SG (n = 15) and RYGB (n = 14) and 15 controls (very low-energy diet alone) were recruited. Body weight/composition, plasma concentrations of ß-hydroxybutyric acid, acylated ghrelin, total glucagon-like peptide-1, total peptide YY, cholecystokinin, and ratings of hunger, fullness, desire to eat, and prospective food consumption were measured pre- and postprandially, before and after 10 weeks of intervention.

RESULTS

Changes in body weight/composition and level of ketosis were similar across groups. In SG and RYGB, basal and postprandial acylated ghrelin declined, and postprandial glucagon-like peptide-1 increased, both significantly more compared with controls. Postprandial peptide YY increased in all groups. Overall, postprandial hunger decreased, and postprandial fullness increased. But ratings of desire to eat and prospective food consumption were more favorable after both surgeries compared with controls.

CONCLUSIONS

Weight loss with SG and RYGB leads to more favorable changes in gastrointestinal hormones compared with diet alone, although ratings of appetite were reduced across all groups.

Obesity and bariatric surgery in adults living with severe mental illness: perceptions and clinical challenges

Overweight and obesity are twice as likely to develop in people living with severe mental illness (SMI), compared with those without. Many factors contribute to this, such as reduced physical activity and the use of certain medications that induce weight gain. Obesity contributes to the premature mortality seen in people living with SMI, as it is one of the fundamental risk factors for cardiovascular disease and diabetes. Bariatric surgery is an effective treatment option, although patients living with SMI might face stigma when being considered for surgical intervention. This article proposes a discussion around obesity and bariatric surgery in patients living with SMI. It will also reflect on the challenges faced by healthcare professionals and patients living with SMI and obesity, when considering appropriate treatments for weight loss. The paper utilises a fictional case, informed by contributions from a lived experience author, to explore bariatric surgery in people living with SMI.

Associations of physical activity and sedentary behavior with appetite sensations and eating regulation behaviors before and during the initial year following bariatric surgery

Background

Bariatric surgery produces weight loss in part by impacting appetite and eating behavior. Research suggests physical activity (PA) assists with regulation of appetite and eating during non-surgical weight loss, although whether PA carries similar benefits in the context of bariatric surgery is unknown.

Objective

Evaluate associations of moderate-to-vigorous intensity PA (MVPA) and sedentary time (ST) with appetite sensations (hunger [homeostatic/hedonic], satiety) and eating regulation behaviors (restraint, disinhibition) before and during the initial year following bariatric surgery.

Method

Adult bariatric patients received an accelerometer to measure MVPA/ST and a smartphone to complete appetite/eating ratings at four semi-random times daily for 10 days at pre- and 3-, 6-, and 12-months post-surgery. Data were analyzed using generalized linear mixed models.

Results

Higher MVPA levels related to more satiety across time (p = 0.045) and more restraint at 3-months post-surgery (p < 0.001). At pre-surgery, higher MVPA levels also related to more disinhibition (p's < 0.01), although participants reported more disinhibition on days they performed less MVPA than usual (p = 0.017). MVPA did not relate to hunger. Lower ST levels related to more hedonic hunger (p = 0.003), especially at 12-months post-surgery (p < 0.001), and participants reported more homeostatic hunger on days they accumulated more ST than usual (p = 0.044). Additionally, higher ST levels related to more disinhibition at 3-months post-surgery (p's < 0.01) and lower restraint at pre-surgery (p's < 0.05). ST did not relate to satiety.

Conclusions

This study is the first to show that MVPA and ST each associate with appetite and eating regulation in daily life before and during post-surgical weight loss. Results, while preliminary and requiring experimental confirmation, highlight potential for targeting bariatric patients' activity behaviors to enhance modulation of appetite, control of food intake, and resistance to overeating.

Does a Higher Protein Diet Promote Satiety and Weight Loss Independent of Carbohydrate Content? An 8-Week Low-Energy Diet (LED) Intervention

Both higher protein (HP) and lower carbohydrate (LC) diets may promote satiety and enhance body weight (BW) loss. This study investigated whether HP can promote these outcomes independent of carbohydrate (CHO) content. 121 women with obesity (BW: 95.1 ± 13.0 kg, BMI: 35.4 ± 3.9 kg/m2) were randomised to either HP (1.2 g/kg BW) or normal protein (NP, 0.8 g/kg BW) diets, in combination with either LC (28 en%) or normal CHO (NC, 40 en%) diets. A low-energy diet partial diet replacement (LEDpdr) regime was used for 8 weeks, where participants consumed fixed-energy meal replacements plus one ad libitum meal daily. Four-day dietary records showed that daily energy intake (EI) was similar between groups (p = 0.744), but the difference in protein and CHO between groups was lower than expected. Following multiple imputation (completion rate 77%), decrease in mean BW, fat mass (FM) and fat-free mass (FFM) at Week 8 in all was 7.5 ± 0.7 kg (p < 0.001), 5.7 ± 0.5 kg (p < 0.001), and 1.4 ± 0.7 kg (p = 0.054) respectively, but with no significant difference between diet groups. LC (CHO×Week, p < 0.05), but not HP, significantly promoted postprandial satiety during a preload challenge. Improvements in blood biomarkers were unrelated to LEDpdr macronutrient composition. In conclusion, HP did not promote satiety and BW loss compared to NP LEDpdr, irrespective of CHO content.

Plasma Free Fatty Acid Concentration as a Modifiable Risk Factor for Metabolic Disease

Plasma free fatty acid (FFA) concentration is elevated in obesity, insulin resistance (IR), non-alcoholic fatty liver disease (NAFLD), type 2 diabetes (T2D), and related comorbidities such as cardiovascular disease (CVD). Furthermore, experimentally manipulating plasma FFA in the laboratory setting modulates metabolic markers of these disease processes. In this article, evidence is presented indicating that plasma FFA is a disease risk factor. Elevations of plasma FFA can promote ectopic lipid deposition, IR, as well as vascular and cardiac dysfunction. Typically, elevated plasma FFA results from accelerated adipose tissue lipolysis, caused by a high adipose tissue mass, adrenal hormones, or other physiological stressors. Reducing an individual’s postabsorptive and postprandial plasma FFA concentration is expected to improve health. Lifestyle change could provide a significant opportunity for plasma FFA reduction. Various factors can impact plasma FFA concentration, such as chronic restriction of dietary energy intake and weight loss, as well as exercise, sleep quality and quantity, and cigarette smoking. In this review, consideration is given to multiple factors which lead to plasma FFA elevation and subsequent disruption of metabolic health. From considering a variety of medical conditions and lifestyle factors, it becomes clear that plasma FFA concentration is a modifiable risk factor for metabolic disease.

Appetite control: hormones or diet strategies?

PURPOSE OF REVIEW

Appetite control results from metabolic, behavioral, and environmental factors that influence hunger and the desire to eat. We summarize the latest advances in the hormonal and nutritional strategies to control appetite and reduce hunger.

RECENT FINDINGS

The fed-hunger-state is regulated by central and peripheric hormones, which modulate energy balance. Leptin, insulin, ghrelin, peptide YY (PYY), and other gut-derived peptides represent the main appetite controllers. The role of orexins, obestatin, and liver-expressed antimicrobial peptide 2 has been uncovered recently. New insights have demonstrated the role of hippocampal activity as a possible mechanism of action. Glucagon-like peptide 1 (GLP1) receptor agonists are well known agents controlling appetite. Association of GLP1 receptor agonist, PYY, or glucose-dependent insulinotropic polypeptide agonists have been tested as new approaches. Appetite-control hormones have also risen as factors involved in the efficacy of bariatric procedures. High-protein, ketogenic diet, and intermittent fasting have been described as nutritional strategies to reduce appetite, although the physiological mechanism and long-term safety remains unclear.

SUMMARY

Appetite control has been an important target for the treatment of obesity and associated disorders. New studies have demonstrated promising adoption of dietary approaches, hormone-based drugs, and bariatric surgery to control energy intake. Further research will establish a significant association, benefits, and safety of these new therapies.

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

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