Decreased Glucagon-like Peptide 1 Release after Weight Loss in Overweight/Obese Subjects

The Interplay Between Psychological and Neurobiological Predictors of Weight Regain: A Narrative Review

Introduction: Obesity is a global health problem requiring effective interventions to achieve weight loss and maintain it in the long term. A major challenge for clinicians is weight regain (WR), defined as progressive weight gain following successful weight loss. WR is affected by multiple factors, including psychological traits linked to specific brain alterations. Understanding these mechanisms is crucial in developing strategies to prevent WR and to ensure effective weight control. Objectives: This narrative review aims to gather current findings on the psychological and neurobiological determinants of WR and to discuss the interplay between these factors. Methods: A literature search was conducted on PubMed, Medline, and Web of Science for English-language studies published between December 1990 and November 2024. Results: WR is driven by interconnected psychological and neurobiological factors that influence eating behavior and the regulation of body weight. Certain personality traits and emotional patterns are associated with specific changes in brain activity, which together affect vulnerability to WR. Although distinct mechanisms can be identified, the complexity of homeostatic and nonhomeostatic appetite control suggests that no single factor predominates. Conclusions: This review highlights the dynamic interplay between psychological and neurobiological predictors of WR. However, due to the narrative nature of this review, the focus on selected determinants, and the limited quality and size of the available studies, further research is needed to comprehensively understand causality and to improve relapse prevention strategies.

Effects of Weight Loss on Endothelium and Vascular Homeostasis: Impact on Cardiovascular Risk

Available knowledge shows that obesity is associated with an impaired endothelial function and an increase in cardiovascular risk, but the mechanisms of this association are not yet fully understood. Adipose tissue dysfunction, adipocytokines production, along with systemic inflammation and associated comorbidities (e.g., diabetes and hypertension), are regarded as the primary physiological and pathological factors. Various strategies are now available for the control of excess body weight. Dietary regimens alone, or in association with bariatric surgery when indicated, are now widely used. Of particular interest is the understanding of the effect of these interventions on endothelial homeostasis in relation to cardiovascular health. Substantial weight loss resulting from both diet and bariatric surgery decreases circulating biomarkers and improves endothelial function. Extensive clinical trials and meta-analyses show that bariatric surgery (particularly gastric bypass) has more substantial and long-lasting effect on weight loss and glucose regulation, as well as on distinct circulating biomarkers of cardiovascular risk. This review summarizes the current understanding of the distinct effects of diet-induced and surgery-induced weight loss on endothelial function, focusing on the key mechanisms involved in these effects.

Symptomatic idiopathic intracranial hypertension triggered by Ramadan intermittent fasting: a case report

BACKGROUND

Idiopathic intracranial hypertension (IIH) is a disorder that primarily affects obese women of reproductive age. The exact pathogenesis of IIH is unknown though multiple etiologies have been proposed.

CASE PRESENTATION

We report a case of IIH triggered by first-time Ramadan intermittent fasting (RIF) in an 18-year-old woman. Our patient developed new onset headaches, diplopia, and pulsatile tinnitus with examination notable for bilateral papilledema and lumbar puncture revealing an elevated opening pressure. Her symptoms resolved after cessation of RIF, apart from persistent left sided tinnitus which later resolved with acetazolamide administration.

CONCLUSION

This case report uniquely illustrates that RIF may provoke symptomatic IIH. We hypothesize that a decreased concentration of glucagon-like peptide-1 (GLP-1) induced by fasting results in decreased GLP-1 receptor activation in the choroid plexus, allowing for increased CSF secretion into the ventricles invoking increased intracranial pressure (ICP). This theoretical mechanism provides further insight as to the possible underlying pathophysiology of IIH.

Changes in ghrelin, GLP-1, and PYY levels after diet and exercise in obese individuals

OBJECTIVE

Diet and exercise, which are the building blocks of obesity management, provide weight loss by creating a negative energy balance. However, the effect of energy deficit induced by long-term diet and exercise on appetite hormones remains unclear. The study was designed to determine the effect of a 12-week diet and exercise program applied to obese individuals on the levels of appetite hormones, namely, ghrelin, GLP-1, and PYY.

METHODS

A total of 62 obese individuals (BMI≥30) and 48 healthy controls (BMI 18.50-29.99) participated in the study. Appropriate diet (1000-1500 kcal/day) and exercise (at least 5000 steps/day) programs were applied to obese individuals according to age, gender, and BMI. The ghrelin, GLP-1, and PYY values of the participants were analyzed by the ELISA method and commercial kit by taking venous blood samples before and after 12 weeks of treatment.

RESULTS

While ghrelin levels of individuals decreased significantly after diet and exercise, PYY levels increased significantly. However, despite the treatment applied, the GLP-1 and PYY levels of the case group did not reach the levels of the control group.

CONCLUSION

Long-term diet and exercise intervention had a positive effect on appetite regulation hormones. It reduced ghrelin levels after treatment. Associated weight loss was facilitated. In the case group, increased satiety hormones after combined treatment supported the maintenance of body weight by increasing satiety.

Patterns and Determinants of Weight Gain among People Who Use Drugs Undergoing Treatment for Recovery in Lebanon

Substance use disorder compromises the nutritional status and the eating habits of drug users, often leading to malnutrition. Once referred for treatment, hyperphagia and poor lifestyle practices leading to weight gain are observed. This study aimed to examine the patterns and extent of weight change as well as the determinants of weight gain in a sample of drug users who were receiving treatment in Lebanon. A total of 172 male participants undergoing either rehabilitation or opioid substitution treatment (OST) were included. Multivariate regression analysis was applied to assess the effect of different variables on weight gain while adjusting for potentially confounding variables. Approximately two-thirds (65.1%) of the participants gained weight (OST: 54.3%, rehabilitation: 78.2%; p < 0.05). The mean weight gain was 5.9 kg and was mainly reported among participants in the underweight, normal, and overweight pre-treatment categories and accentuated in the rehabilitation group (OST: 2 kg, Rehabilitation: 10.6 kg). Around half of the participants moved from the normal weight category to the overweight and obese categories during treatment. Weight gain was negatively associated with the number of previous treatment attempts (Odds Ratio = 0.86; Confidence Interval: 0.74-0.99), duration of current treatment (Odds Ratio = 0.98; Confidence Interval: 0.96-0.99), and pre-treatment body mass index (BMI) (Odds Ratio = 0.88; Confidence Interval: 0.80-0.96). Investigating other nutrition and lifestyle practices, neither nutrition knowledge, food addiction, physical activity level, nor sleep quality were associated with weight gain. Treatment through drug use was associated with meaningful weight gain that might lead to health risk factors. Developing health promotion programs is crucial to enhance treatment and decrease the risk of relapse.

The role of cereal soluble fiber in the beneficial modulation of glycometabolic gastrointestinal hormones

According to cohort studies, cereal fiber, and whole-grain products might decrease risk for type 2 diabetes (T2DM), inflammatory processes, cancer, and cardiovascular diseases. These associations, mainly affect insoluble, but not soluble cereal fiber. In intervention studies, soluble fiber elicit anti-hyperglycemic and anti-inflammatory short-term effects, partially explained by fermentation to short-chain fatty acids, which acutely counteract insulin resistance and inflammation. ß-glucans lower cholesterol levels and possibly reduce liver fat. Long-term benefits are not yet shown, maybe caused by T2DM heterogeneity, as insulin resistance and fatty liver disease - the glycometabolic points of action of soluble cereal fiber - are not present in every patient. Thus, only some patients might be susceptive to fiber. Also, incretin action in response to fiber could be a relevant factor for variable effects. Thus, this review aims to summarize the current knowledge from human studies on the impact of soluble cereal fiber on glycometabolic gastrointestinal hormones. Effects on GLP-1 appear to be highly contradictory, while these fibers might lower GIP and ghrelin, and increase PYY and CCK. Even though previous results of specific trials support a glycometabolic benefit of soluble fiber, larger acute, and long-term mechanistic studies are needed in order to corroborate the results.

Circadian secretion rhythm of GLP-1 and its influencing factors

Circadian rhythm is an inherent endogenous biological rhythm in living organisms. However, with the improvement of modern living standards, many factors such as prolonged artificial lighting, sedentarism, short sleep duration, intestinal flora and high-calorie food intake have disturbed circadian rhythm regulation on various metabolic processes, including GLP-1 secretion, which plays an essential role in the development of various metabolic diseases. Herein, we focused on GLP-1 and its circadian rhythm to explore the factors affecting GLP-1 circadian rhythm and its potential mechanisms and propose some feasible suggestions to improve GLP-1 secretion.

A Synbiotic Formulation Comprising Bacillus subtilis DSM 32315 and L-Alanyl-L-Glutamine Improves Intestinal Butyrate Levels and Lipid Metabolism in Healthy Humans

The gut microbiota is a crucial modulator of health effects elicited by food components, with SCFA (short chain fatty acids), especially butyrate, acting as important mediators thereof. We therefore developed a nutritional synbiotic composition targeted at shifting microbiome composition and activity towards butyrate production. An intestinal screening model was applied to identify probiotic Bacillus strains plus various amino acids and peptides with suitable effects on microbial butyrate producers and levels. A pilot study was performed to test if the synbiotic formulation could improve fecal butyrate levels in healthy humans. A combination of Bacillus subtilis DSM (Number of German Collection of Microorganisms and Cell Cultures) 32315 plus L-alanyl-L-glutamine resulted in distinctly increased levels of butyrate and butyrate-producing taxa (Clostridium group XIVa, e.g., Faecalibacterium prausnitzii), both in vitro and in humans. Moreover, circulating lipid parameters (LDL-, and total cholesterol and LDL/HDL cholesterol ratio) were significantly decreased and further metabolic effects such as glucose-modulation were observed. Fasting levels of PYY (Peptide YY) and GLP-1 (Glucagon-like Peptide 1) were significantly reduced. In conclusion, our study indicates that this synbiotic composition may provide an effective and safe tool for stimulation of intestinal butyrate production with effects on e.g., lipid and glucose homeostasis. Further investigations in larger cohorts are warranted to confirm and expand these findings.

Practical Approaches to Treating Obesity: Patient and Healthcare Professional Perspectives

Obesity is a chronic and treatable disease carrying risk for numerous health complications, including cardiovascular disease, respiratory disease, type 2 diabetes mellitus and certain cancers. While there is a great need to address the topic in clinical practice, healthcare professionals (HCPs) often struggle to initiate conversations about weight. In this paper, guidance on how to raise and address the subject of weight with individuals is provided from an HCP and patient perspective using the 5As framework. This model facilitates advising individuals on the benefits of weight loss and supports them to develop achievable and sustainable weight management plans. With obesity rates still rising across the globe, it is imperative that more HCPs become skilled in raising and addressing the issue.

Metabolic Adaptations to Weight Loss: A Brief Review

ABSTRACT

Martínez-Gómez, MG and Roberts, BM. Metabolic adaptations to weight loss: A brief review. J Strength Cond Res XX(X): 000-000, 2021-As the scientific literature has continuously shown, body mass loss attempts do not always follow a linear fashion nor always go as expected even when the intervention is calculated with precise tools. One of the main reasons why this tends to happen relies on our body's biological drive to regain the body mass we lose to survive. This phenomenon has been referred to as "metabolic adaptation" many times in the literature and plays a very relevant role in the management of obesity and human weight loss. This review will provide insights into some of the theoretical models for the etiology of metabolic adaptation as well as a quick look into the physiological and endocrine mechanisms that underlie it. Nutritional strategies and dietetic tools are thus necessary to confront these so-called adaptations to body mass loss. Among some of these strategies, we can highlight increasing protein needs, opting for high-fiber foods or programming-controlled diet refeeds, and diet breaks over a large body mass loss phase. Outside the nutritional aspects, it might be wise to increase the physical activity and thus the energy flux of an individual when possible to maintain diet-induced body mass loss in the long term. This review will examine these protocols and their viability in the context of adherence and sustainability for the individual toward successful body mass loss.

Weight loss-induced increase in fasting ghrelin concentration is a predictor of weight regain: Evidence from the Diabetes Remission Clinical Trial (DiRECT)

AIM

To investigate whether appetite-related hormones were predictors of weight regain in the Diabetes Remission Clinical Trial (DiRECT).

MATERIALS AND METHODS

DiRECT is a cluster-randomized clinical trial, designed to assess the effect of weight loss on type 2 diabetes remission. For this post hoc analysis, data were available for 253 (147 interventions, 106 controls) individuals with type 2 diabetes (age 53.6 ± 7.5 years, body mass index 34.7 ± 4.4 kg/m2 , 59% men). Intervention participants received a 24-month weight management programme, and controls remained on usual diabetes care. Fasting plasma concentrations of leptin, ghrelin, glucagon-like peptide-1 and peptide YY were measured at baseline, 12 months and 24 months in all participants, and at 5 months in a subset of participants in the intervention (n = 56) and control groups (n = 22). Potential predictors were examined using multivariable linear regression models.

RESULTS

The intervention group lost 14.3 ± 6.0% body weight at 5 months but regained weight over time, with weight losses of 10.0 ± 7.5% at 12 months and 7.6 ± 6.3% at 24 months. Weight loss in controls was 1.1 ± 3.7% and 2.1 ± 5.0% at 12 and 24 months, respectively. Body weight increased by 2.3% (95% confidence interval [CI] 0.4, 4.1; P = 0.019) between 12 and 24 months for every 1-ng/mL increase in ghrelin between baseline and 12 months, and weight regain between 12 and 24 months was increased by 1.1% (95% CI 0.2, 2.0; P = 0.023) body weight for every 1-ng/mL increase in ghrelin at 12 months.

CONCLUSION

The rise in ghrelin (but not any other measured hormone) during diet-induced weight loss was a predictor of weight regain during follow-up, and concentrations remained elevated over time, suggesting a small but significant compensatory drive to regain weight. Attenuating the effects of ghrelin may improve weight-loss maintenance.

An Exploration of the Role of Sugar-Sweetened Beverage in Promoting Obesity and Health Disparities

PURPOSE OF REVIEW

The mechanistic role of sugar-sweetened beverage (SSB) in the etiology of obesity is undetermined. We address whether, compared to other foods, does consumption of SSB (1) automatically lead to failure to compensate for the energy it contains? (2) fail to elicit homeostatic hormone responses? (3) promote hedonic eating through activation of the brain's reward pathways? We followed the evidence to address: (4) Would restriction of targeted marketing of SSB and other unhealthy foods to vulnerable populations decrease their prevalence of obesity?

RECENT FINDINGS

The data are lacking to demonstrate that SSB consumption promotes body weight gain compared with isocaloric consumption of other beverages or foods and that this is linked to its failure to elicit adequate homeostatic hormone responses. However, more recent data have linked body weight gain to reward activation in the brain to palatable food cues and suggest that sweet tastes and SSB consumption heightens the reward response to food cues. Studies investigating the specificity of these responses have not been conducted. Nevertheless, the current data provide a biological basis to the body of evidence demonstrating that the targeted marketing (real life palatable food cues) of SSB and other unhealthy foods to vulnerable populations, including children and people of color and low socioeconomic status, is increasing their risk for obesity. While the mechanisms for the association between SSB consumption and body weight gain cannot be identified, current scientific evidence strongly suggests that proactive environmental measures to reduce exposure to palatable food cues in the form of targeting marketing will decrease the risk of obesity in vulnerable populations.

Weight Loss, but Not Dairy Composition of Diet, Moderately Affects Satiety and Postprandial Gut Hormone Patterns in Adults

BACKGROUND

Inclusion of dairy in diet patterns has been shown to have mixed effects on weight loss. A prevailing hypothesis is that dairy improves weight loss by influencing endocrine systems associated with satiety and food intake regulation.

OBJECTIVES

The objective of the current study was to evaluate the effect of weight loss with or without adequate dietary dairy on subjective and objective appetitive measures.

METHODS

Men and women who were habitual low dairy consumers (n = 65, 20-50 y) participated in a 12-wk randomized controlled feeding weight loss trial. During the 12-wk intervention, a low-dairy (<1 serving dairy/d) was compared with an adequate-dairy (3-4 servings dairy/d) diet, both with a 500-kcal deficit/d. Test days, before and at the end of the intervention, began with 2 fasting blood draws and visual analog scale (VAS) measures, followed by a standard breakfast (25% of prescribed restricted calories), 5 postbreakfast blood draws and VASs, a standard lunch (40% of restricted energy amount), and 12 postlunch blood draws and VASs. Blood samples were used for satiety hormone measurements. On a separate day when matching standard meals were consumed, an ad libitum buffet meal was provided as dinner, at a self-selected time. Meal duration and intermeal interval were recorded.

RESULTS

Weight loss (-6.1 kg), irrespective of dairy, resulted in reduced fasting insulin (-20%) and leptin (-25%), and increased fasting acylated ghrelin (+25%) and VAS desire to eat (+18%) (P < 0.05). There were no effects of dairy on objective or subjective satiety measures. Weight loss marginally reduced the intermeal interval (289 min compared with 276 min, P = 0.059) between lunch and the ad libitum buffet.

CONCLUSIONS

These results do not support the hypothesis that inclusion of dairy in long-term dietary patterns influences appetite during weight loss. Weight loss per se has a modest impact on select systems that regulate hunger and satiety.This trial was registered at clinicaltrials.gov as NCT00858312.

GLP-1 Analog Modulates Appetite, Taste Preference, Gut Hormones, and Regional Body Fat Stores in Adults with Obesity

PURPOSE

Obesity is associated with alterations in appetite, gastrointestinal hormone levels and excessive fat mass. We previously published a double-blind, placebo-controlled, randomized, 16-week trial on effects of once-daily glucagon-like peptide-1 (GLP-1) analog, liraglutide on weight, satiation, and gastric functions in obese volunteers. The aim of this substudy is to compare to placebo the effects of liraglutide on appetite, taste preference, regional body fat stores, and anthropometric measurements.

METHODS

Forty obese adults received standard instruction for weight management, monthly behavioral intervention utilizing motivational interviews, and 16-week treatment of once-daily liraglutide (escalated to 3 mg SQ daily). At baseline and 16 weeks, the following were measured: appetite and taste preferences rated every 30 min for 5 h after ingesting 300 mL Ensure®; maximal tolerated volume (MTV) with a nutrient drink test; fasting and postprandial bioactive GLP-1 (7-36) and peptide YY (PYY) levels; total and regional body fat with dual-energy X-ray absorptiometry, and waist and hip circumference.

RESULTS

Thirty-five participants (17 liraglutide; 18 placebo) completed the trial. Compared to placebo group, liraglutide group had significant reductions in MTV; prospective food consumption score; desire to eat something sweet, salty, savory or fatty; and an increase in perceived fullness. Postprandial plasma levels of GLP-1 decreased and PYY levels increased with liraglutide relative to baseline. Significant reductions in total body, trunk, and upper and lower body fat without reduction in lean body mass were observed.

CONCLUSION

Liraglutide 3 mg SQ modulates appetite, taste preference, gut hormones, and regional body fat stores in adults with obesity without reduction in lean body mass.

The role of appetite-related hormones, adaptive thermogenesis, perceived hunger and stress in long-term weight-loss maintenance: a mixed-methods study

BACKGROUND/OBJECTIVES

Weight-loss maintenance is challenging, and few succeed in the long term. This study aimed to explain how appetite-related hormones, adaptive thermogenesis, perceived hunger and stress influence weight-loss maintenance.

SUBJECTS/METHODS

Fifteen adult women (age, 46.3 ± 9.5 years; BMI, 39.4 ± 4.3 kg/m²) participated in a 24-month intervention, which included 3-5 months total diet replacement (825-853 kcal/d). Body weight and composition (Magnetic Resonance Imaging), resting metabolic rate (indirect calorimetry), and fasting plasma concentration of leptin, ghrelin, glucagon-like peptide-1 (GLP-1), peptide YY (PYY), and growth differentiation factor 15 (GDF-15) were measured at baseline and after weight loss, around 6 months. Perceptions relating to weight-loss maintenance were explored using qualitative interviews.

RESULTS

Mean (SD) changes in body weight (-13.8 ± 6.3 kg) and total adipose tissue (-11.5 ± 4.9 kg) were significant (P < 0.001). Weight loss was associated with a significant reduction in resting metabolic rate (-291 ± 226 kcal/day, P < 0.001) and adaptive thermogenesis (-150 ± 162 kcal/day, P = 0.003), reduction in leptin (P < 0.001) and GLP-1 (P = 0.015), an increase in ghrelin (P < 0.001), and no changes in PYY and GDF-15. Weight regain between 6 and 24 months (6.1 ± 6.3 kg, P < 0.05) was negatively correlated with GLP-1 at baseline (r = −0.7, P = 0.003) and after weight loss (r = -0.7, P = 0.005). Participants did not report increased hunger after weight loss, and stress-related/emotional eating was perceived as the main reason for regain.

CONCLUSIONS

Weight regain is more likely with lower fasting GLP-1 at baseline and following weight loss, but psychological aspects of eating behaviour appear as important in attenuating weight-loss maintenance.

Postprandial levels of GLP-1, GIP and glucagon after 2 years of weight loss with a Paleolithic diet: a randomised controlled trial in healthy obese women

Objective To investigate how weight loss by different diets impacts postprandial levels of glucagon-like peptide 1 (GLP-1), glucose-dependent insulinotropic polypeptide (GIP) and glucagon. Methods In this single-centre, parallel group 2-year trial, 70 healthy postmenopausal obese women were randomised to the Paleolithic diet or a healthy control diet based on Nordic Nutrition Recommendations. Both diets were without calorie restriction. The primary outcome was the change in fat mass. Here, secondary analyses on GLP-1, GIP and glucagon measured during an OGTT are described. Results In the Paleolithic diet group, mean weight loss compared to baseline was 11% at 6 months and 10% at 24 months. In the control diet group, mean weight loss was 6% after 6 and 24 months (P = 0.0001 and P = 0.049 for the comparison between groups at 6 and 24 months respectively). Compared to baseline, the mean incremental area under the curve (iAUC) for GLP-1 increased by 34 and 45% after 6 and 24 months in the Paleolithic diet group and increased by 59% after 24 months in the control diet group. The mean iAUC for GIP increased only in the Paleolithic diet group. The area under the curve (AUC) for glucagon increased during the first 6 months in both groups. The fasting glucagon increase correlated with the β-hydroxybutyrate increase. Conclusions Weight loss caused an increase in postprandial GLP-1 levels and a further rise occurred during weight maintenance. Postprandial GIP levels increased only after the Paleolithic diet. Reduced postprandial glucagon suppression may be caused by a catabolic state.

Investigating the effect of sex and ketosis on weight-loss-induced changes in appetite

BACKGROUND

Diet-induced weight loss (WL) is usually accompanied by increased appetite, a response that seems to be absent when ketogenic diets are used. It remains unknown if sex modulates the appetite suppressant effect of ketosis.

OBJECTIVE

The aim of this study was to examine if sex modulates the impact of WL-induced changes in appetite and if ketosis alters these responses.

METHODS

Ninety-five individuals (55 females) with obesity (BMI [kg/m 2]: 37  ± 4) underwent 8 wk of a very-low-energy diet, followed by 4 wk of refeeding and weight stabilization. Body composition, plasma concentration of β-hydroxybutyrate (β-HB) and appetite-related hormones (active ghrelin, active glucagon-like peptide 1 [GLP-1], total peptide YY [PYY], cholecystokinin and insulin), and subjective feelings of appetite were measured at baseline, week 9 in ketosis, and week 13 out of ketosis.

RESULTS

The mean WL at week 9 was 17% for males and 15% for females, which was maintained at week 13. Weight, fat, and fat-free mass loss were greater in males (P < 0.001 for all) and the increase in β-HB at week 9 higher in females (1.174 ± 0.096 compared with 0.783 ± 0.112 mmol/L, P = 0.029). Basal and postprandial GLP-1 and postprandial PYY (all P < 0.05) were significantly different for males and females. There were no significant sex × time interactions for any other appetite-related hormones or subjective feelings of appetite. At week 9, basal GLP-1 was decreased only in males (P < 0.001), whereas postprandial GLP-1 was increased only in females (P < 0.001). No significant changes in postprandial PYY were observed over time for either sex.

CONCLUSIONS

Ketosis appears to have a greater beneficial impact on GLP-1 in females. However, sex does not seem to modulate the changes in the secretion of other appetite-related hormones, or subjective feelings of appetite, seen with WL, regardless of the ketotic state. This trial was registered at clinicaltrials.gov as NCT01834859.

Metabolic adaptations during negative energy balance and their potential impact on appetite and food intake

This review examines the metabolic adaptations that occur in response to negative energy balance and their potential putative or functional impact on appetite and food intake. Sustained negative energy balance will result in weight loss, with body composition changes similar for different dietary interventions if total energy and protein intake are equated. During periods of underfeeding, compensatory metabolic and behavioural responses occur that attenuate the prescribed energy deficit. While losses of metabolically active tissue during energy deficit result in reduced energy expenditure, an additional down-regulation in expenditure has been noted that cannot be explained by changes in body tissue (e.g. adaptive thermogenesis). Sustained negative energy balance is also associated with an increase in orexigenic drive and changes in appetite-related peptides during weight loss that may act as cues for increased hunger and food intake. It has also been suggested that losses of fat-free mass (FFM) could also act as an orexigenic signal during weight loss, but more data are needed to support these findings and the signalling pathways linking FFM and energy intake remain unclear. Taken together, these metabolic and behavioural responses to weight loss point to a highly complex and dynamic energy balance system in which perturbations to individual components can cause co-ordinated and inter-related compensatory responses elsewhere. The strength of these compensatory responses is individually subtle, and early identification of this variability may help identify individuals that respond well or poorly to an intervention.

Compensation in response to energy deficits induced by exercise or diet

Obesity is an extremely resilient condition. Weight loss is most challenging, and weight recidivism is rampant. There is accumulating evidence highlighting that energy deficits meant to produce increased mobilization of energy stores trigger a number of somewhat persistent adaptations that together increase the drive to eat and decrease energy output. These adaptations ostensibly enable a context where the likelihood of energy compensation is heightened. In fact, energy compensation is present for both diet and exercise induced energy deficits although at different magnitudes. For the most part, the energy compensation in response to exercise induced energy deficits seems to be larger. Interestingly, energy compensation appears to be greater for longer interventions, an effect independent of whether the energy deficit is induced through diet or exercise. The latter suggests that the increased drive to eat and the reduced energy expenditure that accompany weight loss might be successfully fought off initially. However, with time there seems to be increasing erosion of the behaviours that initially opposed adaptations to weight loss and increased energy compensation progressively sets in. Under such conditions, it would seem prudent to propose weight loss targets that align with a level of behaviour modifications that can be sustained indefinitely.

Impact of gastric emptying and small intestinal transit on blood glucose, intestinal hormones, glucose absorption in the morbidly obese

This study evaluated gastric emptying (GE) and small intestinal (SI) transit in people with morbid obesity and their relationships to glycaemia, incretin hormones, and glucose absorption METHODS: GE and caecal arrival time (CAT) of a mixed meal were assessed in 22 morbidly obese (50.2 ± 2.5 years; 13 F:9 M; BMI: 48.6 ± 1.8 kg/m2) and 10 lean (38.6 ± 8.4 years; 5 F:5 M; BMI: 23.9 ± 0.7 kg/m2) subjects, using scintigraphy. Blood glucose, plasma 3-O-methylglucose, insulin, glucagon, glucose-dependent insulinotropic polypeptide (GIP) and glucagon-like peptide-1 (GLP-1) were measured. Insulin sensitivity and resistance were also quantified RESULTS: When compared with lean subjects, GE (t50: 60.7 ± 6.5 vs. 41.1 ± 7.3 min; P  = 0.04) and CAT (221.5 ± 9.8 vs. 148.0 ± 7.1 min; P =  0.001) of solids were prolonged in morbid obesity. Postprandial rises in GIP (P = 0.001), insulin (P  = 0.02), glucose (P = 0.03) and 3-O-methylglucose (P = 0.001) were less. Whereas GLP-1 increased at 45 mins post-prandially in lean subjects, there was no increase in the obese (P  = 0.04). Both fasting (P = 0.045) and postprandial (P = 0.012) plasma glucagon concentrations were higher in the obese CONCLUSIONS: GE and SI transit are slower in the morbidly obese, and associated with reductions in postprandial glucose absorption, and glycaemic excursions, as well as plasma GIP and GLP-1.

Timeline of changes in appetite during weight loss with a ketogenic diet

Background/objective:

Diet-induced weight loss (WL) leads to increased hunger and reduced fullness feelings, increased ghrelin and reduced satiety peptides concentration (glucagon-like peptide-1 (GLP-1), cholecystokinin (CCK) and peptide YY (PYY)). Ketogenic diets seem to minimise or supress some of these responses. The aim of this study was to determine the timeline over which changes in appetite occur during progressive WL with a ketogenic very-low-energy diet (VLED).

Subjects/methods:

Thirty-one sedentary adults (18 men), with obesity (body mass index: 37±4.5 kg m⁻²) underwent 8 weeks (wks) of a VLED followed by 4 wks of weight maintenance. Body weight and composition, subjective feelings of appetite and appetite-related hormones (insulin, active ghrelin (AG), active GLP-1, total PYY and CCK) were measured in fasting and postprandially, at baseline, on day 3 of the diet, 5 and 10% WL, and at wks 9 and 13. Data are shown as mean±s.d.

Results:

A significant increase in fasting hunger was observed by day 3 (2±1% WL), (P<0.01), 5% WL (12±8 days) (P<0.05) and wk 13 (17±2% WL) (P<0.05). Increased desire to eat was observed by day 3 (P<0.01) and 5% WL (P<0.05). Postprandial prospective food consumption was significantly reduced at wk 9 (16±2% WL) (P<0.01). Basal total PYY was significantly reduced at 10% WL (32±8 days) (P<0.05). Postprandial active GLP-1 was increased at 5% WL (P<0.01) and CCK reduced at 5 and 10% WL (P<0.01, for both) and wk 9 (P<0.001). Basal and postprandial AG were significantly increased at wk 13 (P<0.001, both).

Conclusions:

WL with a ketogenic VLED transiently increases the drive to eat up to 3 weeks (5% WL). After that, and while participants are ketotic, a 10–17% WL is not associated with increased appetite. However, hunger feelings and AG concentrations increase significantly from baseline, once refeeding occurs.

Effect of 24-h severe energy restriction on appetite regulation and ad libitum energy intake in lean men and women

BACKGROUND

Intermittent severe energy restriction (SER) can induce substantial weight loss, but the appetite regulatory responses to SER are unknown and may dictate long-term dietary adherence.

OBJECTIVE

We determined the effect of 24-h SER on appetite regulation, metabolism, and energy intake.

DESIGN

Eighteen lean men and women completed two 3-d trials in randomized, counterbalanced order. On day 1 subjects consumed standardized diets containing 100% (mean ± SD: 9.3 ± 1.3 MJ; energy balance) or 25% [2.3 ± 0.3 MJ; energy restriction (ER)] of energy requirements. On day 2, a standardized breakfast was consumed, with plasma concentrations of acylated ghrelin, glucagon-like peptide 1, insulin, glucose, and nonesterified fatty acids determined for 4 h. Ad libitum energy intake was assessed at lunch and dinner with subjective appetite and resting metabolism assessed throughout. On day 3, ad libitum energy intake was assessed at breakfast and by weighed food records.

RESULTS

Energy intake was 7% greater on day 2 (P < 0.05) during ER but not significantly different on day 3 (P = 0.557). Subjective appetite was greater during ER on the morning of day 2 (P < 0.05) but was not significantly different thereafter (P > 0.145). During ER, postprandial concentrations of acylated ghrelin were lower (P < 0.05), whereas glucose (P < 0.05) and nonesterified fatty acids (P < 0.0001) were higher. Postprandial glucagon-like peptide 1_7-36 (P = 0.784) and insulin (P = 0.06) concentrations were not significantly different between trials. Energy expenditure was lower during ER in the morning (P < 0.01).

CONCLUSIONS

In lean young adults, 24-h SER transiently elevated subjective appetite and marginally increased energy intake, but hormonal appetite markers did not respond in a manner indicative of hyperphagia. These results suggest that intermittent SER might be useful to attenuate energy intake and control body weight in this population. This trial was registered at www.clinicaltrials.gov.uk as NCT02696772.

Increased GLP-1 response to oral glucose in pre-pubertal obese children

BACKGROUND

Gastrointestinal hormones, such as glucagon-like peptide (GLP-1), have been hypothesized to play a role in the pathogenesis of obesity-related complications. However, few data are available in youth. The objective of this study was to investigate the GLP-1 response to oral glucose load in obese pre-pubertal children and its relationship with insulin secretion.

METHODS

Ten pre-pubertal obese children [five boys; 10.5±1.6 years; body mass index-standard deviation score (BMI-SDS): 2.2±0.5] and 10 controls (eight boys; 9.9±1.2 years; BMI-SDS: -0.7±0.5) underwent a modified oral glucose tolerance test (OGTT) to evaluate post-load glucose, insulin and GLP-1 responses. Insulin sensitivity [homeostasis model assessment of insulin resistance (HOMA-IR), whole body insulin sensitivity index (WBISI)] and secretion [HOMA-beta, insulinogenic index (IGI)] indexes, area under the curve (AUC) for glucose, insulin and GLP-1 were calculated.

RESULTS

In obese children GLP-1 AUC values were higher and correlated with BMI-SDS (r=0.45; p=0.04), HOMA-IR (r=0.53; p=0.01) and fasting glucose (r=0.68; p=0.001).

CONCLUSIONS

Obese children showed an increased GLP-1 response to oral glucose. These changes might likely represent a compensatory mechanism to avoid post-prandial hyperglycemia and allow a normal glucose tolerance.

No effect of 24 h severe energy restriction on appetite regulation and ad libitum energy intake in overweight and obese males

BACKGROUND/OBJECTIVES

Long-term success of weight loss diets might depend on how the appetite regulatory system responds to energy restriction (ER). This study determined the effect of 24 h severe ER on subjective and hormonal appetite regulation, subsequent ad libitum energy intake and metabolism.

SUBJECTS/METHODS

In randomised order, eight overweight or obese males consumed a 24 h diet containing either 100% (12105 (1174 kJ; energy balance; EB) or 25% (3039 (295) kJ; ER) of estimated daily energy requirements (EER). An individualised standard breakfast containing 25% of EER (3216 (341) kJ) was consumed the following morning and resting energy expenditure, substrate utilisation and plasma concentrations of acylated ghrelin, glucagon-like peptide-1 (GLP-1_7-36), glucose-dependant insulinotropic peptide (GIP_1-42), glucose, insulin and non-esterified fatty acid (NEFA) were determined for 4 h after breakfast. Ad libitum energy intake was assessed in the laboratory on day 2 and via food records on day 3. Subjective appetite was assessed throughout.

RESULTS

Energy intake was not different between trials for day 2 (EB: 14946 (1272) kJ; ER: 15251 (2114) kJ; P=0.623), day 3 (EB: 10580 (2457) kJ; 10812 (4357) kJ; P=0.832) or day 2 and 3 combined (P=0.693). Subjective appetite was increased during ER on day 1 (P<0.01), but was not different between trials on day 2 (P>0.381). Acylated ghrelin, GLP-1_7-36 and insulin were not different between trials (P>0.104). Post-breakfast area under the curve (AUC) for NEFA (P<0.05) and GIP_1-42 (P<0.01) were greater during ER compared with EB. Fat oxidation was greater (P<0.01) and carbohydrate oxidation was lower (P<0.01) during ER, but energy expenditure was not different between trials (P=0.158).

CONCLUSIONS

These results suggest that 24 h severe ER does not affect appetite regulation or energy intake in the subsequent 48 h. This style of dieting may be conducive to maintenance of a negative EB by limiting compensatory eating behaviour, and therefore may assist with weight loss.

Plasma levels of glucagon-like peptide 1 and markers of obesity among young and healthy adults

OBJECTIVE

Glucagon-like peptide 1 (GLP-1)-related pathways may partially explain the strong relationship between obesity and type 2 diabetes. We therefore aimed to evaluate the relationships between fasting GLP-1 levels, body fat mass and other obesity markers in a large sample of young and healthy adults.

DESIGN AND PATIENTS

Our population-based study included 2096 individuals aged 24-44. Exclusion criteria were prevalent cardiovascular disease, diabetes or a body mass index (BMI) >35 kg/m(2) . Body fat mass was obtained by bioelectrical impedance analysis. Multivariable linear regression models were constructed to assess the relationships of GLP-1 with various measures of body composition.

RESULTS

Median age of our population was 37 years, median BMI 24·1 kg/m(2) and median body fat 25·1%. A strong positive correlation was observed in age-adjusted models between GLP-1 and fat mass in men (β (95% confidence interval) 1·38 (0·69; 2·07), P < 0·001) and women (1·27 (0·65; 1·89), P < 0·001) as well as fully adjusted models including BMI in men [0·87 (0·27; 1·46), P < 0·01] but not women [0·29 (-0·07; 0·64), P = 0·11]. The relationships of GLP-1 with BMI for men and women [0·00 (-0·34; 0·34), P = 0·99] [-0·02 (-0·28; 0·25), P = 0·91] and waist circumference [0·43 (-0·45; 1·30), P = 0·34] [0·37 (-0·44; 1·18), P = 0·37], respectively, were not significant after multivariable adjustment including fat mass.

CONCLUSION

Among young and healthy adults, GLP-1 levels are strongly and independently related to body fat mass especially in men but not BMI or waist circumference. These results raise the hypothesis that GLP-1 may be implicated in body fat mass regulation.

Calorie Restriction and Matched Weight Loss From Exercise: Independent and Additive Effects on Glucoregulation and the Incretin System in Overweight Women and Men

OBJECTIVE

It is not known whether calorie restriction (CR) has additive benefits to those from exercise (EX)-induced weight loss. We hypothesized that weight loss from CR and EX (CREX) improves insulin sensitivity more than matched weight loss induced by EX or CR alone and that the incretin system may be involved in adaptations to CR.

RESEARCH DESIGN AND METHODS

Sedentary, overweight men and women (n = 52, 45-65 years of age) were randomized to undergo 6-8% weight loss by using CR, EX, or CREX. Glucose, insulin, C-peptide, insulin sensitivity, and incretin hormones (glucagon-like peptide 1 [GLP-1] and glucose-dependent insulinotropic polypeptide [GIP]) were measured during frequently sampled oral glucose tolerance tests (FSOGTTs). Incretin effects on insulin secretion were measured by comparing insulin secretion rates from the FSOGTTs to those from a glycemia-matched glucose infusion.

RESULTS

Despite similar weight losses in all groups, insulin sensitivity index values increased twofold more in the CREX group (2.09 ± 0.35 μM/kg/pM × 100) than in the CR (0.89 ± 0.39 μM/kg/pM × 100) and EX (1.04 ± 0.39 μM/kg/pM × 100) groups. Postprandial GLP-1 concentrations decreased only in the CR group (P = 0.04); GIP concentrations decreased in all groups. Incretin effects on insulin secretion were unchanged.

CONCLUSIONS

CR and EX have additive beneficial effects on glucoregulation. Furthermore, the adaptations to CR may involve reductions in postprandial GLP-1 concentrations. These findings underscore the importance of promoting both CR and EX for optimal health. However, because data from participants who withdrew from the study and from those who did not adhere to the intervention were excluded, the results may be limited to individuals who are capable of adhering to a healthy lifestyle intervention.

The gut sensor as regulator of body weight

The gastrointestinal (GI) tract comprises a large endocrine organ that regulates not only nutrient sensing and metabolising but also satiety and energy homeostasis. More than 20 hormones secreted from the stomach, intestine, and pancreas as well as signaling mediators of the gut microbiome are involved in this process. A better understanding of how related pathways affect body weight and food intake will help us to find new strategies and drugs to treat obesity. For example, weight loss secondary to lifestyle intervention is often accompanied by unfavorable changes in multiple GI hormones, which may cause difficulties in maintaining a lower body weight status. Conversely, bariatric surgery favorably changes the hormone profile to support improved satiety and metabolic function. This partially explains stronger sustained body weight reduction resulting in better long-term results of improved metabolic functions. This review focuses on GI hormones and signaling mediators of the microbiome involved in satiety regulation and energy homeostasis and summarizes their changes following weight loss. Furthermore, the potential role of GI hormones as anti-obesity drugs is discussed.

Physiological adaptations to weight loss and factors favouring weight regain

Obesity is a major global health problem and predisposes individuals to several comorbidities that can affect life expectancy. Interventions based on lifestyle modification (for example, improved diet and exercise) are integral components in the management of obesity. However, although weight loss can be achieved through dietary restriction and/or increased physical activity, over the long term many individuals regain weight. The aim of this article is to review the research into the processes and mechanisms that underpin weight regain after weight loss and comment on future strategies to address them. Maintenance of body weight is regulated by the interaction of a number of processes, encompassing homoeostatic, environmental and behavioural factors. In homoeostatic regulation, the hypothalamus has a central role in integrating signals regarding food intake, energy balance and body weight, while an 'obesogenic' environment and behavioural patterns exert effects on the amount and type of food intake and physical activity. The roles of other environmental factors are also now being considered, including sleep debt and iatrogenic effects of medications, many of which warrant further investigation. Unfortunately, physiological adaptations to weight loss favour weight regain. These changes include perturbations in the levels of circulating appetite-related hormones and energy homoeostasis, in addition to alterations in nutrient metabolism and subjective appetite. To maintain weight loss, individuals must adhere to behaviours that counteract physiological adaptations and other factors favouring weight regain. It is difficult to overcome physiology with behaviour. Weight loss medications and surgery change the physiology of body weight regulation and are the best chance for long-term success. An increased understanding of the physiology of weight loss and regain will underpin the development of future strategies to support overweight and obese individuals in their efforts to achieve and maintain weight loss.

Calorie Restriction and Matched Weight Loss From Exercise: Independent and Additive Effects on Glucoregulation and the Incretin System in Overweight Women and Men

OBJECTIVE

It is not known whether calorie restriction (CR) has additive benefits to those from exercise (EX)-induced weight loss. We hypothesized that weight loss from CR and EX (CREX) improves insulin sensitivity more than matched weight loss induced by EX or CR alone and that the incretin system may be involved in adaptations to CR.

RESEARCH DESIGN AND METHODS

Sedentary, overweight men and women (n = 52, 45-65 years of age) were randomized to undergo 6-8% weight loss by using CR, EX, or CREX. Glucose, insulin, C-peptide, insulin sensitivity, and incretin hormones (glucagon-like peptide 1 [GLP-1] and glucose-dependent insulinotropic polypeptide [GIP]) were measured during frequently sampled oral glucose tolerance tests (FSOGTTs). Incretin effects on insulin secretion were measured by comparing insulin secretion rates from the FSOGTTs to those from a glycemia-matched glucose infusion.

RESULTS

Despite similar weight losses in all groups, insulin sensitivity index values increased twofold more in the CREX group (2.09 ± 0.35 μM/kg/pM × 100) than in the CR (0.89 ± 0.39 μM/kg/pM × 100) and EX (1.04 ± 0.39 μM/kg/pM × 100) groups. Postprandial GLP-1 concentrations decreased only in the CR group (P = 0.04); GIP concentrations decreased in all groups. Incretin effects on insulin secretion were unchanged.

CONCLUSIONS

CR and EX have additive beneficial effects on glucoregulation. Furthermore, the adaptations to CR may involve reductions in postprandial GLP-1 concentrations. These findings underscore the importance of promoting both CR and EX for optimal health. However, because data from participants who withdrew from the study and from those who did not adhere to the intervention were excluded, the results may be limited to individuals who are capable of adhering to a healthy lifestyle intervention.

Role of rs6923761 gene variant in glucagon-like peptide 1 receptor in basal GLP-1 levels, cardiovascular risk factor and serum adipokine levels in naïve type 2 diabetic patients

BACKGROUND

Role of GLP-1 variants on basal GLP-1 levels, body weight and cardiovascular risk factors remains unclear in patients with diabetes mellitus type 2.

OBJECTIVE

Our aim was to analyze the effects of rs6923761 GLP-1 receptor polymorphism on body weight, cardiovascular risk factors, basal GLP-1 levels and serum adipokine levels in naïve patients with diabetes mellitus type 2.

DESIGN

A sample of 104 naïve patients with diabetes mellitus type 2 was enrolled in a prospective way. Basal fasting glucose, c-reactive protein (CRP), insulin, insulin resistance (HOMA), total cholesterol, LDL-cholesterol, HDL-cholesterol, triglycerides concentration, basal GLP-1, HbA1c and adipokines (leptin, adiponectin, resistin) levels were determined. Weights, body mass index, waist circumference, fat mass by bioimpedance and blood pressure measures were measured.

RESULTS

Forty-nine patients (47.1%) had the genotype GG and 55 (52.9%) diabetic subjects had the next genotypes; GA (44 patients, 42.3%) or AA (11 study subjects, 10.6%) (second group). In A allele carriers, basal GLP-1 levels were higher than non-carriers (2.9 ± 2.1 ng/ml; p < 0.05). No differences were detected between both genotype groups.

CONCLUSION

Our cross-sectional study revealed an association between the rs6923761 GLP-1 receptor polymorphism (A allele carriers) and basal GLP-1 levels in naïve patients with diabetes mellitus type 2.

Do ketogenic diets really suppress appetite? A systematic review and meta-analysis

Very-low-energy diets (VLEDs) and ketogenic low-carbohydrate diets (KLCDs) are two dietary strategies that have been associated with a suppression of appetite. However, the results of clinical trials investigating the effect of ketogenic diets on appetite are inconsistent. To evaluate quantitatively the effect of ketogenic diets on subjective appetite ratings, we conducted a systematic literature search and meta-analysis of studies that assessed appetite with visual analogue scales before (in energy balance) and during (while in ketosis) adherence to VLED or KLCD. Individuals were less hungry and exhibited greater fullness/satiety while adhering to VLED, and individuals adhering to KLCD were less hungry and had a reduced desire to eat. Although these absolute changes in appetite were small, they occurred within the context of energy restriction, which is known to increase appetite in obese people. Thus, the clinical benefit of a ketogenic diet is in preventing an increase in appetite, despite weight loss, although individuals may indeed feel slightly less hungry (or more full or satisfied). Ketosis appears to provide a plausible explanation for this suppression of appetite. Future studies should investigate the minimum level of ketosis required to achieve appetite suppression during ketogenic weight loss diets, as this could enable inclusion of a greater variety of healthy carbohydrate-containing foods into the diet.

Diurnal rhythms of plasma GLP-1 levels in normal and overweight/obese subjects: lack of effect of weight loss

Food intake is regulated by not only neurohormonal, but also social, educational, and even cultural factors. Within the former, there is a complex interaction between orexigenic (ghrelin) and anorexigenic (glucagon-like peptide-1 (GLP-1)) factors in order to adjust the food intake to caloric expenditure; however, the number of subjects that are unable to properly balance appetite and body weight is increasing continuously. A loss of circadian or diurnal coordination of any of these factors may be implied in this situation. Special attention has retrieved GLP-1 due to its usefulness as a therapeutic agent against obesity and related alterations. Thus, the objective of the present study was to compare GLP-1 diurnal synthesis between normal weight and overweight/obese subjects, and to evaluate whether weight loss can restore the synthesis rhythms of GLP-1. Three groups of 25 subjects were divided attending to their body mass index (BMI) in normal weight, overweight, or obese subjects. Diurnal (5 points) GLP-1 levels were analyzed. Secondly, an intervention (behavioral-dietary treatment) study was conducted to analyze the effect of weight loss on plasma GLP-1 concentrations. Our results showed that baseline GLP-1 level was significantly lower in normal weight subjects (p = 0.003); furthermore, our cosinor analysis revealed a higher amplitude (p = 0.040) and daily GLP-1 variation (47%) in these subjects. In fact, our ANOVA data showed a lack of rhythmicity in overweight/obese patients. Weight loss was not able to restore a diurnal rhythm of plasma GLP-1 levels. In summary, the present work shows a disruption of diurnal GLP-1 levels in overweight/obese subjects, which worsen as body fat progresses. The attenuation of the GLP-1 synthesis rhythms may be important to understand the impairment of food intake regulation in overweight/obese subjects.

Postprandial plasma incretin hormones in exercise-trained versus untrained subjects

INTRODUCTION

After food ingestion, the incretin hormones, glucagon-like peptide-1 (GLP-1) and glucose-dependent insulinotropic polypeptide (GIP), are secreted by the intestines into circulation where they act on the pancreas to promote insulin secretion. We evaluated the hypothesis that low postprandial plasma insulin levels in lean exercise-trained individuals are associated with low concentrations of incretin hormones.

METHODS

A cross-sectional study was performed to compare postprandial incretin hormone levels in lean endurance exercise-trained individuals (EX; n = 14, ≥40 yr) and age- and sex-matched, nonobese, sedentary control subjects (CON, n = 14). The main outcome measures were GLP-1, GIP, insulin, and glucose incremental areas under the curve (AUC) as measured in plasma samples collected during a 2-h,75-g oral glucose tolerance test (OGTT).

RESULTS

The EX group had lower body fat percentage (14.6% ± 1.1% vs 23.3% ± 1.7%, P = 0.0002) and higher maximal oxygen uptake (53 ± 2 vs 34 ± 2, P < 0.0001) than CON. Glucose AUC did not differ between groups (P = 0.20). Insulin AUC was lower in EX (2.5 ± 0.5 vs 4.2 ± 1.2 μU·mL·1000 min, P = 0.02). No differences were observed between groups (EX and CON, respectively) for GLP-1 AUC (3.5 ± 0.7 vs 4.1 ± 1.1 pmol·min·100 L, P = 0.61) or GIP AUC (19.2 ± 1.4 vs 18.0 ± 1.4 pg·min·1000 mL; P = 0.56). In CON, insulin AUC was correlated with AUC for GLP-1 (r = 0.53, P = 0.05) and GIP (r = 0.71, P = 0.004), but no such correlations were observed in EX (both P ≥ 0.67).

CONCLUSIONS

Low postprandial insulin levels in lean exercise-trained individuals are not attributable to lower incretin hormone concentrations. However, exercise may decrease the dependency of postprandial insulin levels on incretin hormones.

Nutrient-induced intestinal adaption and its effect in obesity

Obese and lean individuals respond differently to nutrients with changes in digestion, absorption and hormone release. This may be a result of differences in intestinal epithelial morphology and function driven by the hyperphagia or the type of diet associated with obesity. It is well known that the maintenance and growth of the intestine is driven by the amount of luminal nutrients, with high nutrient content resulting in increases in cell number, villi length and crypt depth. In addition, the type of nutrient appears to contribute to alterations in the morphology and function of the epithelial cells. This intestinal adaptation may be what is driving the differences in nutrient processing in lean versus obese individuals. This review describes how nutrients may be able to induce changes in intestinal epithelial cell proliferation, differentiation and function and the link between intestinal adaptation and obesity.

Body weight loss, reduced urge for palatable food and increased release of GLP-1 through daily supplementation with green-plant membranes for three months in overweight women

The frequency of obesity has risen dramatically in recent years but only few effective and safe drugs are available. We investigated if green-plant membranes, previously shown to reduce subjective hunger and promote satiety signals, could affect body weight when given long-term. 38 women (40-65 years of age, body mass index 25-33 kg/m(2)) were randomized to dietary supplementation with either green-plant membranes (5 g) or placebo, consumed once daily before breakfast for 12 weeks. All individuals were instructed to follow a three-meal paradigm without any snacking between the meals and to increase their physical activity. Body weight change was analysed every third week as was blood glucose and various lipid parameters. On days 1 and 90, following intake of a standardized breakfast, glucose, insulin and glucagon-like peptide 1 (GLP-1) in plasma were measured, as well as subjective ratings of hunger, satiety and urge for different palatable foods, using visual analogue scales. Subjects receiving green-plant membranes lost significantly more body weight than did those on placebo (p < 0.01). Mean weight loss with green-plant extract was 5.0 ± 2.3 kg compared to 3.5 ± 2.3 kg in the control group. Consumption of green-plant membranes also reduced total and LDL-cholesterol (p < 0.01 and p < 0.05 respectively) compared to control. Single-meal tests performed on day 1 and day 90 demonstrated an increased postprandial release of GLP-1 and decreased urge for sweet and chocolate on both occasions in individuals supplemented with green-plant membranes compared to control. Waist circumference, body fat and leptin decreased in both groups over the course of the study, however there were no differences between the groups. In conclusion, addition of green-plant membranes as a dietary supplement once daily induces weight loss, improves obesity-related risk-factors, and reduces the urge for palatable food. The mechanism may reside in the observed increased release of GLP-1.

The effect of 'sleep high and train low' on weight loss in overweight Chinese adolescents: study protocol for a randomized controlled trial

Background

Exercise and diet are the cornerstones for the treatment of obesity in obese children and adolescents. However, compensatory changes in appetite and energy expenditure elicited by exercise and dieting make it hard to maintain a reduced weight over the longterm. The anorexic effect of hypoxia can be potentially utilized to counteract this compensatory increase, thereby enhancing the success of weight loss. The purpose of the study is to assess the effectiveness of four week intermittent hypoxia exposure added to a traditional exercise and diet intervention on inducing short- and longterm weight loss in obese adolescents.

Methods/Design

In this randomized parallel group controlled clinical trial, 40 obese adolescents (20 boys and 20 girls, 11 to 15-years-old), will be recruited from a summer weight loss camp at the Shanghai University of Sport, China. Participants will be stratified by gender and randomly assigned to either the control group or the hypoxia group. During the four-week intervention period, both groups will exercise and eat a balanced diet. Additionally, the control group will sleep in normal conditions, while the hypoxia group will sleep in a normobaric hypoxia chamber (sleep high and train low). The primary outcome will be body composition and the main secondary outcomes will be the circulating levels of appetite regulatory gastrointestinal hormones. All the outcome measures will be assessed at baseline, after the four-week intervention, and at two months follow-up.

Discussion

Our study will be the first to evaluate the effectiveness of ‘sleep high and train low’ on short- and longterm weight loss among obese adolescents. A potential mechanism for the appetite regulatory effect of hypoxia will also be explored. The results of the study will provide an evidence-based recommendation for the use of hypoxia in a weight loss intervention among obese children and adolescents. Furthermore, the clarification of mechanisms leading to weight loss in ‘sleep high and train low’ might provide information for the development of new strategies in combating obesity.

Trial registration

This trial was registered on 10 January 2014 at the Chinese Clinical Trial Registry with the registration number: ChiCTR-TRC-14004106.

Nutrient-specific feeding and endocrine effects of jejunal infusions in obese animals

Intestinal nutrient infusions result in variable decreases in food intake and body weight based on the nutrient type and the specific intestinal infusion site. We previously found that intrajejunal infusions of a fatty acid and glucose, but not casein hydrolysate, decreases food intake and body weight in lean chow-fed laboratory rats. To test whether obese, high fat-fed animals would show similar decreases in food intake and body weight in response to intrajejunal infusions of the same nutrients, equal kilocalorie loads of these nutrients (11.4 kcal) or vehicle were infused into the jejunum of obese, high fat-fed male Sprague-Dawley rats over 7 h/day for 5 consecutive days. Food intake was continuously monitored, and body weight was measured daily. After the infusion on the final day, rats were killed and plasma was collected. Similar to lean chow-fed rats, intrajejunal infusions of linoleic acid (LA) and glucose (Glu), but not casein hydrolysate (Cas), suppressed food intake with no compensatory increase in food intake after the infusion period. In contrast to lean chow-fed rats, only the LA, and not the Glu or Cas, produced decreases in body weight in the obese high fat-fed rat. There also were no differences in plasma glucagon-like peptide-1 levels in any of the nutrient infusion groups compared with saline infusion. These results suggest that there is a differential response to the same nutrients in lean vs. obese animals.

Glucagon-like peptide-1 secretory function as an independent determinant of blood pressure: analysis in the Tanno-Sobetsu study

Aims

Roles of glucagon-like peptide-1 (GLP-1) in extra-pancreatic tissues remain unclear. The aim of this study was to examine determinants of GLP-1 secretory function and possible contribution of GLP-1 to blood pressure (BP) regulation.

Methods and Results

We recruited 128 subjects who received annual examinations and 75g-oral glucose tolerance tests (OGTT) in the Tanno-Sobetsu cohort. Subjects on regular medications for cardiovascular and/or metabolic diseases were excluded, and data for the remaining 103 subjects were used for the univariate and multivariate analyses. Age, plasma glucose (PG), hemoglobin A1c (HbA1c), plasma insulin, and serum lipids were not selected as independent determinants of fasting GLP-1 level by multiple linear regression analysis. However, age and female sex were selected as independent positive determinants of the area under the curve of GLP-1 level during OGTT (AUC_GLP-1), an index of GLP-1 secretory function. Multiple linear regression analysis indicated that AUC_GLP-1 was an independent negative predictor of systolic BP (SBP), while AUC_GLP-1 was not correlated with fasting PG or HbA1c level. In subgroup analyses using the median of AUC_GLP-1 to divide the study subjects into high and low GLP-1 response groups, AUC_GLP-1 was significantly correlated with both SBP and diastolic BP (r = 0.40 and 0.28, respectively) in the low GLP-1 response group but not in the high GLP-1 response group.

Conclusions

The results of the present study suggest that GLP-1 secretory function is involved in prevention of BP elevation and that the GLP-1 response to oral glucose rather increases with aging perhaps as an adaptive phenomenon.

New advances in models and strategies for developing anti-obesity drugs

INTRODUCTION

Obesity is a worldwide pandemic. Obesity-related health and economic costs are staggering. Existing strategies to combat obesity through lifestyle improvements and medical intervention have had limited success. Pharmacotherapy, in combination with lifestyle modification, may play a vital role in reversing the disease burden. However, past and current weight-loss medications have had serious safety risks, notably cardiovascular and psychiatric events.

AREAS COVERED

The authors review the strategies for designing new anti-obesity drugs by describing those currently in development. They describe their target, mechanism of action and developmental or regulatory status. Furthermore, they discuss the problem of weight regain following weight loss, and its relevance to the long-term success of anti-obesity pharmacotherapy.

EXPERT OPINION

For weight management drugs to achieve the safety and efficacy required to be impactful, current studies are uncovering and characterizing new targets, including new signaling circuits and hormones regulating appetite and metabolism, and re-evaluating the role of pharmacotherapy in weight management. To avoid the safety failures of many past weight-loss drugs, the models and strategies covered in this article incorporate recent advances in knowledge and technology. We discuss the emergence of cGMP signaling as a potentially transformative target in weight management. Modulating cGMP signaling may represent an ideal goal for an anti-obesity pharmacotherapy, reflecting some of the major themes described in the present review: targeting pathways that are newly realized as relevant for weight management; promoting safety by re-purposing drugs that are safe, proven, and approved for clinical use; and having a synergistic effect on multiple, reinforcing pathways.

Mechanisms of Weight Regain following Weight Loss

Obesity is a world-wide pandemic and its incidence is on the rise along with associated comorbidities. Currently, there are few effective therapies to combat obesity. The use of lifestyle modification therapy, namely, improvements in diet and exercise, is preferable over bariatric surgery or pharmacotherapy due to surgical risks and issues with drug efficacy and safety. Although they are initially successful in producing weight loss, such lifestyle intervention strategies are generally unsuccessful in achieving long-term weight maintenance, with the vast majority of obese patients regaining their lost weight during followup. Recently, various compensatory mechanisms have been elucidated by which the body may oppose new weight loss, and this compensation may result in weight regain back to the obese baseline. The present review summarizes the available evidence on these compensatory mechanisms, with a focus on weight loss-induced changes in energy expenditure, neuroendocrine pathways, nutrient metabolism, and gut physiology. These findings have added a major focus to the field of antiobesity research. In addition to investigating pathways that induce weight loss, the present work also focuses on pathways that may instead prevent weight regain. Such strategies will be necessary for improving long-term weight loss maintenance and outcomes for patients who struggle with obesity.

Biomarker Profile Does Not Predict Weight Loss Success in Successful and Unsuccessful Diet-Reduced Obese Individuals: a Prospective Study

Background. Individuals attempting weight reduction have varying success when participating in the same intervention. Identifying physiological factors associated with greater weight loss could improve outcomes. Methods. Sixty-one adults (BMI 27–30 kg/m²) participated in a 16-week group-based, cognitive-behavioral control weight loss program. Concentrations of 12 fasting hormones and cytokines related to adiposity, satiety/hunger, and inflammation were measured using the Milliplex human metabolic human panel before and after weight loss. Participants were grouped based on ≥8% (successful group, SG) or <8% weight loss (less successful group, LSG). Results. The SG had 46 subjects (75.4%), while the LSG had 15 (24.6%). There were no differences in baseline sex distribution, age, weight, BMI, and body composition between groups. In the SG, baseline to the 16-week levels decreased significantly for c-peptide (1,030 versus 891 pg/mL, P = 0.002), insulin (665 versus 541 pg/mL, P = 0.001), and leptin (0.83 versus 0.58 ng/mL/kg fat, P < 0.001). None of the baseline analytes predicted greater weight loss. Conclusions. Successful weight loss was associated with changes in adiposity (less fat mass) and unfavorable hunger signals. No baseline biomarker profile was associated with weight loss success. Behavioral factors may have outweighed physiological signals for determining successful weight loss. This trial is registered with Clinicaltrials.gov NCT00429650.

Obesity: lessons from evolution and the environment

The 9th Stock Conference acknowledged the complex background of genetic, cultural, environmental and evolutionary factors of obesity. Gene-environment interactions underlie the flexibility in body-weight and body-fat regulation, illustrated by the hunter-gatherers' feast and famine lifestyle, the variation in physical activity over the lifespan being highest at reproductive age, the variation in energy intake through 'eating in the absence of hunger', while running the risk of exceeding the capacity of triacylglyceride storage, leading to lipotoxicity and metabolic problems. Perinatal metabolic programming for obesity via epigenetic changes in response to a 'Western diet' results in production of lipid-poor milk and metabolically efficient pups, contributing to the perpetuation of obesity throughout generations. Evolutionary insight from comparative physiology and ecology indicates that over generations activity-induced energy expenditure has remained the same compared to wild mammals, that energy balance might be dependant on protein balance, while the function of taste changed from detection of poison or energy to social drinking and social behaviour. At present, the impact of assortative mating on obesity prevalence is unambiguously positive. The complexity that appeared can only be fully appreciated by setting the data into the context of our evolutionary history.

The effect of tesofensine on appetite sensations

Tesofensine (TE), an inhibitor of monoamine presynaptic reuptake, has produced twice the weight loss seen with currently marketed drugs. However, its long term effect on appetite in humans has not been studied. A multicentre phase II trial was divided into two parts (24 weeks each). Part 1 had a randomized, double-blind, placebo-controlled design and Part 2, an open-labeled, single-group, uncontrolled design. A drug-free period (12 ± 3 weeks) separated them. In Part 1, participants (n = 158) were assigned to 0.25, 0.5 or 1.0 mg TE, or placebo. Completers of Part 1 were invited to participate in Part 2 (n = 113), during which they all received 0.5 or 1.0 mg TE. Appetite sensations and a composite satiety score (CSS = satiety + fullness + (100 - hunger) + (100 - prospective food consumption) were assessed. In Part 1 TE induced a dose-dependent increase in CSS at week 12 that correlated with weight loss during the 24 weeks (r = 0.36, P < 0.0001). However, CSS diminished over time as weight loss progressed (e.g., for 1.0 mg; 52 ± 17 mm; 64 ± 13 mm; 55 ± 13 mm at baseline, week 12 and week 24, respectively). After drug withdrawal CSS returned to baseline values (50 ± 17 mm, in the whole sample.), despite the participants' reduced-weight state (-7.2 ± 6.7 kg, P < 0.0001). The reintroduction of TE in Part 2 increased CSS again (56 ± 17 mm at week 60), regardless of initial treatment/weight loss. We postulate that enhanced satiety is involved in early weight loss. Whether the attenuated effect on appetite seen after 24 weeks is due to a counteracting effect in the weight reduced state or whether the appetite suppressing effect of TE per se diminishes over time is, however, still unclear.

Advancements in the use of blood tests for cancer screening in women at high risk for endometrial and breast cancer

Several years ago, it was argued that the identification of serum biomarkers is one of the most promising approaches for the detection of early-stage malignant or even premalignant lesions. In this review, the need to establish better monitoring protocols is described for obese women who are at higher risk for the development of malignancies commonly associated with excess weight; specifically endometrial and postmenopausal breast cancer. These cancers have been chosen for this review article as our aim was to focus on female cancers that have been linked with obesity. Cancer screening is essential in detecting disease in its earliest stage in order to reduce morbidity and mortality; however, effective screening is not available for many cancer types. Even for cancers that have effective screening protocols available, there are barriers to screening in obese individuals, such as reduced mobility and embarrassment. These barriers often delay screening in these vulnerable population groups, leading to detection of the disease at a more advanced stage and ultimately leading to a poorer prognosis. As of today, biomarkers do not replace but augment imaging and other existing screening approaches. Future development of blood- or urine-based biomarkers as a way to screen individuals at high risk for certain cancers may prove to be an excellent method for overcoming the barriers that individuals at high risk are facing today. The overall purpose of this manuscript is to provide an overview of screening techniques and to identified barriers and alternate biomarker-based approaches for improvement of endometrial and breast cancer screening in obese women.

Gastric bypass surgery restores meal stimulation of the anorexigenic gut hormones glucagon-like peptide-1 and peptide YY independently of caloric restriction

BACKGROUND

The effects of gastric bypass surgery on the secretion of the anorexigenic gut-derived hormones glucagon-like peptide-1 (GLP-1) and peptide YY (PYY), independent of caloric restriction and due to different dietary macronutrients, is not well characterized. This study examines the effects of a mixed-nutrient or high-fat liquid meal on the postprandial stimulation of GLP-1 and PYY following gastric bypass or equivalent hypocaloric diet.

METHODS

Total PYY and active GLP-1 were measured fasting and at multiple points after standardized mixed-nutrient and high-fat liquid meals in two matched groups of obese subjects. The meal stimulation tests were performed before and 14.6 ± 3.3 days after gastric bypass (GBP, n = 10) and before and after a 7-day hypocaloric liquid diet matching the post-GBP diet (control, n = 10).

RESULTS

Mixed-nutrient and high-fat postprandial GLP-1 levels increased following GBP (mixed-nutrient peak: 85.0 ± 28.6-323 ± 51 pg/ml, P < 0.01; high-fat peak: 81.8 ± 9.6-278 ± 49 pg/ml, P < 0.01), but not after diet (mixed-nutrient peak: 104.4 ± 9.4-114.9 ± 15.8 pg/ml, P = NS; high-fat peak: 118.1 ± 16.4-104.4 ± 10.8 pg/ml, P = NS). The postprandial PYY response also increased after GBP but not diet, though the increase in peak PYY did not reach statistical significance (GBP mixed-nutrient peak: 134.8 ± 26.0-220.7 ± 52.9 pg/ml, P = 0.09; GBP high-fat peak: 142.1 ± 34.6-197.9 ± 12.7 pg/ml, P = 0.07; diet mixed-nutrient peak: 99.8 ± 8.0-101.1 ± 13.3 pg/ml, P = NS; diet high-fat peak: 105.0 ± 8.8-103.1 ± 11.8 pg/ml, P = NS). The postprandial GLP-1 response was not affected by the macronutrient content of the meal. However, following GBP the mixed-nutrient PYY total area under the curve (AUC(0-120)) was significantly greater than the high-fat PYY AUC(0-120) (22,081 ± 5,662 pg/ml min vs. 18,711 ± 1,811 pg/ml min, P = 0.04).

CONCLUSIONS

Following GBP there is an increase in the postprandial stimulation of PYY and GLP-1 that is independent of caloric restriction. The phenomenon of "bariatric surgery-induced anorexia" may be linked to the increased levels after GBP.

The gut hormones PYY 3-36 and GLP-1 7-36 amide reduce food intake and modulate brain activity in appetite centers in humans

Obesity is a major public health issue worldwide. Understanding how the brain controls appetite offers promising inroads toward new therapies for obesity. Peptide YY (PYY) and glucagon-like peptide 1 (GLP-1) are coreleased postprandially and reduce appetite and inhibit food intake when administered to humans. However, the effects of GLP-1 and the ways in which PYY and GLP-1 act together to modulate brain activity in humans are unknown. Here, we have used functional MRI to determine these effects in healthy, normal-weight human subjects and compared them to those seen physiologically following a meal. We provide a demonstration that the combined administration of PYY(3-36) and GLP-1(7-36 amide) to fasted human subjects leads to similar reductions in subsequent energy intake and brain activity, as observed physiologically following feeding.