Effect of anorexic drugs on food intake and the micro-structure of eating in human subjects

Exposure to Instagram junk food content negatively impacts mood and cravings in young adults: A randomized controlled trial

Exposure to different types of images on social media is known to affect physical and mental wellbeing including changes in perception of body image (BI) and dietary behavior. The present study aimed to assess the effects of junk food-related Instagram content exposure on body image, overall mood, and cravings in young adults. A randomized crossover experimental design was used. After filling out a baseline survey, participants (n = 63, aged 18-24) browsed either a control Instagram account feed or an account rich in junk food images during 15 min. They then filled a short survey evaluating their state BI, mood, and cravings (T1). After a 1-week washout period (T2), participants browsed the other account type followed by the same short survey as in T1. Results showed that exposure to junk food content was associated with increased feelings of hunger, stress, sadness, and exhaustion, in addition to higher salty, savory, and fatty food cravings. Moreover, participants showed higher desire for junk food and lower desire for healthy food items from a virtual food tray after junk food content exposure. There was no impact of content type on state BI dissatisfaction. In conclusion, exposure to junk-food related content on social media negatively affects mood and cravings, subsequently influencing food choices. The present findings shed light on the need for interventions aimed at providing cognitive and emotional competencies for enhancing media literacy and promoting mindful social media use.

Orthonasal olfactory influences on consumer food behaviour

It is often suggested in the popular press that food chains deliberately introduce enticing product aromas into (and in the immediate vicinity of) their premises in order to attract customers. However, despite the widespread use of odours in the field of sensory marketing, laboratory research suggests that their effectiveness in modulating people's food behaviours depends on a range of contextual factors. Given the evidence that has been published to date, only under a subset of conditions is there likely to be a measurable effect of the presence of ambient odours on people's food attitudes and choices. This narrative historical review summarizes the various ways in which food odours appear to bias people's food preferences (appetite) and food choices (food consumption and purchase). Emphasis is placed on those experimental studies that have been designed to investigate how the characteristics of the olfactory stimuli (e.g., the congruency between the olfactory cues and the foods, intensity and duration of exposure to odours, and taste properties of odours) modulate the effects of olfactory cues on food behaviour. The review also explores the moderating roles of individual differences, such as dietary restraint, Body Mass Index (BMI), genetic and cultural differences in odour sensitivity and perception. Ultimately, following a review of empirical studies on food-related olfaction, current approaches in scent marketing are discussed and a research agenda is proposed to help encourage further studies on the effective application of scents in promoting healthy foods.

Cross-linked phosphorylated RS4 wheat starch reduces glucose and insulin responses after 3 days of pre-feeding in healthy adults: an acute, double-blind, randomized controlled clinical trial

When this project was designed, there was no evidence that adding resistant starch to available carbohydrate (avCHO) reduced glycaemic and insulinaemic responses (GIR). We compared GIR elicited by a cookie containing cross-linked phosphorylated RS4 wheat starch (Fibersym®) (RS4XL) versus an avCHO-matched control-cookie (CC) after n = 15 adults had consumed RS4XL or CC daily for 3-days using a double-blind, randomised, cross-over design. The difference in glucose iAUC over 0-2 h (primary endpoint) (mmol × min/L) after RS4XL, (mean ± SEM) 106 ± 16, versus CC, 124 ± 16, was not significant (p = 0.087). However, RS4XL reduced 0-90 min glucose iAUC (72 ± 9 vs 87 ± 9, p = 0.022), peak glucose concentration (6.05 ± 0.36 vs 6.57 ± 0.31 mmol/L, p = 0.017) and 0-2 h insulin iAUC (189 ± 21 vs 246 ± 24 nmol × h/L, p = 0.020). These results show that RS4XL reduced postprandial glycaemic and insulinaemic responses when added to avCHO, but do not prove that the products of its colonic fermentation are required for this effect.

Unraveling the serotonin saga: from discovery to weight regulation and beyond - a comprehensive scientific review

The prevalence of obesity is rapidly increasing worldwide, while the development of effective obesity therapies lags behind. Although new therapeutic targets to alleviate obesity are identified every day, and drug efficacy is improving, adverse side effects and increased health risks remain serious issues facing the weight-loss industry. Serotonin, also known as 5-HT, has been extensively studied in relation to appetite reduction and weight loss. As a result, dozens of upstream and downstream neural targets of 5-HT have been identified, revealing a multitude of neural circuits involved in mediating the anorexigenic effect of 5-HT. Despite the rise and fall of several 5-HT therapeutics in recent decades, the future of 5-HT as a therapeutic target for weight-loss therapy looks promising. This review focuses on the history of serotonin, the state of current central serotonin research, previous serotonergic therapies, and the future of serotonin for treating individuals with obesity.

SenseHunger: Machine Learning Approach to Hunger Detection Using Wearable Sensors

The perception of hunger and satiety is of great importance to maintaining a healthy body weight and avoiding chronic diseases such as obesity, underweight, or deficiency syndromes due to malnutrition. There are a number of disease patterns, characterized by a chronic loss of this perception. To our best knowledge, hunger and satiety cannot be classified using non-invasive measurements. Aiming to develop an objective classification system, this paper presents a multimodal sensory system using associated signal processing and pattern recognition methods for hunger and satiety detection based on non-invasive monitoring. We used an Empatica E4 smartwatch, a RespiBan wearable device, and JINS MEME smart glasses to capture physiological signals from five healthy normal weight subjects inactively sitting on a chair in a state of hunger and satiety. After pre-processing the signals, we compared different feature extraction approaches, either based on manual feature engineering or deep feature learning. Comparative experiments were carried out to determine the most appropriate sensor channel, device, and classifier to reliably discriminate between hunger and satiety states. Our experiments showed that the most discriminative features come from three specific sensor modalities: Electrodermal Activity (EDA), infrared Thermopile (Tmp), and Blood Volume Pulse (BVP).

5-HT recruits distinct neurocircuits to inhibit hunger-driven and non-hunger-driven feeding

Obesity is primarily a consequence of consuming calories beyond energetic requirements, but underpinning drivers have not been fully defined. 5-Hydroxytryptamine (5-HT) neurons in the dorsal Raphe nucleus (5-HTDRN) regulate different types of feeding behavior, such as eating to cope with hunger or for pleasure. Here, we observed that activation of 5-HTDRN to hypothalamic arcuate nucleus (5-HTDRN → ARH) projections inhibits food intake driven by hunger via actions at ARH 5-HT2C and 5-HT1B receptors, whereas activation of 5-HTDRN to ventral tegmental area (5-HTDRN → VTA) projections inhibits non-hunger-driven feeding via actions at 5-HT2C receptors. Further, hunger-driven feeding gradually activates ARH-projecting 5-HTDRN neurons via inhibiting their responsiveness to inhibitory GABAergic inputs; non-hunger-driven feeding activates VTA-projecting 5-HTDRN neurons through reducing a potassium outward current. Thus, our results support a model whereby parallel circuits modulate feeding behavior either in response to hunger or to hunger-independent cues.

TPH2 in the Dorsal Raphe Nuclei Regulates Energy Balance in a Sex-Dependent Manner

AbstractCentral 5-hydroxytryptamine (5-HT), which is primarily synthesized by tryptophan hydroxylase 2 (TPH2) in the dorsal Raphe nuclei (DRN), plays a pivotal role in the regulation of food intake and body weight. However, the physiological functions of TPH2 on energy balance have not been consistently demonstrated. Here we systematically investigated the effects of TPH2 on energy homeostasis in adult male and female mice. We found that the DRN harbors a similar amount of TPH2+ cells in control male and female mice. Adult-onset TPH2 deletion in the DRN promotes hyperphagia and body weight gain only in male mice, but not in female mice. Ablation of TPH2 reduces hypothalamic pro-opiomelanocortin (POMC) neuronal activity robustly in males, but only to a modest degree in females. Deprivation of estrogen by ovariectomy (OVX) causes comparable food intake and weight gain in female control and DRN-specific TPH2 knockout mice. Nevertheless, disruption of TPH2 blunts the anorexigenic effects of exogenous estradiol (E2) and abolishes E2-induced activation of POMC neurons in OVX female mice, indicating that TPH2 is indispensable for E2 to activate POMC neurons and to suppress appetite. Together, our study revealed that TPH2 in the DRN contributes to energy balance regulation in a sexually dimorphic manner.

Increasing oat β-glucan viscosity in a breakfast meal slows gastric emptying and reduces glycemic and insulinemic responses but has no effect on appetite, food intake, or plasma ghrelin and PYY responses in healthy humans: a randomized, placebo-controlled, crossover trial

BACKGROUND

The viscosity of oat β-glucan (OBG) determines its effect on serum cholesterol and glycemic responses, but whether OBG viscosity affects gastric emptying, appetite, and ad libitum food intake is unknown.

OBJECTIVES

We aimed to determine the effect of altering the amount or molecular weight (MW) and, hence, viscosity of OBG in a breakfast meal on the primary endpoint of food intake at a subsequent meal.

METHODS

Overnight-fasted males (n = 16) and nonpregnant females (n = 12) without diabetes, aged 18-60 y, with BMI 20.0-30.0 kg/m² who were unrestrained eaters participated in a double-blind, randomized, crossover study at a contract research organization. Participants consumed, in random order, breakfast meals equivalent in weight, energy, and macronutrients consisting of white-bread, butter, jam, and 2% milk plus hot cereal [Cream of Rice (CR), or instant-oatmeal plus either 3 g oat-bran (2gOBG), 10 g oat-bran (4gOBG), or 10 g oat-bran plus β-glucanase (4gloMW) to reduce OBG MW and viscosity compared with 4gOBG]. Gastric emptying, subjective appetite, and glucose, insulin, ghrelin, and peptide tyrosine tyrosine (PYY) responses were assessed for 3 h and then subjects were offered an ad libitum lunch (water and pizza).

RESULTS

Pizza intakes (n = 28) after CR, 2gOBG, 4gOBG, and 4gloMW (mean ± SEM: 887 ± 64, 831 ± 61, 834 ± 78, and 847 ± 68 kcal, respectively) were similar (nonsignificant). Compared with CR, 4gOBG significantly reduced glucose (78 ± 10 compared with 135 ± 15 mmol × min/L) and insulin (14.0 ± 1.6 compared with 26.8 ± 3.5 nmol × min/L) incremental area-under-the-curve and delayed gastric-emptying half-time (geometric mean: 285; 95% CI: 184, 442, compared with geometric mean: 105; 95% CI: 95, 117 min), effects not seen after 4gloMW. Subjective appetite, PYY, and ghrelin responses after 2gOBG, 4gOBG, and 4gloMW were similar to those after CR.

CONCLUSIONS

The results demonstrate that OBG viscosity determines its effect on postprandial glucose, insulin, and gastric emptying. However, we were unable to demonstrate a significant effect of OBG on appetite or food intake, regardless of its viscosity.This trial was registered at clinicaltrials.gov as NCT03490851.

Profiles of peptide YY and ghrelin, levels of hunger and satiety, and ad libitum intake in obese and non-obese Indonesian women

INTRODUCTION

The current study aimed to assess profiles of peptide YY and ghrelin, visual analog scales (VAS) for hunger and satiety, and ad libitum intake in obese and non-obese women.

METHODS

This open-label non-randomized interventional study involved obese (BMI ≥ 25-35 kg/m2) and non-obese (BMI 18.5-23.0 kg/m2) women subjects. Levels of peptide YY and ghrelin were determined by radioimmunoassay and enzyme-linked immunosorbent assay (ELISA), respectively, while the degrees of hunger and satiety were measured using visual analog scale (VAS) questionnaires. The results were compared in fasting condition and in 15, 60, 120, and 180 minutes after breakfast with balance composition formulation. This study also compared the ad libitum intake within 4 hours after breakfast.

RESULTS

As compared to the non-obese group, the obese group have significantly lower levels of peptide YY in fasting, and in 15, 60, 120, and 180 minutes post-prandial, and smaller AUC (Area Under the Curve) of fasting peptide YY. Furthermore, the obese group showed significantly higher ad libitum intake. The obese group also have lower levels of ghrelin and lower VAS for hunger and higher in VAS for satiety as compared to the non-obese group.

CONCLUSIONS

There were significant differences in peptide YY level, 4 hours after breakfast ad libitum intake, ghrelin level, and VAS for hunger and satiety, between obese group and non-obese one.

Central regulation of energy metabolism by estrogens

BACKGROUND

Estrogenic actions in the brain prevent obesity. Better understanding of the underlying mechanisms may facilitate development of new obesity therapies.

SCOPE OF REVIEW

This review focuses on the critical brain regions that mediate effects of estrogens on food intake and/or energy expenditure, the molecular signals that are involved, and the functional interactions between brain estrogens and other signals modulating metabolism. Body weight regulation by estrogens in male brains will also be discussed.

MAJOR CONCLUSIONS

17β-estradiol acts in the brain to regulate energy homeostasis in both sexes. It can inhibit feeding and stimulate brown adipose tissue thermogenesis. A better understanding of the central actions of 17β-estradiol on energy balance would provide new insight for the development of therapies against obesity in both sexes.

Accumulating Data to Optimally Predict Obesity Treatment (ADOPT) Core Measures: Psychosocial Domain

BACKGROUND

Within the Accumulating Data to Optimally Predict obesity Treatment (ADOPT) Core Measures Project, the psychosocial domain addresses how psychosocial processes underlie the influence of obesity treatment strategies on weight loss and weight maintenance. The subgroup for the psychosocial domain identified an initial list of high-priority constructs and measures that ranged from relatively stable characteristics about the person (cognitive function, personality) to dynamic characteristics that may change over time (motivation, affect).

OBJECTIVES

This paper describes (a) how the psychosocial domain fits into the broader model of weight loss and weight maintenance as conceptualized by ADOPT; (b) the guiding principles used to select constructs and measures for recommendation; (c) the high-priority constructs recommended for inclusion; (d) domain-specific issues for advancing the science; and (e) recommendations for future research.

SIGNIFICANCE

The inclusion of similar measures across trials will help to better identify how psychosocial factors mediate and moderate the weight loss and weight maintenance process, facilitate research into dynamic interactions with factors in the other ADOPT domains, and ultimately improve the design and delivery of effective interventions.

Feed-forward neural network model for hunger and satiety related VAS score prediction

BACKGROUND

An artificial neural network approach was chosen to model the outcome of the complex signaling pathways in the gastro-intestinal tract and other peripheral organs that eventually produce the satiety feeling in the brain upon feeding.

METHODS

A multilayer feed-forward neural network was trained with sets of experimental data relating concentration-time courses of plasma satiety hormones to Visual Analog Scales (VAS) scores. The network successfully predicted VAS responses from sets of satiety hormone data obtained in experiments using different food compositions.

RESULTS

The correlation coefficients for the predicted VAS responses for test sets having i) a full set of three satiety hormones, ii) a set of only two satiety hormones, and iii) a set of only one satiety hormone were 0.96, 0.96, and 0.89, respectively. The predicted VAS responses discriminated the satiety effects of high satiating food types from less satiating food types both in orally fed and ileal infused forms.

CONCLUSIONS

From this application of artificial neural networks, one may conclude that neural network models are very suitable to describe situations where behavior is complex and incompletely understood. However, training data sets that fit the experimental conditions need to be available.

β-glucans: ex vivo inflammatory and oxidative stress results after pasta intake

BACKGROUND

It is well known that Mediterranean Diet can positively influence the health of each individual, in particular it is know that fibers have an important role. However, in Mediterranean cities most people do not have a close adherence to Mediterranean diet. Thus, in our study, we considered fibers like β-glucans that have been added to pasta with a percentage of 6 %. Our study aimed to evaluate the capacity of β-glucans intake on oxidative stress and inflammation in a cohort of middle aged slightly overweight subjects.

METHODS

We used a longitudinal study design. The study lasted 30 days during which time, each participant acted with no food restriction. Participants underwent morning fasting blood venous sample for blood chemistry and other biological parameters at the beginning of the study and after 30 days of pasta supplemented with 6 % of β-glucan intake 4 times a week. We performed anthropometric, biochemical, oxidative stress and cytokine analysis at the beginning and the end of study.

RESULTS

After the 30 days of pasta intake we obtained a significant decrease of LDL-cholesterol, IL-6 and AGEs levels.

CONCLUSION

The results confirmed a capacity of β-glucans intake to lower oxidative stress. Additional longitudinal observation on community-based cohorts are needed to confirm these data and investigate the biological mechanisms through which effects are induced, and to fully explore the therapeutic potential of β-glucans.

Dietary fiber and satiety: the effects of oats on satiety

This review examines the effect of β-glucan, the viscous soluble fiber in oats, on satiety. A literature search for studies that examined delivery of the fiber in whole foods or as an extract was conducted. Viscosity interferes with the peristaltic mixing process in the small intestine to impede digestion and absorption of nutrients, which precipitates satiety signals. From measurements of the physicochemical and rheological properties of β-glucan, it appears that viscosity plays a key role in modulating satiety. However, the lack of standardized methods to measure viscosity and the inherent nature of appetite make it difficult to pinpoint the reasons for inconsistent results of the effects of oats on satiety. Nevertheless, the majority of the evidence suggests that oat β-glucan has a positive effect on perceptions of satiety.

Food reward. What it is and how to measure it

We investigated the contribution of hunger and food liking to food reward, and the relationship between food reward and food intake. We defined liking as the pleasantness of taste of food in the mouth, and food reward as the momentary value of a food to the individual at the time of ingestion. Liking and food reward were measured, respectively, by ratings of the pleasantness of the taste of a mouthful, and ratings of desire to eat a portion, of the food in question. Hunger, which we view as primarily the absence of fullness, was rated without food being present. Study 1 provided evidence that hunger and liking contribute independently to food reward, with little effect of hunger on liking. Food intake reduced liking and reward value more for the eaten food than uneaten foods. The results were ambiguous as to whether this food-specific decline in reward value ('sensory-specific satiety') involved a decrease in 'wanting' in addition to the decrease in liking. Studies 2 and 3 compared desire to eat ratings with work-for-food and pay-for-food measures of food reward, and found desire to eat to be equal or superior in respect of effects of hunger and liking, and superior in predicting ad libitum food intake. A further general observation was that in making ratings of food liking participants may confuse the pleasantness of the taste of food with the pleasantness of eating it. The latter, which some call 'palatability,' decreases more with eating because it is significantly affected by hunger/fullness. Together, our results demonstrate the validity of ratings of desire to eat a portion of a tasted food as a measure of food reward and as a predictor of food intake.

Metabolic Phenotyping Guidelines: studying eating behaviour in humans

The study of human appetite and eating behaviour has become increasingly important in recent years due to the rise in body weight dysregulation through both obesity and eating disorders. Adequate control over appetite is paramount for the control of body weight and in order to understand appetite, it is necessary to measure eating behaviour accurately. So far, research in this field has revealed that no single experimental design can answer all research questions. Each research question posed will require a specific study design that will limit the findings of that study to those particular conditions. For example, choices will be made among the use of laboratory or free-living studies, time period for examination, specific measurement techniques and investigative methodologies employed. It is important that these represent informed decisions about what design and which methodology will provide the most meaningful outcomes. This review will examine some of the 'gold standard' study designs and methodologies currently employed in the study of human appetite and eating behaviour.

Appetite sensations, appetite signaling proteins, and glucose in obese adolescents with subclinical binge eating disorder

Objective. This study aimed to investigate potential differences in appetite sensations, ghrelin, peptide YY, and glucose and their relationship with energy and macronutrient intake in obese adolescents with subclinical binge eating disorder. Methods. Fifteen obese adolescents (six and nine individuals with and without subclinical binge eating disorder, resp.) qualified for this study. Visual analog scales and Three-Factor Eating Questionnaires were used to assess eating behaviours. Circulating ghrelin, peptide YY, and glucose were measured after fasting and at multiple time points postprandially following a standardized breakfast meal. Energy and macronutrient intake were measured with an ad libitum lunch buffet. Results. Emotional eating scores were significantly higher in obese adolescents with subclinical binge eating disorder. Hunger levels rose and satiety levels fell significantly over the course of the monitoring period but there was no difference between the two groups. Obese adolescents with subclinical binge eating disorder did not have significantly different levels of appetite signaling proteins or glucose. Obese adolescents with subclinical binge eating disorder had a nonsignificantly higher energy and macronutrient intake. Conclusions. A significant difference between the two groups in terms of their emotional eating scores highlights the important role that psychological factors play in relation to eating behaviours.

Satiety, but not total PYY, Is increased with continuous and intermittent exercise

OBJECTIVE

This study determined the hormonal and subjective appetite responses to exercise (1-h continuous versus intermittent exercise throughout the day) in obese individuals.

DESIGN AND METHODS

Eleven obese subjects (>30 kg/m(2) ) underwent three 12-h study days: control condition [sedentary behavior (SED)], continuous exercise condition [(EX) 1-h exercise], and intermittent exercise condition [(INT) 12 hourly, 5-min bouts]. Blood samples (every 10 min) were measured for serum insulin and total peptide YY (PYY) concentrations, with ratings of appetite (visual analog scale [VAS): every 20 min]. Both total area under the curve (AUC), and subjective appetite ratings were calculated.

RESULTS

No differences were observed in total PYY AUC between conditions, but hunger was reduced with INT (INT < EX; P < 0.05), and satiety was increased with both SED and INT conditions (INT > EX and SED > EX; P < 0.05). A correlation existed between the change in total PYY and insulin levels (r = -0.81; P < 0.05), and total PYY and satiety (r = 0.80; P < 0.05) with the EX condition, not the SED and INT conditions.

CONCLUSIONS

The total PYY response to meals is not altered over the course of a 12-h day with either intermittent or continuous exercise; however, intermittent exercise increased satiety and reduced hunger to a greater extent than continuous exercise in obese individuals.

Serotonin and the regulation of mammalian energy balance

Maintenance of energy balance requires regulation of the amount and timing of food intake. Decades of experiments utilizing pharmacological and later genetic manipulations have demonstrated the importance of serotonin signaling in this regulation. Much progress has been made in recent years in understanding how central nervous system (CNS) serotonin systems acting through a diverse array of serotonin receptors impact feeding behavior and metabolism. Particular attention has been paid to mechanisms through which serotonin impacts energy balance pathways within the hypothalamus. How upstream factors relevant to energy balance regulate the release of hypothalamic serotonin is less clear, but work addressing this issue is underway. Generally, investigation into the central serotonergic regulation of energy balance has had a predominantly “hypothalamocentric” focus, yet non-hypothalamic structures that have been implicated in energy balance regulation also receive serotonergic innervation and express multiple subtypes of serotonin receptors. Moreover, there is a growing appreciation of the diverse mechanisms through which peripheral serotonin impacts energy balance regulation. Clearly, the serotonergic regulation of energy balance is a field characterized by both rapid advances and by an extensive and diverse set of central and peripheral mechanisms yet to be delineated.

Unraveling the mechanisms responsible for the comorbidity between metabolic syndrome and mental health disorders

The increased prevalence and high comorbidity of metabolic syndrome (MetS) and mental health disorders (MHDs) have prompted investigation into the potential contributing mechanisms. There is a bidirectional association between MetS and MHDs including schizophrenia, bipolar disorder, depression, anxiety, attention-deficit/hyperactivity disorder, and autism spectrum disorders. Medication side effects and social repercussions are contributing environmental factors, but there are a number of shared underlying neurological and physiological mechanisms that explain the high comorbidity between these two disorders. Inflammation is a state shared by both disorders, and it contributes to disruptions of neuroregulatory systems (including the serotonergic, dopaminergic, and neuropeptide Y systems) as well as dysregulation of the hypothalamic-pituitary-adrenal axis. MetS in pregnant women also exposes the developing fetal brain to inflammatory factors that predispose the offspring to MetS and psychopathologies. Due to the shared nature of these conditions, treatment should address aspects of both mental health and metabolic disorders. Additionally, interventions that can interrupt the transfer of increased risk of the disorders to the next generation need to be developed. © 2013 S. Karger AG, Basel.

Serotonergic anti-obesity agents: past experience and future prospects

The role of serotonin (5-hydroxytryptamine) in appetite control is long established. Serotonergic manipulations reduce food intake in rodents in a manner consistent with satiety. In humans, drugs such as fenfluramine, dexfenfluramine and sibutramine all reduce energy intake, suppress hunger and enhance satiety. Effects on eating behaviour and subjective sensations of appetite are associated with the weight loss-inducing effects of these treatments. Currently, no appetite-suppressing drugs are approved specifically for the treatment of obesity. However, a new generation of serotonergic drugs have progressed through clinical development. The serotonin 5-HT(2C)-receptor selective agonist lorcaserin, a drug specifically developed to target satiety without producing the side effect profiles of its predecessors, has been shown to significantly reduce energy intake and body weight. The weight loss produced by lorcaserin appears modest, and behavioural effects, particularly its supposed satiety-enhancing effects, have yet to be characterized. The monoaminergic re-uptake inhibitor tesofensine has also been shown to produce impressive weight loss in smaller-scale clinical studies. It remains unclear if this drug produces any effects on appetite mediated by serotonin, or whether weight loss is produced largely through enhanced energy expenditure. Evidence indicates that tesofensine strengthens satiety, but behavioural specificity and psychological side effects remain an issue. The serotonergic system remains a viable target for anti-obesity treatment. In this review, we examine the limited behavioural data available on these two new CNS-acting appetite suppressants.

Satiety-enhancing products for appetite control: science and regulation of functional foods for weight management

The current review considers satiety-based approaches to weight management in the context of health claims. Health benefits, defined as beneficial physiological effects, are what the European Food Safety Authority bases their recommendations on for claim approval. The literature demonstrates that foods that target within-meal satiation and post-meal satiety provide a plausible approach to weight management. However, few ingredient types tested produce the sustainable and enduring effects on appetite accompanied by the necessary reductions in energy intake required to claim satiety/reduction in hunger as a health benefit. Proteins, fibre types, novel oils and carbohydrates resistant to digestion all have the potential to produce beneficial short-term changes in appetite (proof-of-concept). The challenge remains to demonstrate their enduring effects on appetite and energy intake, as well as the health and consumer benefits such effects provide in terms of optimising successful weight management. Currently, the benefits of satiety-enhancing ingredients to both consumers and their health are under researched. It is possible that such ingredients help consumers gain control over their eating behaviour and may also help reduce the negative psychological impact of dieting and the physiological consequences of energy restriction that ultimately undermine weight management. In conclusion, industry needs to demonstrate that a satiety-based approach to weight management, based on single-manipulated food items, is sufficient to help consumers resist the situational and personal factors that drive overconsumption. Nonetheless, we possess the methodological tools, which when employed in appropriate designs, are sufficient to support health claims.

5-HT(2C) receptor agonists and the control of appetite

The role of serotonin (5-HT) in appetite control is well recognised. 5-HT drugs reduce food intake in rodents in a manner consistent with an enhancement of satiety. In humans, they have been shown to reduce caloric intake, an effect associated with reduced hunger and increased satiety. These effects appear to be mediated, at least in part, by the 5-HT(2C) receptor subtype. 5-HT-acting drugs such as fenfluramine, d-fenfluramine, and sibutramine have provided effective anti-obesity treatments in the past. However, more selective agents are needed that produce the same changes in eating behaviour and induce weight loss without unacceptable side effects. Lorcaserin, a selective 5-HT(2C) receptor agonist, is a novel anti-obesity agent that reduces both energy intake and body weight. The effects of lorcaserin on eating behaviour remain to be characterised as does its behavioural specificity.

Both longer oral sensory exposure to and higher intensity of saltiness decrease ad libitum food intake in healthy normal-weight men

Orosensory exposure to sweetness has been shown to be important in satiation, whereas the effect of exposure to a salty taste on satiation is not known. The primary objective was to investigate the effect of orosensory exposure time to and intensity of saltiness in soup on ad libitum intake. The secondary objective was to investigate the effect of intensity on bite size. Fifty-five healthy men consumed ad libitum from both a low-salt (LS) and a high-salt (HS) creamy tomato soup in 2 exposure time conditions ("long" and "short") and a free condition ("free"). Bites were administered and controlled via a pump. In the long condition, bites of 5 g were administered in 2 s at intervals of 5 s (exposure time: 24 s/min). In the short condition, bites of 15 g were administered in 3 s at intervals of 15 s (exposure time: 12 s/min). The eating rate was equal in the long and short conditions (60 g/min). In the free condition, participants adjusted their bite sizes at intervals of 15 s. The short condition resulted in ~34% higher ad libitum intake compared to the long condition (P < 0.001); there was no interaction with intensity. Ad libitum intake of HS soup was ~9% lower than LS soup (P < 0.001). The free condition showed that HS soup was consumed with smaller bite sizes during the first half of the intake period (P < 0.05). Longer orosensory exposure and higher saltiness intensity both decreased food intake, although orosensory exposure had more impact than intensity. Prolonging the orosensory exposure per food unit may be helpful to reduce food intake.

Central nervous control of energy and glucose balance: focus on the central melanocortin system

Studies have suggested that manipulations of the central melanocortin circuitry by pharmacological agents produce robust effects on the regulation of body weight and glucose homeostasis. In this review, we discuss recent findings from genetic mouse models that have further established the physiological relevance of this circuitry in the context of glucose and energy balance. In addition, we will discuss distinct neuronal populations that respond to central melanocortins to regulate food intake, energy expenditure, insulin sensitivity, and insulin secretion, respectively. Finally, multiple hormonal and neural cues (e.g., leptin, estrogen, and serotonin) that use the melanocortin systems to regulate energy and glucose homeostasis will be reviewed. These findings suggest that targeting the specific branches of melanocortin circuits may be potential avenues to combat the current obesity and diabetes epidemics.

Medications for weight reduction

Comparatively few drugs are available for the treatment of overweight patients, and their effectiveness is limited to palliation of the chronic disease of obesity. Nevertheless, drug development that is now underway is more rapid than in the past, and we anticipate the discovery of safe and effective pharmacologic strategies for the management of obesity and its serious complications.

Lorcaserin for the treatment of obesity

Obesity is a worldwide epidemic and there is an urgent need for the development of effective pharmacological therapies that target the metabolic and behavioral factors of body weight regulation. Serotonin (5-HT) has been implicated as a critical factor in the short-term (meal-by-meal) regulation of food intake and pharmaceutical companies have invested millions of dollars to discover and develop drug targets for the serotonergic pathway. Lorcaserin is a novel selective agonist of the 5-HT(2C) receptor for weight loss therapy. Preclinical and clinical studies indicate lorcaserin is well tolerated and not associated with cardiac valvulopathy or pulmonary hypertension suggesting that lorcaserin is a selective 5-HT(2C) receptor agonist and has little or no activation of the 5-HT(2B) and 5-HT(2A) receptors, respectively. Lorcaserin acts to alter energy balance through a reduction in energy intake and without an increase in energy expenditure and achieved the U.S. Food and Drug Administration guidelines for weight loss efficacy. It remains to be determined whether or not lorcaserin will be approved for the long-term management of obesity.

Effects of food form on food intake and postprandial appetite sensations, glucose and endocrine responses, and energy expenditure in resistance trained v. sedentary older adults

Limited research has suggested that the food form of nutritional supplements (FFNS) and resistance training (RT) influence ingestive behaviour and energy balance in older adults. The effects of the FFNS and RT on acute appetitive, endocrine and metabolic responses are not adequately documented. The present study assessed the effects of the FFNS and RT on postprandial appetite sensations (hunger and fullness), endocrine responses (plasma insulin, cholecystokinin, ghrelin and glucagon-like peptide-1 (GLP-1)), metabolism (glucose, energy expenditure and RER) and food intake (satiation) in older adults. On separate days, eighteen sedentary (Sed) and sixteen RT healthy adults (age 62-84 years) consumed 12·5 % of their energy need as an isoenergetic- and macronutrient-matched solid or beverage. Postprandial responses were assessed over 4 h. No RT × FFNS interactions were observed for any parameter. Fasting cholecystokinin was higher in the RT v. Sed group (P < 0·05). RT did not influence fullness, but fullness was higher following the solid v. beverage intake (P < 0·01). Neither RT nor FFNS influenced hunger. Glucose and insulin were higher after the solid v. beverage intake (P < 0·01). Ghrelin, GLP-1 and energy expenditure were not different between the RT and FFNS groups. Postprandial cholecystokinin was higher in the RT v. Sed group (P < 0·01) and for solid v. beverage (P < 0·05). RER was lower for solid v. beverage (P < 0·001). Neither RT nor FFNS independently or interactively influenced food intake 2 h after post-nutritional supplements. In conclusion, RT had little influence on ingestive behaviour. The appetitive and endocrine responses suggested the solid-promoted satiety; however, the FFNS did not alter subsequent food intake.

The use of serotonergic drugs to treat obesity--is there any hope?

Surgical interventional strategies for the treatment of obesity are being implemented at an increasing rate. The safety and feasibility of these procedures are questionable for most overweight or obese individuals. The use of long-term pharmacotherapy options, on the other hand, can target a greater portion of the obese population and provide early intervention to help individuals maintain a healthy lifestyle to promote weight loss. Medications that act on the central serotonergic pathways have been a relative mainstay for the treatment of obesity for the last 35 years. The clinical efficacy of these drugs, however, has been encumbered by the potential for drug-associated complications. Two drugs that act, albeit by different mechanisms, on the central serotonergic system to reduce food intake and decrease body weight are sibutramine and lorcaserin. Sibutramine is a serotonin and norepinephrine reuptake inhibitor, whereas lorcaserin is a selective 5HT_2C receptor agonist. The recent worldwide withdrawal of sibutramine and FDA rejection of lorcaserin has changed the landscape not only for serotonin-based therapeutics specifically, but for obesity pharmacotherapy in general. The purpose of this review is to focus on the importance of the serotonergic system in the control of feeding and its potential as a target for obesity pharmacotherapy. Advances in refining and screening more selective receptor agonists and a better understanding of the potential off-target effects of serotonergic drugs are needed to produce beneficial pharmacotherapy.

Pharmacological management of appetite expression in obesity

For obese individuals, successful weight loss and maintenance are notoriously difficult. Traditional drug development fails to exploit knowledge of the psychological factors that crucially influence appetite, concentrating instead on restrictive criteria of intake and weight reduction, allied to a mechanistic view of energy regulation. Drugs are under development that may produce beneficial changes in appetite expression in the obese. These currently include glucagon-like peptide-1 analogs such as liraglutide, an amylin analog davalintide, the 5-HT(2C) receptor agonist lorcaserin, the monoamine re-uptake inhibitor tesofensine, and a number of combination therapies such as pramlintide and metreleptin, bupropion and naltrexone, phentermine and topiramate, and bupropion and zonisamide. However, the effects of these treatments on eating behavior remain poorly characterized. Obesity is typically a consequence of overconsumption driven by an individual's natural sensitivity to food stimuli and the pleasure derived from eating. Intuitively, these processes should be effective targets for pharmacotherapy, and behavioral analysis can identify drugs that selectively affect desire to eat, enjoyment of eating, satiation or postmeal satiety. Rational interventions designed specifically to modulate these processes could limit the normally aversive consequences of caloric restriction and maximize an individual's capacity to successfully gain control over their appetite.

Hunger and thirst: issues in measurement and prediction of eating and drinking

Associations between hunger and eating and between thirst and drinking are generally weak. This stems, in part, from limitations in the measurement of these sensations which generally rely on temporal, motivational, metabolic and/or self-reported descriptive indices. Each is critically reviewed. Also problematic is the fact that the deterministic depletion-repletion concept of ingestive behavior fails to account for influences of a multitude of contravening cognitive, social, sensory and logistical factors. Although hunger and thirst serve some parallel purposes, sharp distinctions are also present with health implications. Of particular note are the observations that thirst ratings are higher and more stable over the day compared to hunger and thirst may be more motivating to drink than hunger is to eat. Coupling these observations with evidence that beverages have limited satiety value, they pose particular challenges and opportunities. Beverages can facilitate the delivery of nutrients to those desiring or requiring them, but also to those where they are not desired or required. The benefits and risks are a function of their use rather than their inherent properties.

The effects of sibutramine on the microstructure of eating behaviour and energy expenditure in obese women

Given the suggestion that many potential anti-obesity drugs may enhance within-meal satiation, few studies have directly measured the effects of any drug on the microstructure of human eating behaviour. The effects of 7 days dosing with sibutramine 10 mg and 15 mg a day on appetite and energy balance were determined in 30 obese women (BMI 34.6 +/- 3.3 kg/m2, age 46.0 +/- 12.9 years) using a Universal Eating Monitor (UEM) and indirect calorimetry, in a double-blind, placebo-controlled crossover study. At day 7, sibutramine 10 mg and 15 mg reduced food intake by 16.6% and 22.3%, respectively (p < 0.001), compared with placebo. Sibutramine reduced eating rate compared with placebo rather than meal length (10 mg p < 0.05; 15 mg p < 0.001). In addition, sibutramine 10 mg significantly reduced hunger later in the meal (p < 0.05) and sibutramine 15 mg increased fullness early in the meal (p < 0.01), both of which are consistent with enhanced within-meal satiation. Sibutramine had little effect on resting metabolic rate, although 15 mg did significantly reduce respiratory quotient at several time points during the test day. These results provide novel evidence that decreased consumption of a test meal induced by sibutramine is primarily because of reduced eating rate, enhancing the deceleration in cumulative food intake within a meal associated with the development of satiety. Changes in within-meal appetite ratings appear particularly sensitive to drug-induced enhancement of satiation, and may provide key indices for assessing the therapeutic potential of novel anti-obesity drugs.

Consumption of the slow-digesting waxy maize starch leads to blunted plasma glucose and insulin response but does not influence energy expenditure or appetite in humans

Limited research in humans suggests that slowly digestible starch may blunt the postprandial increase and subsequent decline of plasma glucose and insulin concentrations, leading to prolonged energy availability and satiety, compared to more rapidly digestible starch. This study examined the postprandial metabolic and appetitive responses of waxy maize starch (WM), a slow-digestible starch. It was hypothesized that the waxy maize treatment would result in a blunted and more sustained glucose and insulin response, as well as energy expenditure and appetitive responses. Twelve subjects (6 men and 6 women) (age, 23 +/- 1 years; body mass index, 22.2 +/- 0.7 kg/m(2); insulin sensitivity [homeostatic model assessment], 16% +/- 2%; physical activity, 556 +/- 120 min/wk) consumed, on separate days, 50 g of available carbohydrate as WM, a maltodextrin-sucrose mixture (MS), or white bread (control). Postprandial plasma glucose and insulin, energy expenditure, and appetite (hunger, fullness, desire to eat) were measured over 4 hours. Compared to control, the 4-hour glucose response was not different for MS and WM, and the 4-hour insulin response was higher for MS (P < .005) and lower for WM (P < .05). Compared to MS, WM led to lower 4-hour glucose and insulin responses (P < .001). These differences were driven by blunted glucose and insulin responses during the first hour for WM. Postprandial energy expenditure and appetite were not different among treatments. These results support that WM provides sustained glucose availability in young, insulin-sensitive adults.

Age and physical activity status effects on appetite and mood state in older humans

This study examined the influences of age and chronic physical activity status on appetite and mood state. Groups of younger inactive, younger active, older inactive, and older active men and women completed questionnaires each waking hour, rating appetite and mood state for 1 day. Maximal oxygen consumption was 20% lower in older than in younger (p < 0.001) subjects, and 32% lower in inactive than in active (p < 0.001) subjects. Mean hunger (older, 4 +/- 1; younger, 5 +/- 1 arbitrary units (AU); p < 0.01) and desire to eat (older, 3 +/- 1; younger, 4 +/- 1 AU; p < 0.01) were lower in older than in younger subjects. Nadir arousal was higher for the active subjects (active, 3 +/- 1; inactive, 2 +/- 1 AU; p < 0.05). Nadir arousal, nadir pleasantness, and mean pleasantness were higher for the older subjects (p < 0.05). Physical activity status does not influence appetite or the age-associated declines in hunger or desire to eat. The increased nadir arousal of the physically active and older groups is consistent with these subjects experiencing less extreme sleepiness.

Associations between macronutrient intake and self-reported appetite and fasting levels of appetite hormones: results from the Optimal Macronutrient Intake Trial to Prevent Heart Disease

The authors compared effects of macronutrients on self-reported appetite and selected fasting hormone levels. The Optimal Macronutrient Intake Trial to Prevent Heart Disease (OMNI-Heart) (2003-2005) was a randomized, 3-period, crossover feeding trial (n = 164) comparing the effects of 3 diets, each rich in a different macronutrient. Percentages of kilocalories of carbohydrate, fat, and protein were 48, 27, and 25, respectively, for the protein-rich diet; 58, 27, and 15, for the carbohydrate-rich diet; and 48, 37, and 15 for the diet rich in unsaturated fat. Food and drink were provided for each isocaloric 6-week period. Appetite was measured by visual analog scales. Pairwise differences between diets were estimated using generalized estimating equations. Compared with the protein diet, premeal appetite was 14% higher on the carbohydrate (P = 0.01) and unsaturated-fat (P = 0.003) diets. Geometric mean leptin was 8% lower on the protein diet than on the carbohydrate diet (P = 0.003). Obestatin levels were 7% and 6% lower on the protein diet than on the carbohydrate (P = 0.02) and unsaturated-fat (P = 0.004) diets, respectively. There were no between-diet differences for ghrelin. A diet rich in protein from lean meat and vegetables reduces self-reported appetite compared with diets rich in carbohydrate and unsaturated fat and can be recommended in a weight-stable setting. The observed pattern of hormone changes does not explain the inverse association between protein intake and appetite.

Medications for weight reduction

Only two drugs are currently approved for long-term use in the treatment of obesity and four others for short-term use. Evaluating the risk-benefit profile is an essential first step. For individuals who have a low body mass index for whom the risk is small, the risk profile must make the drug acceptable for almost everyone. For higher-risk patients, such as those planning intestinal bypass or who have sleep apnea, a wider range of drugs may be considered. Obesity is a chronic disease that has many causes. Treatment is aimed at palliation-that is, producing and maintaining weight loss. Regardless of the primary site of action, the net effect must be a reduction in food intake or increase in energy expenditure.