Appetite control and energy balance regulation in the modern world: reward-driven brain overrides repletion signals

Contrasting frontal cortical responses to food versus money rewards across BMI groups

Previous research has linked obesity with an altered perception of rewards. This study aimed to contrast frontal cortical activities across body mass index (BMI) groups, in responding to differential rewards (monetary versus food). A total of 60 male participants (27.43 ± 6.07 years of age; 21 normal weight [BMI: 18.5-24.9 kg·m-2]; 20 overweight [BMI: 25.0-29.9 kg·m-2]; and 19 individuals with obesity [BMI ≥ 30 kg·m-2]) were tested for their response bias towards food and money rewards using the Probabilistic Reward Task (PRT), while their frontal cortical responses were recorded using electroencephalography (EEG). The feedback-related negativity (FRN), a reliable measure of reward valuation and learning, was calculated for food (FRN(Food)) and money (FRN(Money)). Results indicate a left-lateralised frontal cortical activity associated with the food reward condition, in the group of overweight and obesity. In contrast, a right-lateralisation was observed in the money reward condition only in the group with obesity. More specifically, FRN(Food) was shown to significantly differ between left and right frontal cortical areas among individuals with obesity (p = 0.035) and overweight (p = 0.012), but not in normal-weight individuals (p = 0.153). Additionally, results revealed that FRN(Food) and FRN(Money) were significantly different for individuals with obesity (p = 0.019), but such a significant difference was not evident in the overweight and normal-weight individuals (p ≥ 0.05). These findings offer intriguing new insights into neuropsychological differentiation across BMI groups, adding to the understanding of obesity-related behaviour.

A small switch in perspective: Comparing weight loss by nutrient balance versus caloric balance

The establishment of a Caloric balance has been classically discussed as the means to induce weight loss. Recently, the idea of nutrient balance as opposed to Caloric balance has emerged as a better means to induce weight loss. This investigation compared differences in weight loss between a diet based on a nutrient balanced diet compared to a Caloric balance diet. 53 (27M/26F) active overfat individuals (30.7+/- 7.1 years) were randomly (matched for age, gender, training history) assigned within an 8-week intervention to follow either a self-selected diet (control) or a diet based on following a Caloric balance (%Cal/day) or a nutrient balance (g/kg/day) in conjunction with a periodized exercise regimen to determine effectiveness for each diet to induce weight loss. Nutrient balance group had significantly different changes (p < 0.05) in fat-free mass (2.26 (2.02, 2.49) kg versus 0.42 (-0.40, 1.24) kg) and fat mass (-5.96 (-5.34, -6.58) kg versus -4.08 (-3.92, -5.92) kg) relative to the Caloric balance group and was more effective at meeting nutritional requirements for protein (ES = 0.65 (0.48, 0.85)) and lipids (ES = 0.24 (-0.09, 0.98)) than the Caloric balance group. Nutrient balance was subjectively scored as easier to follow and more likely to be self-selected. Using a nutrient balance diet may be more effective at inducing beneficial body compositional changes and shows being a more self-selected dietary method when compared to a Caloric balance diet. Therefore, it may be a better choice for advice when offering treatments to those who are attempting to lose weight or maintain weight loss.

Longitudinal associations between psychosomatic and emotional status and selected food portion sizes in European children and adolescents: IDEFICS/I.Family study

This study aims to investigate the influence of psychosomatic and emotional status on food portion sizes (PSs) consumption from high energy-dense food groups in European children and adolescents. We hypothesized that psychosomatic and emotional status would have a significant association with the PS selection of energy-dense food. The study included 7355 children aged between 2 and 9.9 years at baseline (T0) (48.8% females); 3869 after 2 years (T1) (48.2% females), and 2971 (51.8% females) after 6 years of follow-up (T3). Psychosomatic and emotional status were measured using emotional well-being during the last week score (KINDL) and Strengths and Difficulties Questionnaire. PS was calculated from daily food intake recorded in 24-hour dietary recalls. The associations between emotional status indicators and PS from selected energy-dense food groups were assessed by multilevel linear regression models. In the cross-sectional analysis, we observed that higher KINDL scores were linked to lower PS consumption from sweet bakery products and savory snacks in both genders. Moreover, we found that adolescent females with high emotional and peer problem scores tended to consume larger PS of carbohydrate-rich and sugar-fatty food items (P < .017). Longitudinally, higher peer problem scores were associated with increased PS from bread and rolls, margarine and lipids, and dairy products in all genders and age groups (P< .017). In adolescents, psychosomatic and emotional status could be a trigger for consuming large PS from carbohydrate-rich and sugar-fatty energy-dense foods. Thus, nutritional interventions should consider emotional status to decrease unhealthy dietary habits in children and adolescents.

Interindividual variability in appetitive sensations and relationships between appetitive sensations and energy intake

BACKGROUND

Appetitive sensations (AS) are signals that guide eating behaviors. Marked short-term inter-individual variability in AS has been reported but the long-term stability of individual ratings and their dietary implications are not well characterized.

OBJECTIVES

This study explored the stability of inter-individual ratings of hunger, fullness and thirst for 17 weeks; determined the relationships between these sensations, eating patterns and energy intake (EI); as well as the associations between ratings and selected individual characteristics (age, gender, BMI).

METHODS

A 17-week observational study collected hourly appetitive ratings and dietary intake data from 97 (90 completers, 7 partial completers) healthy adults at weeks 1, 9, and 17.

RESULTS

There were marked and stable inter-individual differences over the 17 weeks for hunger (week 1 vs. week 9, r = 0.72 (p < 0.001); week 1 vs. week 17, r = 0.67 (p < 0.001); week 9 vs. week 17, r = 0.77 (p < 0.001)); fullness (week 1 vs. week 9 r = 0.74 (p < 0.001); week 1 vs. week 17, r = 0.71 (p < 0.001); week 9 vs. week 17, r = 0.81 (p < 0.001)); and thirst (week 1 vs. week 9 r = 0.82 (p < 0.001); week 1 vs. week 17, r = 0.81 (p < 0.001); week 9 vs. week 17, r = 0.88 (p < 0.001)). Cross-correlation functions revealed EI and eating pattern exerted stronger effects on AS than the reverse. However, the absolute effect sizes were small. Path analyses also indicated that there were weak relationships between AS and EI. No robust effects of the studied individual characteristics were observed.

CONCLUSION

This study found that acute and chronic sensations of hunger, fullness and thirst are relatively stable within individuals but vary markedly between individuals. In addition, the present data indicate AS are poorly associated with dietary patterns or with EI under conditions of relatively stable energy balance.

Dietary habits, depression and obesity: an intricate relationship to explore in pediatric preventive strategies

Obesity and depression represent major health problems due to their high prevalence and morbidity rates. Numerous evidences elucidated the connections between dietary habits and the incidence or severity of depression. This overview aims to investigate the intricate relationship between dietary patterns and depression with the objective of elaborating preventive strategies for childhood obesity. Literature data recognized that there is a link between mood and food choices, with certain foods selected for their impact on the brain's reward centers. This behavior parallels the one observed in substance addiction, suggesting a specific neural mechanism for food addiction that contributes to overeating and obesity. It is important to note the significant correlation between obesity and depression, indicating a shared biological pathway influencing these conditions. Stress substantially affects also eating behaviors, often leading to increased consumption of pleasurable and rewarding foods. This can trigger a cycle of overeating, weight gain, and psychological distress, exacerbating mood disorders and obesity. In addition, consumption of certain types of foods, especially "comfort foods" high in fat and calories, may provide temporary relief from symptoms of depression, but can lead to long-term obesity and further mental health problems. Understanding these complex interactions is critical to developing preventive strategies focusing on dietary, emotional, and environmental factors, thereby reducing the risk of obesity and mood disorders.

Adaptive and maladaptive emotion regulation skills are associated with food intake following a hunger-induced increase in negative emotions

Many individuals would like to lose weight and often attempt to do so by dieting. However, dieting attempts often backfire and contribute to the risk of weight gain and obesity. Food restriction inevitably leads to hunger and hunger, in turn, induces negative emotions. The inability to regulate such a hunger-induced increase in negative emotions in an adaptive way may be responsible for overeating. The current study aimed to gain a better understanding of this potential psychological mechanism underlying failed dieting attempts. Adaptive and maladaptive emotion regulation (ER) were assessed with an online questionnaire in women with a healthy weight. Subsequently, participants were assigned to the fasted condition (fasting for 14h, n = 49) or the satiated condition (eating between 2 h and 30 min before the lab session, n = 59) and attended a lab session in which they completed tasks while given the opportunity to eat chips and M&M's. We did not find an association between any ER variable and the likelihood to begin eating. Among those who began eating, higher scores on adaptive cognitive ER and on maladaptive behavioral ER were associated with lower caloric intake in fasted individuals. Higher scores on adaptive behavioral ER were associated with higher caloric intake in fasted individuals. Utilizing adaptive cognitive ER when experiencing a hunger-induced increase in negative emotions may help individuals manage their food intake and maintain a healthy weight.

Obesity and its impact on female reproductive health: unraveling the connections

In the modern era, the escalating global prevalence of obesity has profound implications on female reproductive health. Obesity, transcending mere lifestyle choices, has evolved into a complex disorder affecting physiological and metabolic functions. Concurrently, female infertility is rising as a significant global health issue. Obesity, with its extensive systemic effects, is pinpointed as a major disruptor. The convergence of these health challenges reveals a multifaceted scenario: on one hand, obesity directly impacts female reproductive health, particularly in the context of conditions like polycystic ovary syndrome (PCOS) and menstrual disturbances; on the other, the psychosocial consequences of infertility might intensify weight-gain patterns, forming a challenging cycle. Additionally, the economic implications of treating obesity-related infertility are considerable. This review delves into the myriad ways obesity affects female reproductive health, drawing insights from epidemiological, clinical, and molecular studies. It explores the epidemiological relationship between obesity and PCOS, the influence of obesity on menstrual disturbances, and the broader impact of obesity on female infertility. Weight loss, through pharmacological interventions, surgical methods, or lifestyle adjustments, emerges as a promising strategy. Lastly, the efficacy of assisted reproductive technologies, such as IVF, is influenced by obesity, underscoring the importance of an optimal body mass index. The review also highlights the molecular and physiological mechanisms underlying the impact of obesity on female reproductive health, including the disruption of the hypothalamic-pituitary-ovary axis, altered adipokine secretion, and the role of chronic inflammation and oxidative stress.

Applying psycho-behavioural phenotyping in obesity characterization

Individual differences in obesity, beyond being explained by metabolic and medical complications, are understood by alterations in eating behaviour which underlie psychological processes. From this psychological perspective, studies have identified several potential characteristic features at the psycho-behavioural level that could additionally explain the maintenance of chronic excess weight or the unsuccessful results of current treatments. To date, despite the growing evidence, the heterogeneity of the psychological evidence associated with obesity has made it challenging to generate consensus on whether these psycho-behavioural phenotypes can be a complement to improve outcomes of existing interventions. For this reason, this narrative review is an overview focused on summarizing studies describing the psycho-behavioural phenotypes associated with obesity. Based on the literature, three psychological constructs have emerged: reward dependence, cognitive control, and mood and emotion. We discuss the clinical implications of stratifying and identifying these psycho-behavioural profiles as potential target for interventions which may ensure a better response to treatment in individuals with obesity. Our conclusions pointed out a considerable overlap between these psycho-behavioural phenotypes suggesting bidirectional interactions between them. These findings endorse the complexity of the psycho-behavioural features associated with obesity and reinforce the need to consider them in order to improve treatment outcomes.

Acute effect of high-intensity interval training versus moderate-intensity continuous training on appetite perception: A systematic review and meta-analysis

Interval training protocols have gained popularity over the years, but their impact on appetite sensation compared to officially recommended training method, moderate intensity continuous training (MICT) is not well understood. Thus, this systematic review and meta-analysis aimed to compare a single session of high intensity interval training (HIIT) including sprint interval training (SIT) with MICT on appetite perception measured by the visual analog scale (VAS). After searching up articles published up to September 2021, 13 randomized controlled studies were included in the meta-analysis. Outcomes of meta-analysis demonstrated that both acute sessions of HIIT/SIT and MICT suppressed appetite compared to no-exercise control groups immediately post exercise but there were no significant effects 30-90 min post exercise or in AUC values, indicating a transient effect of exercise on appetite sensations. Moreover, differences in appetite sensations between HIIT/SIT and MICT were negligible immediately post exercise, but HIIT/SIT suppressed hunger (MD = -6.347 [-12.054, -0.639], p = 0.029) to a greater extent than MICT 30- to 90-min post exercise, while there was a lack of consistency other VAS subscales of appetite. More studies that address the impact of exercising timing, nutrient compositions of energy intake (energy intake (EI)) and differences in participants' characteristics and long-term studies analyzing chronic effects are needed to comprehensively examine the differences between HIIT/SIT and MICT on appetite and EI. SYSTEMATIC REVIEW REGISTRATION: [https://www.crd.york.ac.uk/PROSPERO], Identifier [CRD42021284898].

A Proof-of-Concept Pilot Test of a Behavioral Intervention to Improve Adherence to Dietary Recommendations for Cancer Prevention

OBJECTIVES

Prevention programs that can help adults improve the quality of their diets to reduce cancer risk are needed. This Phase IIa study prospectively tested a mHealth intervention designed to improve adherence to dietary quality guidelines for cancer prevention.

METHODS

All participants (N = 62) received nutrition education and a self-regulation skills curriculum, with a primary target of changing grocery shopping behavior. Using a randomized, factorial design, the study varied whether each of the following 4 components were added to the 20-week intervention: (1) location-triggered app messaging, delivered when individuals arrived at grocery stores, (2) reflections on benefits of change, delivered with extra coaching time and tailored app messages, (3) coach monitoring, in which food purchases were digitally monitored by a coach, and (4) involvement of a household member in the intervention.

RESULTS

Benchmarks were successfully met for recruitment, retention, and treatment acceptability. Across conditions, there were significant reductions in highly processed food intake (P < .001, η2 = .48), red and processed meat intake (P < .001, η2 = .20), and sugar-sweetened beverage intake (P = .008, η2 = .13) from pre-to post-treatment. Analyses examining whether each intervention component influenced change across time found that participants who received coach monitoring increased their intake of fruits, vegetables, and fiber, whereas those with no coach monitoring had less improvement (P = .01, η2 = .14). The improvement in red and processed meat was stronger among participants with household support ON, at a marginally significant level, than those with household support OFF (P = .056, η2 = .07).

CONCLUSION

This study showed feasibility, acceptability, and preliminary signals of efficacy of a remotely delivered intervention to facilitate adherence to dietary guidelines for cancer prevention and that coach monitoring and household support may be especially effective strategies. A fully powered clinical trial is warranted to test an optimized version of the intervention that includes nutrition education, self-regulation skills training, coach monitoring, and household member involvement.

TRIAL REGISTRATION

ClinicalTrials.gov NCT04947150.

Understanding and co-managing medication treatment options for opioid use disorder

The number of patients with opioid use disorder (OUD) has increased dramatically. Substance use disorders in general are thought to occur in one in five patients in primary care. However, despite this prevalence, there is a dearth of training in undergraduate and continuing medical education to manage OUDs, and internal medicine doctors need to have an understanding of the basic physiology and treatment options for this illness. Expanding knowledge of OUD treatments will allow internists to use their skills and strong patient-doctor relationships to ensure the trust of their patients with OUD, leading to better outcomes and increased chances of recovery. It will also allow clinicians to appropriately refer their patients for lifesaving specialized care and help them prevent dangerous medical complications often seen as a result of addiction. There are three FDA-approved medications to treat OUD disorder, known collectively as medication-assisted treatment (MAT). In this paper, the three medications-methadone, naltrexone, and buprenorphine-are presented, compared, contrasted, and clinically reviewed.

Plasma Leptin and Adiponectin after a 4-Week Vegan Diet: A Randomized-Controlled Pilot Trial in Healthy Participants

Adiponectin and leptin are important mediators of metabolic homeostasis. The actions of these adipokines extend beyond adipocytes and include systemic modulation of lipid and glucose metabolism, nutrient flux, and the immune response to changes in nutrition. Herein, we hypothesized that short-term intervention with a vegan diet might result in an improvement of plasma concentrations of adiponectin and leptin and the leptin/adiponectin ratio. We investigated the response of plasma adiponectin and leptin to a 4-week intervention with a vegan or meat-rich diet and its associations with sex, BMI and nutritional intake. Fifty-three healthy, omnivore participants (62% female, average age 31 years and BMI 23.1 kg/m²) were randomly assigned to a vegan or meat-rich diet for 4 weeks. Plasma adiponectin and leptin were lower in men compared to women both at the beginning and end of the trial. The concentration of adiponectin in women was significantly higher both when comparing their transition from omnivorous to vegan diet (p = 0.023) and also for vegan versus meat-rich diet at the end of the trial (p = 0.001), whereas plasma leptin did not vary significantly. No changes in adiponectin were identified in men, yet an increase in leptin occurred upon their transition from an omnivorous to a meat-rich diet (p = 0.019). Examination of plasma adiponectin/leptin ratio, a proposed marker of cardiovascular risk, did not differ after 4-weeks of dietary intervention. Our study revealed that adiponectin and leptin concentrations are sensitive to short-term dietary intervention in a sex-dependent manner. This dietary modification of leptin and adiponectin not only occurs quickly as demonstrated in our study, but it remains such as published in studies with individuals who are established (long-term) vegetarians compared to omnivorous.

Metabolic hormones mediate cognition

Recent biochemical and behavioural evidence indicates that metabolic hormones not only regulate energy intake and nutrient content, but also modulate plasticity and cognition in the central nervous system. Disruptions in metabolic hormone signalling may provide a link between metabolic syndromes like obesity and diabetes, and cognitive impairment. For example, altered metabolic homeostasis in obesity is a strong determinant of the severity of age-related cognitive decline and neurodegenerative disease. Here we review the evidence that eating behaviours and metabolic hormones-particularly ghrelin, leptin, and insulin-are key players in the delicate regulation of neural plasticity and cognition. Caloric restriction and antidiabetic therapies, both of which affect metabolic hormone levels can restore metabolic homeostasis and enhance cognitive function. Thus, metabolic hormone pathways provide a promising target for the treatment of cognitive decline.

Optimizing an mHealth Intervention to Change Food Purchasing Behaviors for Cancer Prevention: Protocol for a Pilot Randomized Controlled Trial

BACKGROUND

Dietary intake is a powerful modifiable factor that influences cancer risk; however, most US adults do not adhere to dietary guidelines for cancer prevention. One promising pathway for improving dietary adherence is targeting grocery shopping habits. Interventions might facilitate healthy grocery choices, with a combination of mHealth and traditional methods, by promoting the salience of dietary goals while shopping, enhancing motivation to make dietary changes, and increasing household support for healthy food purchasing.

OBJECTIVE

This pilot study will assess feasibility and acceptability of intervention components designed to improve adherence to dietary guidelines for cancer prevention (preliminary aim). The primary aim of the study is to quantify the effect of each intervention component, individually and in combination, on dietary intake (primary aim) and grocery store food purchases (exploratory aim). Mediation analyses will be conducted to understand the mechanisms of action (goal salience, motivation, and household support-secondary aims). The overarching goal is to optimize an mHealth intervention to be tested in a future fully powered clinical trial.

METHODS

The study enrolled adults (N=62) with low adherence to dietary recommendations for cancer prevention. In a 20-week program, all participants attend a nutrition education workshop and receive weekly educational messages through an app. A factorial design is used to test 4 intervention components: (1) location-triggered messages: educational messages are delivered when arriving at grocery stores; (2) reflections on the benefits of change: content is added to messages to encourage reflection on anticipated benefits of healthy eating, and participants attend an additional workshop session and 3 coach calls on this topic; (3) coach monitoring: food purchases are monitored digitally by a coach who sends personalized weekly app messages and conducts 3 coaching calls that focus on feedback about purchases; and (4) household support: another adult in the household receives messages designed to elicit support for healthy food purchasing, and support is addressed in 3 coach calls and an extra workshop session attended by the index participant and household member. Assessments are completed at weeks 0, 10, and 20 using self-report measures, as well as objective capture of grocery data from the point of purchase using store loyalty accounts.

RESULTS

The National Cancer Institute funded this study (R21CA252933) on July 7, 2020. Participant recruitment began in the spring of 2021 and concluded with the successful enrollment of 62 participants. Data collection is expected to be completed in the summer of 2022, and results are expected to be disseminated in the summer of 2023.

CONCLUSIONS

The results of this study will inform the development of scalable interventions to lower cancer risk via changes in dietary intake.

TRIAL REGISTRATION

ClinicalTrials.gov NCT04947150; https://clinicaltrials.gov/ct2/show/NCT04947150.

INTERNATIONAL REGISTERED REPORT IDENTIFIER (IRRID)

DERR1-10.2196/39669.

The Rise and Fall of Physiological Theories of the Control of Human Eating Behavior

Kuhns was the first to suggest that theories in science do not develop in small increments but rather in major leaps to paradigms that examine the same question through very different perspectives. Theories on the mechanism responsible for control of human food intake fall into Kuhn’s description. This article describes how the two major theories of the control of food intake in humans, the Glucostatic Theory, and the Lipostatic Theory, showed initial promise as explanations, but later deteriorated with the slow accumulation experimental data. The locus of theories considered eating behavior as a part of physiological system that regulates the storage of energy on the body. We challenge this fundamental belief with data which suggests that we must be ready to accept a major change in the way we think about eating behavior if we are ever to decrease the prevalence of obesity.

Regulation of appetite-related neuropeptides by Panax ginseng: A novel approach for obesity treatment

Obesity is a primary factor provoking various chronic disorders, including cardiovascular disease, diabetes, and cancer, and causes the death of 2.8 million individuals each year. Diet, physical activity, medications, and surgery are the main therapies for overweightness and obesity. During weight loss therapy, a decrease in energy stores activates appetite signaling pathways under the regulation of neuropeptides, including anorexigenic [corticotropin-releasing hormone, proopiomelanocortin (POMC), cholecystokinin (CCK), and cocaine- and amphetamine-regulated transcript] and orexigenic [agouti-related protein (AgRP), neuropeptide Y (NPY), and melanin-concentrating hormone] neuropeptides, which increase food intake and lead to failure in attaining weight loss goals. Ginseng and ginsenosides reverse these signaling pathways by suppressing orexigenic neuropeptides (NPY and AgRP) and provoking anorexigenic neuropeptides (CCK and POMC), which prevent the increase in food intake. Moreover, the results of network pharmacology analysis have revealed that constituents of ginseng radix, including campesterol, beta-elemene, ginsenoside Rb1, biotin, and pantothenic acid, are highly correlated with neuropeptide genes that regulate energy balance and food intake, including ADIPOQ, NAMPT, UBL5, NUCB2, LEP, CCK, GAST, IGF1, RLN1, PENK, PDYN, and POMC. Based on previous studies and network pharmacology analysis data, ginseng and its compounds may be a potent source for obesity treatment by regulating neuropeptides associated with appetite.

Satiety Associated with Calorie Restriction and Time-Restricted Feeding: Central Neuroendocrine Integration

This review focuses on summarizing current knowledge on how time-restricted feeding (TRF) and continuous caloric restriction (CR) affect central neuroendocrine systems involved in regulating satiety. Several interconnected regions of the hypothalamus, brainstem, and cortical areas of the brain are involved in the regulation of satiety. Following CR and TRF, the increase in hunger and reduction in satiety signals of the melanocortin system [neuropeptide Y (NPY), proopiomelanocortin (POMC), and agouti-related peptide (AgRP)] appear similar between CR and TRF protocols, as do the dopaminergic responses in the mesocorticolimbic circuit. However, ghrelin and leptin signaling via the melanocortin system appears to improve energy balance signals and reduce hyperphagia following TRF, which has not been reported in CR. In addition to satiety systems, CR and TRF also influence circadian rhythms. CR influences the suprachiasmatic nucleus (SCN) or the primary circadian clock as seen by increased clock gene expression. In contrast, TRF appears to affect both the SCN and the peripheral clocks, as seen by phasic changes in the non-SCN (potentially the elusive food entrainable oscillator) and metabolic clocks. The peripheral clocks are influenced by the primary circadian clock but are also entrained by food timing, sleep timing, and other lifestyle parameters, which can supersede the metabolic processes that are regulated by the primary circadian clock. Taken together, TRF influences hunger/satiety, energy balance systems, and circadian rhythms, suggesting a role for adherence to CR in the long run if implemented using the TRF approach. However, these suggestions are based on only a few studies, and future investigations that use standardized protocols for the evaluation of the effect of these diet patterns (time, duration, meal composition, sufficiently powered) are necessary to verify these preliminary observations.

Taste of Fat and Obesity: Different Hypotheses and Our Point of View

Obesity results from a temporary or prolonged positive energy balance due to an alteration in the homeostatic feedback of energy balance. Food, with its discriminative and hedonic qualities, is a key element of reward-based energy intake. An alteration in the brain reward system for highly palatable energy-rich foods, comprised of fat and carbohydrates, could be one of the main factors involved in the development of obesity by increasing the attractiveness and consumption of fat-rich foods. This would induce, in turn, a decrease in the taste of fat. A better understanding of the altered reward system in obesity may open the door to a new era for the diagnosis, management and treatment of this disease.

Food Consciousness Intervention Improves Interoceptive Sensitivity and Expression of Exteroception in Women

The perception of the body’s internal state (interoception) and the perception and processing of environmental sensory stimuli (exteroception) act together to modulate adaptive behaviour, including eating behaviour, and are related to bodyweight control. This study evaluated the impact of the Food and Nutrition Education Program with Sensory and Cognitive Exercises on interoceptive sensitivity and on the expression of exteroceptive perception in women who experienced difficulty in controlling their body weight. Thirty-seven women were randomized into two groups and evaluated at two moments: before and after the intervention or before and after a 3- to 4-week waiting period. A heartbeat tracking task was used for interoception evaluation. Participants were asked to write a text describing three foods after tasting them for exteroception evaluation. After the intervention, the participants showed an increase in interoceptive sensitivity, and an increase in the expression of exteroceptive stimuli perception through a semantic assessment of their writing related to the tasting experience. In addition, the results point to a possible connection between the mechanisms governing interoception and exteroception. This work brings important contributions to the search for strategies capable of promoting the perception and integration of physiological and environmental stimuli in food consumption.

Serotonin and Dopamine Mimic Glucose-Induced Reinforcement in C. elegans: Potential Role of NSM Neurons and the Serotonin Subtype 4 Receptor

Food produces powerful reinforcement that can lead to overconsumption and likely contributes to the obesity epidemic. The present studies examined molecular mechanisms mediating food-induced reinforcement in the model system C. elegans. After a 1-h training session during which food (bacteria) is paired with the odorant butanone, odor preference for butanone robustly increased. Glucose mimicked this effect of bacteria. Glucose-induced odor preference was enhanced similarly by prior food withdrawal or blocking glucose metabolism in the presence of food. Food- and glucose-induced odor preference was mimicked by serotonin signaling through the serotonin type-4 (5-HT4) receptor. Dopamine (thought to act primarily through a D1-like receptor) facilitated, whereas the D2 agonist bromocriptine blocked, food- and glucose-induced odor preference. Furthermore, prior food withdrawal similarly influenced reward produced by serotonin, dopamine, or food, implying post-synaptic enhancement of sensitivity to serotonin and dopamine. These results suggest that glucose metabolism plays a key role in mediating both food-induced reinforcement and enhancement of that reinforcement by prior food withdrawal and implicate serotonergic signaling through 5-HT4 receptor in the re-enforcing properties of food.

Intranasal oxytocin reduces attentional bias to food stimuli

Attentional biases to food-related stimuli have been demonstrated in response to hunger as well as during restrained eating. Such biases are often associated with obesity, but healthy-weight individuals who do not self-report hunger have also demonstrated attentional biases to stimuli signalling food using laboratory-based cognitive tasks. Levels of the anorectic neuropeptide oxytocin are elevated by food intake and, when administered intranasally, oxytocin inhibits food intake in the laboratory. To investigate whether oxytocin can affect appetite via an action on attentional processes, 40 adults (29 women; mean age 24.0 years old) self-administered 24 IU of oxytocin or placebo intranasally. Forty minutes after administration, participants ate a small snack to maintain alertness and ameliorate deprivation-induced hunger before starting a computerized dot-probe attentional bias task that presented 180 trials of paired visual stimuli comprising neutral, food, social and/or romantic images (500 ms presentation time). Reaction times to probe stimuli that appeared after the offset of the visual images indicated a significant attentional bias to food pictures after placebo; this effect was significantly attenuated by oxytocin, p < .001. The effect of oxytocin on attentional bias to the food pictures was not altered by the type of stimulus paired with the food image, and was independent of BMI, age, sex, self-rated eating behaviour, and self-reported parental bonding; however, the effect was modulated by self-reported food cravings and trait stress. The findings support and extend previous work which has suggested that oxytocin can counteract attentional biases to food-related stimuli in a sample with anorexia by demonstrating the same effect for the first time in a cohort who do not have an eating disorder.

The transdiagnostic role of food craving: An application of substance use models

Food craving is a transdiagnostic process underlying clinically significant disordered eating behaviors and eating disorder diagnoses. However, the lack of literature examining the role of food craving as it relates to the full spectrum of disordered eating behaviors, including restrictive eating and compensatory behaviors, may be due to the traditional definition of food craving as the desire to consume particular foods. Applying motivational models of substance use craving to food craving may help to explain inconsistencies within existing literature. Three motivational models of craving from the substance use literature may be particularly applicable to (1) provide a clear definition of food craving as a motivational process, (2) understand the role of that motivational process as it underlies the full spectrum of disordered eating behavioral patterns, (3) provide insight for the most appropriate ways in which to accurately assess food craving, and (4) establish ways in which food craving may represent a useful motivational process to target in eating disorder treatments. This narrative review describes three models of substance use craving and provides suggestions for utilizing motivational models to understand the transdiagnostic role of food craving as it relates to the full spectrum of disordered eating behaviors in both research and clinical work.

Association Between Family Physical Violence Victimization and Food Consumption Among Brazilian Adolescents

Few studies have evaluated the relationship between stressful events, such as child abuse and food consumption. Thus, the objective of this study is to assess whether family physical violence victimization is associated with food consumption in adolescents. We used data from the Brazilian National Adolescent School-based Health Survey, carried out in 2015, in a representative sample of 102,072 students attending ninth grade from public and private schools. We used Venn diagrams and logistic regression analysis to, respectively, graphically represent and evaluate the association between the consumption of ultra-processed food (soft drinks, sweets/candies, and salty biscuits, packaged snacks, or processed meat) and in natura food (beans, fruits and vegetables) with victimization from family physical violence. We found a lower consumption of in natura and higher consumption of ultra-processed foods among adolescent victims when compared with nonvictims of family physical violence. The probability of consuming 4 or more times a week increased by 44% for salty biscuits, packaged snacks, or processed meats; 38% for soft drinks; and 22% for sweets among adolescents who reported violence. On the contrary, the probability of consuming 4 or more times a week decreased by 25% for beans, 19% for vegetables, and 13% for fruits among adolescent victims of family physical violence. We conclude that family physical violence victimization is associated with high consumption of ultra-processed food and low consumption of in natura food among Brazilian adolescents. Therefore, issues related to violence in childhood and adolescence should be addressed in interventions aimed at altering food consumption and consequent prevention, control, and treatment of nutrition-related outcomes to increase their effectiveness.

Post-oral sensing of fat increases food intake and attenuates body weight defense

In mammals, changes in weight elicit responses that favor a return to one's previous weight and promote weight stability. It has been hypothesized that palatable sweet and high-fat foods disturb the defense of body weight, leading to weight gain. We find that increasing sweetness or percent calories from fat increases diet palatability but that only increases in nutritive fat content increase caloric intake and body weight. In a mouse model of overfeeding that activates weight defense, high-fat diets, but not sweetened diets, attenuate the defense of body weight, leading to weight gain. The ability of a palatable, high-fat diet to increase food intake does not require tasting or smelling the food. Instead, the direct infusion of a high-fat diet into the stomach increases the ad libitum intake of less palatable, low-fat food. Post-oral sensing of percent calories from fat modulates feeding behavior to alter weight stability.

Is Food Addictive? A Review of the Science

As ultraprocessed foods (i.e., foods composed of mostly cheap industrial sources of dietary energy and nutrients plus additives) have become more abundant in our food supply, rates of obesity and diet-related disease have increased simultaneously. Food addiction has emerged as a phenotype of significant empirical interest within the past decade, conceptualized most commonly as a substance-based addiction to ultraprocessed foods. We detail (a) how approaches used to understand substance-use disorders may be applicable for operationalizing food addiction, (b) evidence for the reinforcing potential of ingredients in ultraprocessed foods that may drive compulsive consumptions, (c) the utility of conceptualizing food addiction as a substance-use disorder versus a behavioral addiction, and (d) clinical and policy implications that may follow if ultraprocessed foods exhibit an addictive potential. Broadly, the existing literature suggests biological and behavioral parallels between food addiction and substance addictions, with ultraprocessed foods high in both added fat and refined carbohydrates being most implicated in addictive-like eating. Future research priorities are also discussed, including the need for longitudinal studies and the potential negative impact of addictive ultraprocessed foods on children. Expected final online publication date for the Annual Review of Nutrition, Volume 41 is September 2021. Please see http://www.annualreviews.org/page/journal/pubdates for revised estimates.

Life-course effects of early life adversity exposure on eating behavior and metabolism

Environmental variations in early life influence brain development, making individuals more vulnerable to psychiatric and metabolic disorders. Early life stress (ELS) has a strong impact on the development of eating behavior. However, eating is a complex behavior, determined by an interaction between signals of energy homeostasis, neuronal circuits involved in its regulation, and circuits related to rewarding properties of the food. Although mechanisms underlying ELS-induced altered feeding behavior are not completely understood, evidence suggest that the effects of ELS on metabolic, mood, and emotional disorders, as well as reward system dysfunctions can contribute directly or indirectly to altered feeding behavior. The focus of this chapter is to discuss the effects of ELS on eating behavior and metabolism, considering different factors that control appetite such as energy homeostasis, hedonic properties of the food, emotional and cognitive status. After highlighting classic studies on the association between ELS and eating behavior alterations, we discuss how exposure to adversity can interact with genetics characteristics to predict variable outcomes.

Body composition, not dietary fatty acid composition, explains metabolic responses following a high-fat meal in premenopausal normal-weight women: a single-blind, randomised, crossover study

The aim of this study was to examine the effect of three different fatty acid (FA)-rich meals enriched in either SFA, MUFA or PUFA on postprandial metabolic responses in premenopausal, normal-weight women. For this randomised, single-blind, crossover study, three high-fat (HF) meals rich in either SFA, MUFA or PUFA (65 % energy from fat; 35 % of participants’ total daily energy needs) were tested. For each visit, anthropometrics and RMR were measured following a 12–15 h fast. Then, participants consumed one of the HF meals, and respiratory gases were collected using indirect calorimetry for 3 h postprandially. Energy expenditure (EE) following a SFA-rich meal was significantly higher than a MUFA-rich meal (P = 0·04; η2 = 0·19), but SFA was not significantly different from PUFA. There was a trend towards significance in EE between PUFA and MUFA (P = 0·06). After adjusting for fat-free mass (FFM), there were no longer condition or time effects for EE, although FFM remained a significant predictor (P = 0·005; η2 = 0·45). There were no significant differences between conditions for dietary-induced thermogenesis or substrate oxidation. The relationship between fat mass (FM) and both total fat oxidation (r 0·62; P = 0·025) and total change in RER following a MUFA-rich meal was observed (r −0·55; P = 0·05). In conclusion, weight loss through increases in EE may be best achieved by increasing FFM rather than selection of FA type. Further, a relationship exists between FM and fat oxidation following a MUFA-rich meal, most likely due to an unidentified mechanism.

Effect of Physical Exercise on Taste Perceptions: A Systematic Review

The effect of physical exercise on nutrition has gained substantial interest in the last decade. Meaningful results have been produced concerning the effect of physical exercise on different appetite hormones and food choice/preference. While it is well known that taste and nutrition are related, the relation between taste and physical activity has not yet been fully explored. This systematic review aims to provide a detailed view of the literature on physical exercise and its effect on taste perceptions. Five tastes were included in this review: sweet, salty, bitter, sour, and umami. Sweet taste intensity, sensitivity, and preference were increased by acute physical exercise, but sweet preference was reduced by chronic physical activity. Perceived intensity and sensitivity decreased overall for salty taste, but an increased preference was noted during/following exercise. Sour taste intensity ratings were decreased following exercise and preference was enhanced. Umami taste intensity and sensitivity increased following exercise and preference was decreased. No significant results were obtained for bitter taste. While evidence regarding the effect of exercise on taste has arisen from this review, the pre-testing nutrition, testing conditions, type of test, and exercise modality must be standardized in order to produce meaningful and reproducible results in the future.

Negative Social Evaluation Impairs Executive Functions in Adolescents With Excess Weight: Associations With Autonomic Responses

BACKGROUND

Adolescents with excess weight suffer social stress more frequently than their peers with normal weight.

PURPOSE

To examine the impact of social stress, specifically negative social evaluation, on executive functions in adolescents with excess weight. We also examined associations between subjective stress, autonomic reactivity, and executive functioning.

METHODS

Sixty adolescents (aged 13-18 years) classified into excess weight or normal weight groups participated. We assessed executive functioning (working memory, inhibition, and shifting) and subjective stress levels before and after the Trier Social Stress Task (TSST). The TSST was divided into two phases according to the feedback of the audience: positive and negative social evaluation. Heart rate and skin conductance were recorded.

RESULTS

Adolescents with excess weight showed poorer executive functioning after exposure to TSST compared with adolescents with normal weight. Subjective stress and autonomic reactivity were also greater in adolescents with excess weight than adolescents with normal weight. Negative social evaluation was associated with worse executive functioning and increased autonomic reactivity in adolescents with excess weight.

CONCLUSIONS

The findings suggest that adolescents with excess weight are more sensitive to social stress triggered by negative evaluations. Social stress elicited deterioration of executive functioning in adolescents with excess weight. Evoked increases in subjective stress and autonomic responses predicted decreased executive function. Deficits in executive skills could reduce cognitive control abilities and lead to overeating in adolescents with excess weight. Strategies to cope with social stress to prevent executive deficits could be useful to prevent future obesity in this population.

Social transmission of food safety depends on synaptic plasticity in the prefrontal cortex

When an animal is facing unfamiliar food, its odor, together with semiochemicals emanating from a conspecific, can constitute a safety message and authorize intake. The piriform cortex (PiC) codes olfactory information, and the inactivation of neurons in the nucleus accumbens (NAc) can acutely trigger consumption. However, the neural circuit and cellular substrate of transition of olfactory perception into value-based actions remain elusive. We detected enhanced activity after social transmission between two mice in neurons of the medial prefrontal cortex (mPFC) that target the NAc and receive projections from the PiC. Exposure to a conspecific potentiated the excitatory postsynaptic currents in NAc projectors, whereas blocking transmission from PiC to mPFC prevented social transmission. Thus, synaptic plasticity in the mPFC is a cellular substrate of social transmission of food safety.

Changes in intake of plant-based diets and weight change: results from 3 prospective cohort studies

BACKGROUND

Studies have found beneficial effects of plant-based diets on weight. However, not all plant foods are necessarily beneficial.

OBJECTIVES

The aim of this study was to examine associations of changes in intake of 3 variations of plant-based diet indices (overall, healthful, and unhealthful) with weight change over 4-y intervals spanning >20 y.

METHODS

Data from 3 ongoing prospective observational cohort studies in the United States were used, namely the Nurses' Health Study (NHS), NHS2, and the Health Professionals Follow-up Study (HPFS), with 126,982 adult men and women. Self-reported diet data were collected every 4 y, and self-reported weight data were used to compute weight change every 4 y over >20 y of follow-up.

RESULTS

On average, participants gained a mean of 0.90 kg (HPFS) to 1.98 kg (NHS2) over 4-y intervals. Different types of plant-based diet indices were associated with different amounts of weight gain. After adjusting for several potential confounders, including concomitant changes in other lifestyle factors, a 1-SD increase in intake of an overall plant-based diet index was associated with 0.04 kg less weight gain over 4-y periods (95% CI: 0.05, 0.02 kg; P < 0.001). A 1-SD increase in intake of a healthful version of a plant-based diet index (emphasizing whole grains, fruits/vegetables, nuts/legumes, vegetable oils, tea/coffee) was associated with 0.68 kg less weight gain over 4-y periods (95% CI: 0.69, 0.66 kg; P < 0.001). Conversely, a 1-SD increase in an unhealthful version of a plant-based diet index (emphasizing refined grains, potato/fries, sweets, sweetened drinks/juices) was associated with 0.36 kg more weight gain (95% CI: 0.34, 0.37 kg, P < 0.001).

CONCLUSION

Plant-based diets, especially when rich in healthier plant foods, are associated with less weight gain over 4-y intervals. This supports current recommendations to increase intake of healthy plant foods, and reducing intake of less-healthy plant foods and animal foods, for improved health outcomes.

The pathogenesis of obesity

Body fat mass increases when energy intake exceeds energy expenditure. In the long term, a positive energy balance will result in obesity. The worldwide prevalence of obesity has increased dramatically, posing a serious threat to human health. Therefore, insight in the pathogenesis of obesity is important to identify novel prevention and treatment strategies. This review describes the physiology of energy expenditure and energy intake in the context of body weight gain in humans. We focus on the components of energy expenditure and the regulation of energy intake. Finally, we describe rare monogenetic causes leading to an impairment in central regulation of food intake and obesity.

Rapid Assessment of Reward-Related Eating: The RED-X5

OBJECTIVE

The prevalence of obesity has created a plethora of questionnaires characterizing psychological aspects of eating behavior, such as reward-related eating (RRE). The Reward-based Eating Drive questionnaires (RED-9, RED-13) broadly and deeply assess the RRE construct. However, large-sample research designs require shorter questionnaires that capture RRE quickly and precisely. This study sought to develop a brief, reliable, and valid version of the RED questionnaire.

METHODS

All-subset correlation was used to find a subset that maximally associated with the full RED-13 in two separate samples. Results were validated in a third independent sample. Internal consistency, test-retest reliability, and ability to explain variance in external outcomes were also assessed.

RESULTS

A five-item questionnaire (RED-X5) correlated strongly with RED-13 in the independent sample (r = 0.95). RED-X5 demonstrated high internal consistency (omega total ≥ 0.80) and 6-month test-retest reliability (r = 0.72). RED-X5 accurately reproduced known associations between RED-13 and BMI, diabetes status, and craving for sweet and savory foods. As a novel finding, RED questionnaires predicted laboratory intake of chips.

CONCLUSIONS

RED-X5 is a short, reliable, and valid measure of the RRE construct and can be readily implemented in large-sample research designs in which questionnaire space is limited.

Interactive effects of sleep duration and morning/evening preference on cardiovascular risk factors

Background

Sleep duration and morningness/eveningness (circadian preference) have separately been associated with cardiovascular risk factors (i.e. tobacco use, physical inactivity). Interactive effects are plausible, resulting from combinations of sleep homeostatic and circadian influences. These have not been examined in a population sample.

Methods

Multivariable regression models were used to test the associations between combinations of sleep duration (short [≤6 h], adequate [7-8 h], long [≥9 h]) and morning/evening preference (morning, somewhat morning, somewhat evening, evening) with the cardiovascular risk factors of tobacco use, physical inactivity, high sedentary behaviour, obesity/overweight and eating fewer than 5 daily servings of fruit and vegetables, in a cross-sectional sample of 439 933 adults enrolled in the United Kingdom Biobank project.

Results

Participants were 56% female, 95% white and mean age was 56.5 (SD = 8.1) years. Compared with adequate sleep with morning preference (referent group), long sleep with evening preference had a relative odds of 3.23 for tobacco use, a 2.02-fold relative odds of not meeting physical activity recommendations, a 2.19-fold relative odds of high screen-based sedentary behaviour, a 1.47-fold relative odds of being obese/overweight and a 1.62-fold relative odds of <5 fruit and vegetable daily servings. Adequate sleep with either morning or somewhat morning preference was associated with a lower prevalence and odds for all cardiovascular risk behaviours except fruit and vegetable intake.

Conclusions

Long sleepers with evening preference may be a sleep phenotype at high cardiovascular risk. Further work is needed to examine these relationships longitudinally and to assess the effects of chronotherapeutic interventions on cardiovascular risk behaviours.

Gut-brain axis and addictive disorders: A review with focus on alcohol and drugs of abuse

Due to the limited efficacy of existing medications for addictive disorders including alcohol use disorder (AUD), the need for additional medications is substantial. Potential new medications for addiction can be identified through investigation of the neurochemical substrates mediating the ability of drugs of abuse such as alcohol to activate the mesolimbic dopamine system. Interestingly, recent studies implicate neuropeptides of the gut-brain axis as modulators of reward and addiction processes. The present review therefore summarizes the current studies investigating the ability of the gut-brain peptides ghrelin, glucagon-like peptide-1 (GLP-1), amylin and neuromedin U (NMU) to modulate alcohol- and drug-related behaviors in rodents and humans. Extensive literature demonstrates that ghrelin, the only known orexigenic neuropeptide to date, enhances reward as well as the intake of alcohol, and other drugs of abuse, while ghrelin receptor antagonism has the opposite effects. On the other hand, the anorexigenic peptides GLP-1, amylin and NMU independently inhibits reward from alcohol and drugs of abuse in rodents. Collectively, these rodent and human studies imply that central ghrelin, GLP-1, amylin and NMU signaling may contribute to addiction processes. Therefore, the need for randomized clinical trials investigating the effects of agents targeting these aforementioned systems on drug/alcohol use is substantial.

Aetiology of eating behaviours: A possible mechanism to understand obesity development in early childhood

Childhood obesity is an issue of public health concern that is understood to emerge due to disequilibrium in energy homeostasis. This commentary explores literature regarding neuro-biological mechanisms of energy homeostasis and the relationship between subjective measures of children's eating behaviours and objective measures of appetite, in order to better understand the aetiology of childhood obesity. Early life influences, such as in utero exposure, breastfeeding, and general disadvantage, appear to have an important influence on neuro-biological mechanisms of appetite and may contribute to inequitable distributions of obesity within the population. Subject measures of eating behaviours appear to capture various aspects of neuro-biologically driven (objective) appetite systems, however, these systems are complex, interdependent and not yet fully understood. Future research focusing attention on early life influences on appetite and eating behaviours is warranted to increase understanding of differences in rates of obesity within the population, to determine opportunities for targeted obesity prevention initiatives, and to explore the potential to measure change in eating behaviours as a marker of appetite and obesity risk.

Impact of Dietary Fats on Brain Functions

BACKGROUND

Adequate dietary intake and nutritional status have important effects on brain functions and on brain health. Energy intake and specific nutrients excess or deficiency from diet differently affect cognitive processes, emotions, behaviour, neuroendocrine functions and synaptic plasticity with possible protective or detrimental effects on neuronal physiology. Lipids, in particular, play structural and functional roles in neurons. Here the importance of dietary fats and the need to understand the brain mechanisms activated by peripheral and central metabolic sensors. Thus, the manipulation of lifestyle factors such as dietary interventions may represent a successful therapeutic approach to maintain and preserve brain health along lifespan.

METHODS

This review aims at summarizing the impact of dietary fats on brain functions.

RESULTS

Starting from fat consumption, nutrient sensing and food-related reward, the impact of gut-brain communications will be discussed in brain health and disease. A specific focus will be on the impact of fats on the molecular pathways within the hypothalamus involved in the control of reproduction via the expression and the release of Gonadotropin-Releasing Hormone. Lastly, the effects of specific lipid classes such as polyunsaturated fatty acids and of the "fattest" of all diets, commonly known as "ketogenic diets", on brain functions will also be discussed.

CONCLUSION

Despite the knowledge of the molecular mechanisms is still a work in progress, the clinical relevance of the manipulation of dietary fats is well acknowledged and such manipulations are in fact currently in use for the treatment of brain diseases.

Risky decision-making after exposure to a food-choice task in excess weight adolescents: Relationships with reward-related impulsivity and hunger

OBJECTIVE

To assess the effects of exposure to a food-choice task (appetizing versus healthy food) on risky decision-making by excess versus normal weight adolescents. We also analyzed the influence of food visualization on hunger levels, as well as group differences in food choices and impulsivity.

METHODS

Fifty-six adolescents (aged 13-18 years) classified as excess (n = 27) or normal (n = 29) weight participated in the study. Risky-decision-making was assessed through the Balloon Analogue Risk Task, which was administered before and after a food-choice task. We also evaluated impulsivity traits through the UPPS-P Scale, and subjective hunger levels with a visual analogue scale.

RESULTS

Adolescents with excess weight showed enhanced risky decision-making after the food-choice task compared to normal weight adolescents, as well as increased hunger levels. Furthermore, excess weight adolescents made more appetizing choices, and showed greater scores for Positive Urgency and Sensation Seeking. Reward-related impulsivity measures were positively associated with the number of appetizing choices in the food-choice task. Several associations were found between impulsivity measures, hunger levels and risk-taking variables.

CONCLUSIONS

Excess weight adolescents increased their risky-decision-making after food exposure and this augmentation was associated with the increase in hunger levels. Increased hunger levels and risk-taking after food exposure could lead to overeating. Alterations in decision-making caused by food signals may be a long-term risk factor for the development of obesity in adulthood. In modern societies, with the high availability and continuous exposure to food cues, decision-making may be a crucial factor in maintain healthy eating habits in adolescents.

Effect of transcranial direct current stimulation associated with hypocaloric diet on weight loss and metabolic profile in overweight or obesity: study protocol for a double-blind, randomized controlled clinical trial

BACKGROUND

Dietary interventions have limited success in promoting sustainable weight loss; new treatments allowing better compliance with hypocaloric diets should be developed. The aim of this trial is to describe the effects of a protocol combining repetitive active transcranial direct current stimulation (tDCS) with a hypocaloric diet on weight loss and food consumption in overweight or obese adults.

METHODS/DESIGN

Overweight or obese adults between 20 and 50 years of age with stable weight over the last 4 months will be selected for a 4-week randomized clinical trial of fixed-dose tDCS (20 sessions; 5 consecutive weekdays/wk, 2 mA, 20 minutes) over the right dorsolateral prefrontal cortex associated with a weight loss diet. The subjects will be randomly assigned in a 1:1 ratio and stratified by sex to active tDCS + diet or sham tDCS + diet. The study will be conducted at the Endocrine and Metabolism Unit of the Hospital de Clínicas de Porto Alegre, Brazil. The primary outcome is weight loss. Energy and macronutrient consumption, as well as adherence to the diet, will be assessed using 3-day weighed dietary records. Changes in blood glucose and plasma insulin will be assessed, and participants will complete self-report questionnaires to assess changes in mood and food behavior. All analyses will be done on a per-protocol and intention-to-treat basis.

DISCUSSION

This study explores the potential role of tDCS as an adjunctive treatment with a hypocaloric diet for obesity management.

TRIAL REGISTRATION

ClinicalTrials.gov , NCT02683902 . Registered on 11 January 2016.

The effects of scheduled running wheel access on binge-like eating behavior and its consequences

Binge eating disorder (BED) is an eating disorder involving repeated, intermittent over consumption of food in brief periods of time, usually with no compensatory behaviors. There are few successful treatments and the underlying neural mechanisms remain unclear. In the current study, we hypothesized that voluntary running wheel (RW) activity could reduce binge-like eating behavior in a rat model. Rats were given intermittent (3 times/wk) limited (1hr) access to a high-fat food (Crisco), in addition to continuously available chow. Crisco was available every Mon, Wed, and Fri for 1hr before dark onset. Rats were divided into 2 groups: those with RW access during the first half of the experiment and sedentary during the second half (RW-SED) and those that were sedentary during the first half of the experiment and had RW access during the second half (SED-RW). Crisco intake was significantly less in both groups during the period of time with a RW present. Within the bingeing RW-SED rats, the gene expression of the orexigenic neuropeptides AgRP and NPY were similar to a non-bingeing sedentary control (CON) group, while the expression of the anorexigenic neuropeptide POMC was significantly increased relative to the SED-RW and CON groups. Despite elevated POMC, the rats continued to binge. Additionally, within both groups, the gene expression of the D2R and Oprm1 in the NAc and the VTA were altered suggesting that the reward system was stimulated by both the bingeing behavior and the running wheel activity. Overall, access to a RW and the resulting activity significantly reduced binge-like behavior as well as modulated the effects of binging on brain appetite and reward systems.

The effect of daily fortified yogurt consumption on weight loss in adults with metabolic syndrome: A 10-week randomized controlled trial

BACKGROUND AND AIMS

Obesity is a complex and multifaceted condition. Thus, functional foods need investigation as novel adjunct treatments for obesity. The objective was to determine the effects of daily consumption of a fortified yogurt (FY) on weight loss in overweight and obese patients with metabolic syndrome on a caloric-restricted diet.

METHODS AND RESULTS

This was a randomized, double-blind, 10-week study. Participants were randomly allocated to two groups receiving either two servings (2 × 250 g)/day of FY with whey protein, calcium, vitamin D, prebiotic fibre and probiotic cultures (n = 44) or a low-fat plain yogurt (PY) (n = 43). All participants were put on a calorie-restricted diet throughout the 10-week study. Body composition and biochemical indices were assessed before and after the intervention. Body mass decreased by 4.3 ± 1.9 kg and 5.1 ± 3.0 kg in the PY and FY groups, respectively, following the 10-week intervention. Compared to PY, consumption of FY resulted in a significant reduction in body fat mass (FM) (p = 0.023), body fat percentage (p = 0.028), waist circumference (p = 0.002), homoeostasis model of assessment-insulin resistance (HOMA-IR) (p = 0.025), triglyceride concentration (p = 0.003), and a significant increase in total 25-hydroxyvitamin D (25(OH)D) concentration (p < 0.001), high density lipoprotein-cholesterol (HDL-C) (p = 0.009) and quantitative insulin sensitivity check index (QUICKI) (0.022). Participants consuming the FY lost less fat-free mass (FFM) compared to the PY group (Δ = -0.9 ± 3.5 kg vs. Δ = -2.0 ± 2.7 kg; p = 0.025).

CONCLUSIONS

Consuming FY for 10-weeks improved body composition and metabolic parameters, while on a caloric-restricted diet. Further research is needed to elucidate whether FY can be used as a preventative strategy for metabolic syndrome in obese persons.

TRIAL REGISTRATION

www.irct.ir (IRCT2017050633836N1).

Stress, Motivation, and the Gut-Brain Axis: A Focus on the Ghrelin System and Alcohol Use Disorder

Since its discovery, the gut hormone, ghrelin, has been implicated in diverse functional roles in the central nervous system. Central and peripheral interactions between ghrelin and other hormones, including the stress-response hormone cortisol, govern complex behavioral responses to external cues and internal states. By acting at ventral tegmental area dopaminergic projections and other areas involved in reward processing, ghrelin can induce both general and directed motivation for rewards, including craving for alcohol and other alcohol-seeking behaviors. Stress-induced increases in cortisol seem to increase ghrelin in the periphery, suggesting a pathway by which ghrelin influences how stressful life events trigger motivation for rewards. However, in some states, ghrelin may be protective against the anxiogenic effects of stressors. This critical review brings together a dynamic and growing literature, that is, at times inconsistent, on the relationships between ghrelin, central reward-motivation pathways, and central and peripheral stress responses, with a special focus on its emerging role in the context of alcohol use disorder.

Cognitive and Self-regulatory Mechanisms of Obesity Study (COSMOS): Study protocol for a randomized controlled weight loss trial examining change in biomarkers, cognition, and self-regulation across two behavioral treatments

Obesity is a global epidemic, yet successful interventions are rare. Up to 60% of people fail to achieve clinically meaningful, short-term weight loss (5-10% of start weight), whereas up to 72% are unsuccessful at achieving long-term weight loss (5-10% loss for ≥5years). Understanding how biological, cognitive, and self-regulatory factors work together to promote or to impede weight loss is clearly needed to optimize obesity treatment. This paper describes the methodology of the Cognitive and Self-regulatory Mechanisms of Obesity Study (the COSMOS trial). COSMOS is the first randomized controlled trial to investigate how changes in multiple biopsychosocial and cognitive factors relate to weight loss and one another across two weight loss treatments. The specific aims are to: 1) Confirm that baseline obesity-related physiological dysregulation is linked to cognitive deficits and poorer self-regulation, 2) Evaluate pre- to post-treatment change across time to assess individual differences in biomarkers, cognition, and self-regulation, and 3) Evaluate whether the acceptance-based treatment (ABT) group has greater improvements in outcomes (e.g., greater weight loss and less weight regain, improvements in biomarkers, cognition, and self-regulation), than the standard behavioral treatment group (SBT) from pre- to post-treatment and 1-year follow-up. The results of COSMOS will provide critical information about how dysregulation in biomarkers, cognition, and/or self-regulation is related to weight loss and whether weight loss treatments are differentially associated with these factors. This information will be used to identify promising treatment targets that are informed by biological, cognitive, and self-regulatory factors in order to advance obesity treatment.

Oleoylethanolamide: The role of a bioactive lipid amide in modulating eating behaviour

Fatty acid ethanolamides are lipid mediators that regulate a plethora of physiological functions. One such bioactive lipid mediator, oleoylethanolamide (OEA), is a potent agonist of the peroxisome proliferator-activated receptor-alpha (PPAR-α), which modulates increased expression of the fatty acid translocase CD36 that enables the regulation of feeding behaviour. Consumption of dietary fat rich in oleic acid activates taste receptors in the gut activating specific enzymes that lead to the formation of OEA. OEA further combines with PPAR-α to enable fat oxidation in the liver, resulting in enhanced energy production. Evidence suggests that sustained ingestion of a high-fat diet abolishes the anorexic signal of OEA. Additionally, malfunction of the enterocyte that transforms oleic acid produced during fat digestion into OEA might be responsible for reduced satiety and hyperphagia, resulting in overweight and obesity. Thus, OEA anorectic signalling may be an essential element of the physiology and metabolic system regulating dietary fat intake and obesity. The evidence reviewed in this article indicates that intake of oleic acid, and thereby the resulting OEA imparting anorexic properties, is dependent on CD36, PPAR-α, enterocyte fat sensory receptors, histamine, oxytocin and dopamine; leading to increased fat oxidation and enhanced energy expenditure to induce satiety and increase feeding latency; and that a disruption in any of these systems will cease/curb fat-induced satiety.