Why is obesity such a problem in the 21st century? The intersection of palatable food, cues and reward pathways, stress, and cognition

Overgeneralization of autonomic defensive reactions in obesity

Generalizing defensive responses to new stimuli resembling learned threats is an adaptive process within an ever-changing environment. However, evaluation mechanisms excessively biased toward generalization (i.e., overgeneralization) may underlie anxiety-related symptoms. In the context of obesity, fear memory and fear generalization processes have never been investigated. In this study, participants with obesity and healthy participants as controls underwent a single-cue auditory fear conditioning paradigm and recognition memory tasks. We analyzed the autonomic reactions evoked by threat-predictive and new stimuli, as well as the recognition performance towards the same cues. We found that participants with obesity displayed similar autonomic defensive responses to a learned fearful stimulus, but enhanced reactions to new stimuli, when compared with the controls. We detected no significant differences between groups in recognition abilities. Our results provided the first evidence that obesity may widen fear generalization patterns. This alteration may encourage future research in investigating the link between emotional dysregulation and clinical anxiety-related symptoms in obesity.

Perineuronal nets' role in metabolism

Perineuronal nets (PNNs), specialized extracellular matrix (ECM) structures that envelop neurons, have recently been recognized as key players in the regulation of metabolism. This review explores the growing body of knowledge concerning PNNs and their role in metabolic control, drawing insights from recent research and relevant studies. The pivotal role of PNNs in the context of energy balance and whole body blood glucose is examined. This review also highlights novel findings, including the effects of astroglia, microglia, sex and gonadal hormones, nutritional regulation, circadian rhythms, and age on PNNs dynamics. These findings illuminate the complex and multifaceted role of PNNs in metabolic health.

Early Life Surgency, but not Effortful Control or Negative Affectivity, Is a Mediating Variable Between Maternal Pre-Pregnancy Body Mass Index and Childhood Obesity Risk

Maternal gestational obesity is related to risk of obesity in the child. This risk may be in part mediated by altered child temperament, which can affect mother-child interactions, including feeding and soothing behaviors that affect obesity risk. Our objective was to examine the association between maternal pre-pregnancy BMI and child zBMI and determine if child temperament, specifically positive Affectivity/Surgency, mediates this association. Using conditional process modeling, we analyzed data from 408 mother-child dyads enrolled in the Alberta Pregnancy Outcomes and Nutrition (APrON) study. Child temperament was assessed at 3 years of age via a parent report measure, the Child Behavior Questionnaire (CBQ), and child zBMI was calculated from in-person measurements of child height and weight at 4-5 years of age. Bivariate correlations showed that there was a significant positive correlation between zBMI and Surgency (r = 0.11, p = 0.03), and zBMI was also correlated with maternal pre-pregnancy BMI (r = 0.12, p = 0.02). Multivariable regression revealed that maternal pre-pregnancy BMI (adjusted β = 0.15, 95% confidence interval [CI]; 0.00-0.05, p = 0.02) and Surgency scores (adjusted β = 0.14, 95% CI; 0.02-0.28, p = 0.03) were associated with higher child zBMI at 4-5 years of age. Mediation analysis showed that Surgency mediated the association between pre-pregnancy BMI and child zBMI. Our models controlled for maternal gestational weight gain, gestational diabetes, socioeconomic status, maternal anxiety and depression, and gestational age at birth. Overall, maternal pre-pregnancy BMI was positively associated with child zBMI, and this association was mediated by higher child Surgency scores.

Monascus red pigments alleviate high-fat and high-sugar diet-induced NAFLD in mice by modulating the gut microbiota and metabolites

Monascus red pigments (MRP) may have benefits against NAFLD with an unclear mechanism. This study aimed to explore the protective effect of MRP supplementation against NAFLD through regulation of gut microbiota and metabolites. The C57BL/6 mice animals were randomly allocated into the normal diet (NC), HFHS diet-induced NAFLD model, and MRP intervention group fed with HFHS diet. Serum lipid profiles and liver function parameters were measured. Liver and colon histopathology analysis was conducted to determine the injury in the liver and colon. 16S rRNA gene sequencing was employed to analyze gut microbial composition from fecal samples. Untargeted metabonomics was performed to analyze changes in metabolites in serum and fecal samples. MRP supplementation significantly improved the HFHS-induced alterations in body weight, lipid profiles, and liver function (p < .01). MRP supplementation decreased the abundance of Akkermansia, Candidatus saccharimonas, Dubosiella, and Oscillibacter, while increasing Lactobacillus, Lachnospiraceae NK4A136 group, and Rikenella in mice fed the HFHS diet. Furthermore, MRP supplementation improved the serum and fecal metabolic profiles induced by the HFHS diet, primarily involving the arachidonic acid metabolism, unsaturated fatty acid biosynthesis, and adipocyte lipolysis pathways. Liver function and lipid profiles were closely associated with the abundance of Lactobacillus, Streptococcus, Oscillibacter, Akkemansia, and Desulfovibrio (p < .01). These findings revealed that MRP supplementation may help restore gut microbiota composition and balance its metabolites, thereby improving NAFLD. This study presents a novel outlook on the potential benefits of MRP supplementation in ameliorating NAFLD and supports the application of MRP as a new functional food.

High-fat diet and aging-associated memory impairments persist in the absence of microglia in female rats

Aging is associated with a priming of microglia such that they are hypersensitive to further immune challenges. As such high-fat diet during aging can have detrimental effects on cognition that is not seen in the young. However, conflicting findings also suggest that obesity may protect against cognitive decline during aging. Given this uncertainty we aimed here to examine the role of microglia in high-fat, high-sucrose diet (HFSD)-induced changes in cognitive performance in the aging brain. We hypothesised that 8 weeks of HFSD-feeding would alter microglia and the inflammatory milieu in aging and worsen aging-related cognitive deficits in a microglia-dependent manner. We found that both aging and HFSD reduced hippocampal neuron numbers and open field exploration; they also impaired recognition memory. However, the aging-related deficits occurred in the absence of a pro-inflammatory response and the deficits in memory performance persisted after depletion of microglia in the Cx3cr1-Dtr knock-in rat. Our data suggest that mechanisms additional to the acute microglial contribution play a role in aging- and HFSD-associated memory dysfunction.

A shift to a standard diet after exposure to a high-fat, high-sucrose diet from gestation to weaning restores brain metabolism and behavioral flexibility in adult rats

Prolonged consumption of diets high in saturated fat and sugar has been related to obesity and overweight, which in turn are linked to cognitive impairment in both humans and rodents. This has become a current issue, especially in children and adolescents, because these stages are crucial to neurodevelopmental processes and programming of adult behavior. To evaluate the effects of gestational and early exposure to an obesogenic diet, three groups with different dietary patterns were established: high-fat and high-sucrose diet (HFS), standard diet (SD), and a dietary shift from a high-fat, high-sucrose diet to a standard diet after weaning (R). Spatial learning and behavioral flexibility in adult male and female Wistar rats were evaluated using the Morris water maze (MWM) at PND 60. Furthermore, regional brain oxidative metabolism was assessed in the prefrontal cortex and the hippocampus. Contrary to our hypothesis, the HFS diet groups showed similar performance on the spatial learning task as the other groups, although they showed impaired cognitive flexibility. The HFS group had increased brain metabolic capacity compared to that of animals fed the standard diet. Shifting from the HFS diet to the SD diet after weaning restored the brain metabolic capacity in both sexes to levels similar to those observed in animals fed the SD diet. In addition, animals in the R group performed similarly to those fed the SD diet in the Morris water maze in both tasks. However, dietary shift from HFS diet to standard diet after weaning had only moderate sex-dependent effects on body weight and fat distribution. In conclusion, switching from an HFS diet to a balanced diet after weaning would have beneficial effects on behavioral flexibility and brain metabolism, without significant sex differences.

The different areas of chronic stress and food addiction: Results from the LIFE-Adult-Study

There is an empirical association between stress and symptoms of food addiction (FA), but it is still not clear which domains of stress are the most relevant when it comes to FA, limiting the ability of researchers and practitioners to address problematic eating-related health outcomes. In order to address this gap in the literature, we analysed how different domains of chronic stress are related to FA. We used data from a subsample of the LIFE-Adult-Study (N = 1172), a German cohort study. We conducted a linear regression analysis with stress domains (Trier Inventory for Chronic Stress, TICS) as predictors of FA (Yale Food Addiction Scale, YFAS). In the second regression analysis we included sociodemographic variables, personality, and smoking as control variables. There was a significant and positive association between Social Overload, Work Discontent, Excessive Demands from Work, and Chronic Worrying and FA. After adding control variables, only Social Overload, Excessive Demands from Work, and Chronic Worrying remained significant predictors. Connections between stress domains and FA can serve as starting points for the development of meaningful interventions that support individuals self-care strategies (Social Overload), complexity management (Excessive Demands from Work), and coping with negative emotions (Chronic Worrying).

Defining a vitamin A5/X specific deficiency - vitamin A5/X as a critical dietary factor for mental health

A healthy and balanced diet is an important factor to assure a good functioning of the central and peripheral nervous system. Retinoid X receptor (RXR)-mediated signaling was identified as an important mechanism of transmitting major diet-dependent physiological and nutritional signaling such as the control of myelination and dopamine signalling. Recently, vitamin A5/X, mainly present in vegetables as provitamin A5/X, was identified as a new concept of a vitamin which functions as the nutritional precursor for enabling RXR-mediated signaling. The active form of vitamin A5/X, 9-cis-13,14-dehydroretinoic acid (9CDHRA), induces RXR-activation, thereby acting as the central switch for enabling various heterodimer-RXR-signaling cascades involving various partner heterodimers like the fatty acid and eicosanoid receptors/peroxisome proliferator-activated receptors (PPARs), the cholesterol receptors/liver X receptors (LXRs), the vitamin D receptor (VDR), and the vitamin A(1) receptors/retinoic acid receptors (RARs). Thus, nutritional supply of vitamin A5/X might be a general nutritional-dependent switch for enabling this large cascade of hormonal signaling pathways and thus appears important to guarantee an overall organism homeostasis. RXR-mediated signaling was shown to be dependent on vitamin A5/X with direct effects for beneficial physiological and neuro-protective functions mediated systemically or directly in the brain. In summary, through control of dopamine signaling, amyloid β-clearance, neuro-protection and neuro-inflammation, the vitamin A5/X - RXR - RAR - vitamin A(1)-signaling might be "one of" or even "the" critical factor(s) necessary for good mental health, healthy brain aging, as well as for preventing drug addiction and prevention of a large array of nervous system diseases. Likewise, vitamin A5/X - RXR - non-RAR-dependent signaling relevant for myelination/re-myelination and phagocytosis/brain cleanup will contribute to such regulations too. In this review we discuss the basic scientific background, logical connections and nutritional/pharmacological expert recommendations for the nervous system especially considering the ageing brain.

The effects of paternal dietary fat versus sugar on offspring body composition and anxiety-related behavior

Increasing evidence suggests that the pre-conception parental environment has long-term consequences for offspring health and disease susceptibility. Though much of the work in this field concentrates on maternal influences, there is growing understanding that fathers also play a significant role in affecting offspring phenotypes. In this study, we investigate effects of altering the proportion of dietary fats and carbohydrates on paternal and offspring body composition and anxiety-related behavior in C57Bl/6-JArc mice. We show that in an isocaloric context, greater dietary fat increased body fat and reduced anxiety-like behavior of studs, whereas increased dietary sucrose had no significant effect. These dietary effects were not reflected in offspring traits, rather, we found sex-specific effects that differed between offspring body composition and behavioral traits. This finding is consistent with past paternal effect studies, where transgenerational effects have been shown to be more prominent in one sex over the other. Here, male offspring of fathers fed high-fat diets were heavier at 10 weeks of age due to increased lean body mass, whereas paternal diet had no significant effect on female offspring body fat or lean mass. In contrast, paternal dietary sugar appeared to have the strongest effects on male offspring behavior, with male offspring of high-sucrose fathers spending less time in the closed arms of the elevated plus maze. Both high-fat and high-sugar paternal diets were found to reduce anxiety-like behavior of female offspring, although this effect was only evident when offspring were fed a control diet. This study provides new understanding of the ways in which diet can shape the behavior of fathers and their offspring and contribute to the development of dietary guidelines to improve obesity and mental health conditions, such as anxiety.

Changes in reward-induced neural activity upon Cafeteria Diet consumption

Excessive consumption of highly palatable foods rich in sugar and fat, often referred to as "junk" or "fast" foods, plays a central role in the development of obesity. The highly palatable characteristics of these foods activate hedonic and motivational mechanisms to promote food-seeking behavior and overeating, which is largely regulated by the brain reward system. Excessive junk food consumption can alter the functioning of this reward system, but exact mechanisms of these changes are still largely unknown. This study investigated whether long-term junk food consumption, in the form of Cafeteria (CAF) diet, can alter the reward system in adult, female Long-Evans rats, and whether different regimes of CAF diet influence the extent of these changes. To this end, rats were exposed to a 6-week diet with either standard chow, or ad libitum daily access to CAF diet, 30 % restricted but daily access to CAF diet, or one-day-a-week (intermittent) ad libitum access to CAF diet, after which c-Fos expression in the Nucleus Accumbens (NAc), Prefrontal Cortex (PFC), and Ventral Tegmental Area (VTA) following consumption of a CAF reward of choice was examined. We found that all CAF diet regimes decreased c-Fos expression in the NAc-shell when presented with a CAF reward, while no changes in c-Fos expression upon the different diet regimes were found in the PFC, and possibly the VTA. Our data suggests that long-term junk food exposure can affect the brain reward system, resulting in an attenuated activity of the NAc-shell.

Measuring Pleasure from Food-Validation of the Food Pleasure Scale by Multiple Techniques and Mixed Methods

The development of scales and questionnaires to assess pleasure perception has gained prominence, particularly for evaluating anhedonia in mental disorders. The Food Pleasure Scale is a comprehensive tool exclusively dedicated to measuring pleasure perception from food and food-related experiences. This study aimed to evaluate the face validity and consistency reliability of the Food Pleasure Scale using a mixed methods approach. Twenty-two participants completed the Food Pleasure Scale questionnaire and participated in in-depth interviews to understand their interpretation of the scale items. The interview data underwent thematic analysis, and the quantitative survey data was compared to the qualitative interview responses. Results indicated a high level of understanding of all items in the Food Pleasure Scale, confirming its face validity and applicability. The mixed methods approach supported the consistency reliability, showing consistency between quantitative measures and participants' explicit and implicit expressions of food pleasure. Furthermore, the study revealed a novel aspect related to food pleasure: the concept of "making an effort". Overall, this study highlights the comprehensibility, validity, and potential of the Food Pleasure Scale in consumer studies. It effectively captures the subjective experience of pleasure derived from food and food-related encounters, making it a valuable tool for further research in this domain.

Effects of NKT Cells on Metabolic Disorders Caused by High-Fat Diet Using CD1d-Knockout Mice

Purpose

The purpose of this study was to investigate whether NKT cells play an important role in preventing or exacerbating diseases caused by high-fat diet (HFD) using CD1d-knockout (KO) mice which lack NKT cells.

Methods

Five-week-old male Balb/c (wild-type; WT) or CD1dKO mice were fed with control-diet (CTD) or HFD for 16 weeks.

Results

The present study revealed four main findings. First, CD1dKO mice were susceptible to obesity caused by HFD in comparison to WT mice. Second, clinical conditions of fatty liver caused by HFD were comparable between CD1dKO mice and WT mice. Third, HFD-fed WT mice showed high levels of serum biochemical markers, involved in lipid metabolisms, in comparison to WT mice fed a CTD. Notably, the serum concentrations of ALT, T-CHO, TG and HDL-C in CD1dKO mice fed a HFD were almost comparable to those of CD1dKO mice fed a CTD. Fourth, the expression of peroxisome proliferator-activated receptor (PPAR) γ, low-density lipoprotein receptor (LDLR), CD36 of epididymal adipose tissue enhanced and proprotein convertase subtilisin/kexin type (PCSK) 9 in serum decreased.

Conclusion

NKT cells were responsible for protection against HFD-induced obesity. However, CD1dKO mice were resistant to serum biochemical marker abnormalities after HFD feeding. One possible explanation is that the epididymal adipose tissue of CD1dKO mice could take up greater amounts of excess lipids in serum in comparison to WT mice.

Microbes, oxytocin and stress: Converging players regulating eating behavior

Oxytocin is a peptide-hormone extensively studied for its multifaceted biological functions and has recently gained attention for its role in eating behavior, through its action as an anorexigenic neuropeptide. Moreover, the gut microbiota is involved in oxytocinergic signaling through the brain-gut axis, specifically in the regulation of social behavior. The gut microbiota is also implicated in appetite regulation and is postulated to play a role in central regulation of hedonic eating. In this review, we provide an overview on oxytocin and its individual links with the microbiome, the homeostatic and non-homeostatic regulation of eating behavior as well as social behavior and stress.

Technology and functional insights into the nicotinamide mononucleotide for human health

Nicotinamide mononucleotide (NMN), a naturally occurring biologically active nucleotide, mainly functions via mediating the biosynthesis of NAD⁺. In recent years, its excellent pharmacological activities including anti-aging, treating neurodegenerative diseases, and protecting the heart have attracted increasing attention from scholars and entrepreneurs for production of a wide range of formulations, including functional food ingredients, health care products, active pharmaceuticals, and pharmaceutical intermediates. Presently, the synthesis methods of NMN mainly include two categories: chemical synthesis and biosynthesis. With the development of biocatalyst engineering and synthetic biology strategies, bio-preparation has proven to be efficient, economical, and sustainable methods. This review summarizes the chemical synthesis and biosynthetic pathways of NMN and provides an in-depth investigation on the mining and modification of enzyme resources during NMN biosynthesis, as well as the screening of hosts and optimization of chassis cells via metabolic engineering, which provide effective strategies for efficient production of NMN. In addition, an overview of the significant physiological functions and activities of NMN is elaborated. Finally, future research on technical approaches to further enhance NMN synthesis and strengthen clinical studies of NMN are prospected, which would lay the foundation for further promoting the application of NMN in nutrition, healthy food, and medicine in the future. KEY POINTS: • NMN supplementation effectively increases the level of NAD⁺. • The chemical and biological synthesis of NMN are comprehensively reviewed. • The impact of NMN on the treatment of various diseases is summarized.

Behavioral, cognitive, and socioemotional pathways from early childhood adversity to BMI: Evidence from two prospective, longitudinal studies

Childhood adversity is associated with higher adult weight, but few investigations prospectively test mechanisms accounting for this association. Using two socioeconomically high-risk prospective longitudinal investigations, the Minnesota Longitudinal Study of Risk and Adaptation (MLSRA; N = 267; 45.3% female) and the Fragile Families and Child Wellbeing Study (FFCWS; n = 2,587; 48.5% female), pathways between childhood adversity and later body mass index (BMI) were tested using impulsivity, emotion dysregulation, and overeating as mediators. Childhood adversity from 0 to 5 years included four types of adversities: greater unpredictability, threat/abuse, deprivation/neglect, and low socioeconomic status. Parents reported on child impulsivity, emotion dysregulation, and overeating. Height and weight were self-reported and measured at 32 and 37 years in MLSRA and at 15 years in FFCWS. FFCWS results indicated that threat, deprivation, and low socioeconomic status predicted greater impulsivity and emotion dysregulation at 5 years, which in turn predicted greater overeating at 9 years and higher BMI z-score at 15 years. Early unpredictability in FFCWS predicted higher BMI through greater impulsivity but not emotion dysregulation at age 5. MLSRA regression results replicated the threat/abuse → emotion dysregulation → overeating → higher BMI pathway. These findings suggest that different dimensions of early adversity may follow both similar and unique pathways to predict BMI.

Addiction-like behaviour towards high-fat high-sugar food predicts relapse propensity in both obesity prone and obesity resistant C57BL/6 J mice

Compulsive overeating of palatable food is thought to underlie some forms of obesity. Similarities are often observed in the behavioural symptomology and the neuropathophysiology underlying substance use disorder and compulsive overeating. As such, preclinical animal models which assess addiction-like behaviour towards food may assist the understanding of the neurobiology underlying overeating behaviour. Further, the relationship between these behaviours and the propensity for diet-induced obesity warrants examination. In this study we investigated the relationship between the propensity for diet-induced obesity (DIO) and addiction-like behaviour towards highly palatable food in C57BL/6 J mice as measured by a 3-criteria model. We also examined the extent to which performance on this 3-criteria model predicted two key hallmark features of addiction - resistance to extinction and relapse propensity (as measured by reinstatement of lever pressing). C57BL/6 J mice were allowed free access to a palatable diet for 8 weeks then separated by weight gain into DIO-prone and DIO-resistant subgroups. Access to palatable food was then restricted to daily operant self-administration sessions whereby addiction-like behaviour towards a high-fat high-sugar food reward was assessed using a 3-criteria model similar to that used to assess addiction-like behaviour towards drugs of abuse. In contrast to findings in rats, no difference in addiction-like behaviour towards food was observed between obesity prone (OP) and obesity resistant (OR) mice. Similarly, principal components analysis found no distinct patterns in the relationship between addiction-like behaviours across treatment groups. This suggests that the strain and species of rodent may be critical for studying the mechanisms underlying pathological overconsumption. Further analysis revealed that the extent of performance on the 3-criteria model correlated with the propensity for C57BL/6 J mice to both extinguish food seeking behaviour and "relapse" after a period of withdrawal. This finding was evident across all groups, regardless of DIO. Collectively, these data validate the 3-criteria model as a robust model to comprehensively assess food addiction-like behaviour in mice, regardless of prior food intake history.

Perceived Stress Is Directly Associated with Major Consumption of Sugar-Sweetened Beverages among Public University Students

Stress is a condition that has been related to the development of risk behaviors for health such as sugar-sweetened beverages (SSBs) consumption. The aim of this study was to examine the link between SSBs consumption and perceived stress level in university students. This was an observational, cross-sectional and single-time-point study where the subjects were recruited as a non-probabilistic sample of first-year university students. The students reported their SSBs consumption through a validated questionnaire, as well as their perceived stress level, evaluated through the Cohen scale. Comparisons were made between the means of all variables. Factorial analysis of variance was conducted to explore the effect of the variables’ interaction on the stress level. One-way analysis of variance was performed to assess differences between the sexes. Men consumed more SSBs (6101.17 ± 3772.50 mL/week) compared to women (4294.06 ± 3093.8 mL/week). However, women had higher scores of perceived stress and showed a strong association of stress with the SSBs consumption pattern (r and p-value). This study shows for the first time the association that exists between stress and SSBs consumption and indicates that it is related to sex in the young population.

Effects of the healthy lifestyle community program (cohort 1) on stress-eating and weight change after 8 weeks: a controlled study

Stress-eating (eating more or more unhealthily in order to accommodate to stress), contributes to the development and maintenance of obesity. The effect of comprehensive weight loss interventions on changes in stress-eating as well as the contributing role of stress-eating on weight reduction has not been examined. The impact of the 8-week intensive phase of the Healthy Lifestyle Community Programme (HLCP, cohort 1) on emotional, external and restrained eating, as expressions of stress-eating was evaluated in a non-randomized controlled trial. Intervention: 14 seminars (twice per week, including practical units), complemented by stress-regulation and cooking workshops and coaching sessions empowering participants to change their behaviour towards a healthy plant-based diet (ad libitum), stress regulation, regular exercise and to focus on social support. Participants were recruited from the general population. In the intervention group, 91 participants (IG; age: 56 ± 10, 77% female) and in the control group, 52 (CG; age: 62 ± 14, 57% female) were enrolled. At baseline, participants of the IG reported higher levels of stress (9.7 ± 5.4 points [P] vs. 7.6 ± 6.2; p < 0.011), and of emotional eating (27.9 ± 9.4 vs. 20.0 ± 7.1; p < 0.001) and external eating (29.1 ± 4.9 vs. 25.5 ± 5.6; p < 0.001) than participants of the CG. Within 8 weeks, in the IG, scores of emotional eating (- 3.5 ± 5.4 P) and external eating significantly decreased (= - 2.0 ± 3.8 P), while restrained eating increased (2.7 ± 5.0 P; p for all < 0.001). Weight change was negatively correlated with change of external eating (R2 = 0.045; CC = - 0.285; p = 0.014), indicating that a greater weight change was associated with a smaller change of external eating. This is the first study to prospectively investigate the role of stress-eating on the weight reduction effect of comprehensive lifestyle interventions. Our data confirm that overweight is associated with EE and external eating and suggest that the HLCP is capable to reduce both, weight and stress-eating.Trial registration: German Clinical Trials Register (DRKS; reference: DRKS00018821; September 18th 2019; retrospectively registered).

Hyperpalatable Foods Consumption in a Representative Sample of the General Population in Brazil: Differences of Binge and Non-Binge Eating Meals

The availability of hyper-palatable foods (HPF) increased over the past three decades worldwide, a period when eating disorders (ED) and obesity have become global public health concerns. The present study aimed to assess HPF consumption during binge and non-binge meals in a representative sample of adults with and without ED from a metropolitan city in Brazil. A total of 2297 individuals were interviewed in their homes by trained lay interviewers to assess the presence of binge eating disorder (BED), bulimia nervosa (BN), and recurrent binge eating (RBE). Information on their food consumption in objective and subjective binge eating episodes (OBE and SBE, respectively), as well as in the 24 h food recall were obtained. Individuals from the general population consumed 56% of their total calories from HPF. In non-binge meals, people with BN consumed substantially fewer calories from HPF than BED (63% vs. 48%) and RBE (63% vs. 48%) groups. During OBE, participants consumed an average of 70% of the calories from HPF, with no between-group differences. During SBE, subjects with BN consumed substantially fewer calories from HPF than those with BED (76% vs. 50%). In conclusion, HPF were highly consumed by the Brazilian population. However, there was a greater impact on BED and RBE subjects and during binge eating episodes.

Net gain and loss: influence of natural rewards and drugs of abuse on perineuronal nets

Overindulgence, excessive consumption, and a pattern of compulsive use of natural rewards, such as certain foods or drugs of abuse, may result in the development of obesity or substance use disorder, respectively. Natural rewards and drugs of abuse can trigger similar changes in the neurobiological substrates that drive food- and drug-seeking behaviors. This review examines the impact natural rewards and drugs of abuse have on perineuronal nets (PNNs). PNNs are specialized extracellular matrix structures that ensheathe certain neurons during development over the critical period to provide synaptic stabilization and a protective microenvironment for the cells they surround. This review also analyzes how natural rewards and drugs of abuse impact the density and maturation of PNNs within reward-associated circuitry of the brain, which may contribute to maladaptive food- and drug-seeking behaviors. Finally, we evaluate the relatively few studies that have degraded PNNs to perturb reward-seeking behaviors. Taken together, this review sheds light on the complex way PNNs are regulated by natural rewards and drugs and highlights a need for future studies to delineate the molecular mechanisms that underlie the modification and maintenance of PNNs following exposure to rewarding stimuli.

Development of Chinese food picture library for inducing food cravings

Cue-induced food cravings are strong desires directed toward specific foods, usually ones with high caloric content, and can lead to overeating. However, although food cravings vary according to individual preferences for specific high-calorie food subtypes, a structured library of food craving-inducing pictures including multiple categories of high-calorie foods does not yet exist. Here, we developed and validated a picture library of Chinese foods (PLCF) consisting of five subtypes of high-calorie foods (i.e., sweets, starches, salty foods, fatty foods, and sugary drinks) to allow for more nuanced future investigations in food craving research, particularly in Chinese cultural contexts. We collected 100 food images representing these five subtypes, with four food items per subtype depicted in five high-resolution photographs each. We recruited 241 individuals with overweight or obesity to rate the food pictures based on craving, familiarity, valence, and arousal dimensions. Of these participants, 213 reported the severity of problematic eating behaviors as a clinical characteristic. Under the condition of mixing multiple subtypes of high-calorie foods, we did not observe significant differences in craving ratings for high- and low-calorie food images (p _tukey > 0.05). Then, we compared each subtype of high-calorie food images to low-calorie ones, and found craving ratings were greater for the images of salty foods and sugary drinks (ps < 0.05). Furthermore, we conducted a subgroup analysis of individuals according to whether they did or did not meet the criteria for food addiction (FA) and found that greater cravings induced by the images of high-calorie food subtypes (i.e., salty foods and sugary drinks) only appeared in the subgroup that met the FA criteria. The results show that the PLCF is practical for investigating food cravings.

Impact of Calorie-Restricted Cafeteria Diet and Treadmill Exercise on Sweet Taste in Diet-Induced Obese Female and Male Rats

The goal of the present study was to evaluate the sweet taste function in obese rats fed with a 30% calorie-restricted cafeteria diet (CAFR) and/or subjected to moderate treadmill exercise (12-17 m/min, 35 min, 5 days per week) for 9 weeks. A two-bottle preference test, a taste reactivity test, and a brief-access licking test were carried out when animals were aged 21 weeks; biometric and metabolic parameters were also measured along the interventions. Two separate experiments for females and males were performed. Behaviorally, CAF diet decreased sucrose intake and preference, as well as perceived palatability, in both sexes and decreased hedonic responses in males. Compared to the CAF diet, CAFR exerted a corrective effect on sweet taste variables in females by increasing sucrose intake in the preference test and licking responses, while exercise decreased sucrose intake in both sexes and licking responses in females. As expected, CAF diet increased body weight and Lee index and worsened the metabolic profile in both sexes, whereas CAFR diet ameliorated these effects mainly in females. Exercise had no noticeable effects on these parameters. We conclude that CAF diet might diminish appetitive behavior toward sucrose in both sexes, and that this effect could be partially reverted by CAFR diet in females only, while exercise might exert protective effects against overconsumption of sucrose in both sexes.

Sexual dimorphism in spatial learning and brain metabolism after exposure to a western diet and early life stress in rats

Prolonged daily intake of Western-type diet rich in saturated fats and sugars, and exposure to early life stress have been independently linked to impaired neurodevelopment and behaviour in animal models. However, sex-specific effects of both environmental factors combined on spatial learning and memory, behavioural flexibility, and brain oxidative capacity have still not been addressed. The current study aimed to evaluate the impact of maternal and postnatal exposure to a high-fat and high-sugar diet (HFS), and exposure to early life stress by maternal separation in adult male and female Wistar rats. For this purpose, spatial learning and memory and behavioural flexibility were evaluated in the Morris water maze, and regional brain oxidative capacity and oxidative stress levels were measured in the hippocampus and medial prefrontal cortex. Spatial memory, regional brain oxidative metabolism, and levels of oxidative stress differed between females and males, suggesting sexual dimorphism in the effects of a HFS diet and early life stress. Males fed the HFS diet performed better than all other experimental groups independently of early life stress exposure. However, behavioural flexibility evaluated in the spatial reversal leaning task was impaired in males fed the HFS diet. In addition, exposure to maternal separation or the HFS diet increased the metabolic capacity of the prefrontal cortex and dorsal hippocampus in males and females. Levels of oxidative stress measured in the latter brain regions were also increased in groups fed the HFS diet, but maternal separation seemed to dampen regional brain oxidative stress levels. Therefore, these results suggest a compensatory effect resulting from the interaction between prolonged exposure to a HFS diet and early life stress.

Snacking for a reason: detangling effects of socio-economic position and stress on snacking behaviour

BACKGROUND

As snacking can be considered a cornerstone of an unhealthy diet, investigating psychological drivers of snacking behaviour is urgent, and therefore the purpose of this study. Socio-economic position (SEP) and stress are known to affect many behaviours and outcomes, and were therefore focal points in the study.

METHODS

In a cross-sectional survey study, we examined whether Socio-economic position (SEP) would amplify associations between heightened stress levels and self-reported negative-affect related reasons for snacking. Next, we investigated whether Socio-economic position (SEP) predicted frequency of snacking behaviour, and how stress and other reasons for snacking could explain this association. Outcome measures were reasons people indicated for snacking, and frequency of snacking behaviour.

RESULTS

Analyses revealed that people seem to find more reasons to snack when they are stressed, and that this association was more pronounced for people with a high compared to low socio-economic position. Furthermore, a higher socio-economic position was associated with a higher frequency of snacking, and both snacking to reward oneself and snacking because of the opportunity to do so remained significant mediators.

CONCLUSION

Whereas low socio-economic position was associated with higher stress levels, this did not translate into increased snacking. Contrarily, those with higher socio-economic position could be more prone to using 'reasons to snack', which may result in justification of unhealthy snacking behaviour.

The effects of an obesogenic diet on behavior and cognition in zebrafish (Danio rerio): Trait average, variability, repeatability, and behavioral syndromes

The obesity epidemic, largely driven by the accessibility of ultra-processed high-energy foods, is one of the most pressing public health challenges of the 21st century. Consequently, there is increasing concern about the impacts of diet-induced obesity on behavior and cognition. While research on this matter continues, to date, no study has explicitly investigated the effect of obesogenic diet on variance and covariance (correlation) in behavioral traits. Here, we examined how an obesogenic versus control diet impacts means and (co-)variances of traits associated with body condition, behavior, and cognition in a laboratory population of ~160 adult zebrafish (Danio rerio). Overall, an obesogenic diet increased variation in several zebrafish traits. Zebrafish on an obesogenic diet were significantly heavier and displayed higher body weight variability; fasting blood glucose levels were similar between control and treatment zebrafish. During behavioral assays, zebrafish on the obesogenic diet displayed more exploratory behavior and were less reactive to video stimuli with conspecifics during a personality test, but these significant differences were sex-specific. Zebrafish on an obesogenic diet also displayed repeatable responses in aversive learning tests whereas control zebrafish did not, suggesting an obesogenic diet resulted in more consistent, yet impaired, behavioral responses. Where behavioral syndromes existed (inter-class correlations between personality traits), they did not differ between obesogenic and control zebrafish groups. By integrating a multifaceted, holistic approach that incorporates components of (co-)variances, future studies will greatly benefit by quantifying neglected dimensions of obesogenic diets on behavioral changes.

Associations Between Food Addiction and Substance-Use Disorders: A Critical Overview of their Overlapping Patterns of Consumption

Purpose of Review

Research on patterns of overconsumption in individuals with food addiction (FA) has focused largely on binge eating. However, compulsive overeating can be varied and dimensional. This review focuses on the similarities between the patterns of consumption in FA and in other clinically established substance-use disorders, such as alcohol and nicotine dependence. It also highlights features that make FA unique to other addiction disorders.

Recent Findings

Overall, there is substantial evidence that binge-like overconsumption is a characteristic of various substance-use and eating disorders. Likewise, it appears that different overeating patterns can reflect addictive-like eating. One pattern may be compulsive grazing — defined as the repetitive inability to resist consumption of small amounts of food.

Summary

This review adds to the increasingly compelling picture that FA and binge-eating disorder are unique conditions, and that FA resembles other substance-use disorders. We conclude that a variety of overeating patterns can reflect addictive eating behaviours in vulnerable individuals, one of which may be compulsive grazing.

Dietary and Nutritional Profiles among Brazilian Adolescents

(1) Background: The present study analyzed the prevalence of dietary and nutritional profiles among Brazilian adolescents and their associations with social determinants of health. (2) Methods: A population-based survey was administered to 16,409 adolescents assessed by the 2015 National School Health Survey. A multivariate model of dietary and nutritional profiles was estimated from correspondence analysis. (3) Results: The dietary and nutritional profiles more prevalent among Brazilian adolescents were “lower nutritional risk dietary pattern and eutrophic” (42.6%), “lower nutritional risk dietary pattern and overweight” (6.8%), and “higher nutritional risk dietary pattern and overweight” (6.0%). Healthier profiles were associated with less urbanized territories, health-promoting behaviors, and families with worse material circumstances. The less healthy profiles were associated with more urbanized environments, health risk behaviors, and families with better material circumstances. (4) Brazilian adolescents have different dietary and nutritional profiles that are characterized by sociopolitical and economic contexts, family material and school circumstances, and the behavioral and psychosocial health factors of the individuals. All of this points to the social determination of these health problems among adolescents in Brazil.

IL10/AMPK pathway was associated with the hippocampal anti-inflammatory response to high-sugar and high-fat diet withdrawal

OBJECTIVE

The present experimental study aimed to evaluate the effect of consuming an obesogenic diet (OD) on serum and hippocampal inflammation and proteins related to energy metabolism, alongside, we evaluated how the same parameters responded to an OD withdrawal.

SUBJECTS

Thirty male 60-days-old Wistar rats were used.

METHODS

The control group (n = 10) was fed the control diet across the whole experiment. The remaining animals were fed a high-sugar/high-fat (HSHF) diet for 30 days (n = 20) and half of them were placed on the control diet for 48 h (n = 10) afterwards.

RESULTS

OD intake decreased hippocampal AMPK phosphorylation, although, it did not increase serum inflammation and only increased hippocampal pNFκBp65 levels without any increase in the cytokines assessed. Moreover, OD withdrawal led to higher inflammatory markers in the serum and hippocampus and higher hippocampal AMPK phosphorylation. The mediation models applied suggested that the effect of OD withdrawal on hippocampal inflammation was driven by serum inflammation, which activated the hippocampal IL10/AMPK anti-inflammatory pathway as a response.

CONCLUSION

Our analyses suggest that OD withdrawal increases serum inflammation with hippocampal consequent inflammatory alterations. Despite the general assumption that improving diet improves health, this may not be immediate.

Hippocampal BDNF mediated anxiety-like behaviours induced by obesogenic diet withdrawal

Obesogenic diets (ODs) consumption is associated with anxiety-like behaviour and negative changes in hippocampal BDNF. At the same time, interrupting OD intake, OD withdrawal (WTD), can bring health benefits, but previous studies reported the development of anxiety-like behaviours. The present work aimed to assess the relationship between anxiety-like behaviour with hippocampal BDNF in a WTD rodent model. Male Wistar rats (60d old) were fed a high-sugar/high-fat (HSHF) diet for 30d (n=32), and half of them were transitioned to a control diet for 48h (n=16) afterwards. The control group (n=16) was fed a control diet across the whole experiment. Besides increasing anxiety-like behaviours and lowering sociability, the WTD led to an increase in BDNF in the dentate gyrus and the CA1 of the hippocampus. It also decreased locomotor activity in both OF and EPM, however, they did not significantly interfere with the other behavioural parameters analysed. Western blotting analysis revealed that the increase in BDNF likely occurred in the mature forms (14kD monomer and 28kD dimer). The mediation models analyses suggested that the effect of WTD on anxiety-like behaviour was driven by hippocampal BDNF, this mediation of effect was region-dependent. Our results also suggested that mature BDNF forms (14kD and 28kD) were responsible. The present work brought light to a possible new role for mature BDNF, although it is generally associated with beneficial features, it can also be part of the genesis of anxiety-like behaviours and sociability aspects on WTD models.

Neurobiological Mechanisms Modulating Emotionality, Cognition and Reward-Related Behaviour in High-Fat Diet-Fed Rodents

Affective and substance-use disorders are associated with overweight and obesity-related complications, which are often due to the overconsumption of palatable food. Both high-fat diets (HFDs) and psychostimulant drugs modulate the neuro-circuitry regulating emotional processing and metabolic functions. However, it is not known how they interact at the behavioural level, and whether they lead to overlapping changes in neurobiological endpoints. In this literature review, we describe the impact of HFDs on emotionality, cognition, and reward-related behaviour in rodents. We also outline the effects of HFD on brain metabolism and plasticity involving mitochondria. Moreover, the possible overlap of the neurobiological mechanisms produced by HFDs and psychostimulants is discussed. Our in-depth analysis of published results revealed that HFDs have a clear impact on behaviour and underlying brain processes, which are largely dependent on the developmental period. However, apart from the studies investigating maternal exposure to HFDs, most of the published results involve only male rodents. Future research should also examine the biological impact of HFDs in female rodents. Further knowledge about the molecular mechanisms linking stress and obesity is a crucial requirement of translational research and using rodent models can significantly advance the important search for risk-related biomarkers and the development of clinical intervention strategies.

Is Stress Taking the Pleasure out of Food?—A Characterization of the Food Pleasure Profiles, Appetite, and Eating Behaviors of People with Chronic Stress

Psychological stressors frequently occur in modern society, and are associated with general anhedonic traits (inability to experience pleasure) and altered eating behavior. As eating behavior is largely motivated by a desire for pleasure, the Food Pleasure Scale (FPS) was introduced as a new research tool for investigating aspects of pleasure from food-related experiences. Thereby, insights on whether some aspects of pleasure are more affected by stress than others can be investigated, and can help explain why changes in eating behavior are seen when under the influence of stress. A consumer survey including n = 190 Danish consumers all with moderate or high levels of perceived stress was conducted to explore the perception of pleasure from food, general appetite, meal patterns, as well as specific food preferences. The study showed that the majority found pleasure in the sensory modalities of food, as well as in the ‘comforting’ aspects of food pleasure. Furthermore, the moderately stressed respondents had fewer main meals and more post-dinner snacks and night meals, as compared to before falling ill, whereas the highly stressed group showed signs of anhedonic traits and losing appetite altogether. The present study contributes to our understanding of how a common condition, such as chronic stress, can affect individual, as well as public, health.

Cognitive profile of male mice exposed to a Ketogenic Diet

In recent years, nutritional interventions for different psychiatric diseases have gained increasing attention, such as the ketogenic diet (KD). This has led to positive effects in neurological disorders such as Parkinson's disease, addiction, autism or epilepsy. The neurobiological mechanisms through which these effects are induced and the effects in cognition still warrant investigation, and considering that other high-fat diets (HFD) can lead to cognitive disturbances that may affect the results achieved, the main aim of the present work was to evaluate the effects of a KD to determine whether it can induce such cognitive effects. A total of 30 OF1 male mice were employed to establish the behavioral profile of mice fed a KD by testing anxiety behavior (Elevated Plus Maze), locomotor activity (Open Field), learning (Hebb Williams Maze), and memory (Passive Avoidance Test). The results revealed that the KD did not affect locomotor activity, memory or hippocampal-dependent learning, as similar results were obtained with mice on a standard diet, albeit with increased anxiety behavior. We conclude that a KD is a promising nutritional approach to apply in research studies, given that it does not cause cognitive alterations.

Why Being 'Stressed' Is 'Desserts' in Reverse-The Effect of Acute Psychosocial Stress on Food Pleasure and Food Choice

The link between acute stress, food pleasure and eating behavior in humans by employing measures of individual reward mechanisms has not been investigated as of yet. Having these insights is key to understanding why many people experience a change in eating behavior when experiencing stress. Thirty-five Danes (mean age 21.71 years) underwent a stress-inducing and relaxation-inducing task based on a randomized cross-over study design. Both tasks were combined with the Leeds Food Preference Questionnaire, to investigate the effect of stress on specific measures of food reward. Furthermore, participants chose a snack, as a covert measure of actual food choice. The study found no effect on explicit liking, explicit wanting or relative preference. For implicit wanting, an effect was detected on high-fat sweet foods, with increasing scores for the stress-induced condition. Moreover, 54% chose a different snack following the stress-inducing condition. Interestingly, 14% chose to change their snack choice to no snack at all. Results suggest acute psychosocial stress can increase cravings for highly palatable foods for some, while for others an experience of loss of appetite prevails. Overall, this study points to a further understanding of why consumers have issues with making healthy food choices, ultimately affecting public health too.

The Importance of Food Processing and Eating Behavior in Promoting Healthy and Sustainable Diets

Numerous association studies and findings from a controlled feeding trial have led to the suggestion that "processed" foods are bad for health. Processing technologies and food formulation are essential for food preservation and provide access to safe, nutritious, affordable, appealing and sustainable foods for millions globally. However, food processing at any level can also cause negative health consequences that result from thermal destruction of vitamins; formation of toxins such as acrylamide; or excessive intakes of salt, sugar, and fat. Research on ultraprocessed foods centers on food composition and formulation. In addition, many modern food formulations can have poor nutritional quality and higher energy density. We outline the role of processing in the provision of a safe and secure food supply and explore the characteristics of processed foods that promote greater energy intake. Despite the potential for negative health effects, food processing and formulation represent an opportunity to apply the latest developments in technology and ingredient innovation to improve the food supply by creating foods that decrease the risk of overeating. Expected final online publication date for the Annual Review of Nutrition, Volume 42 is August 2022. Please see http://www.annualreviews.org/page/journal/pubdates for revised estimates.

Higher-Order Inputs Involved in Appetite Control

The understanding of the neural control of appetite sheds light on the pathogenesis of eating disorders such as anorexia nervosa and obesity. Both diseases are a result of maladaptive eating behaviors (overeating or undereating) and are associated with life-threatening health problems. The fine regulation of appetite involves genetic, physiological, and environmental factors, which are detected and integrated in the brain by specific neuronal populations. For centuries, the hypothalamus has been the center of attention in the scientific community as a key regulator of appetite. The hypothalamus receives and sends axonal projections to several other brain regions that are important for the integration of sensory and emotional information. These connections ensure that appropriate behavioral decisions are made depending on the individual's emotional state and environment. Thus, the mechanisms by which higher-order brain regions integrate exteroceptive information to coordinate feeding is of great importance. In this review, we will focus on the functional and anatomical projections connecting the hypothalamus to the limbic system and higher-order brain centers in the cortex. We will also address the mechanisms by which specific neuronal populations located in higher-order centers regulate appetite and how maladaptive eating behaviors might arise from altered connections among cortical and subcortical areas with the hypothalamus.

A Neuroeconomics Approach to Obesity

Obesity is a heterogeneous condition that is affected by physiological, behavioral, and environmental factors. Value-based decision making is a useful framework for integrating these factors at the individual level. The disciplines of behavioral economics and reinforcement learning provide tools for identifying specific cognitive and motivational processes that may contribute to the development and maintenance of obesity. Neuroeconomics complements these disciplines by studying the neural mechanisms underlying these processes. We surveyed recent literature on individual decision characteristics that are most frequently implicated in obesity: discounting the value of future outcomes, attitudes toward uncertainty, and learning from rewards and punishments. Our survey highlighted both consistent and inconsistent behavioral findings. These findings underscore the need to examine multiple processes within individuals to identify unique behavioral profiles associated with obesity. Such individual characterization will inform future studies on the neurobiology of obesity as well as the design of effective interventions that are individually tailored.

Correlations Between Endocrine Hormones and Cognitive Function in Patients with Obesity: a Cross-sectional Study

BACKGROUND

Obesity not only affects physical and mental conditions, but also influences cognitive function. Endocrine hormones may influence the risk of obesity and severe obesity. Our study investigated the influences of changes in levels of endocrine hormones on cognitive function in patients with obesity and severe obesity.

METHODS

We used the MATRICS Consensus Cognitive Battery (MCCB) to evaluate cognitive function in the groups of healthy control (HC), obesity (OB), and severe obesity (SOB). We detected the levels of endocrine hormones and cortisol at 8:00 am in the three groups. We statistically analyzed differences in cognitive function and levels of endocrine hormones among the three groups, and performed linear correlation analysis of cortisol level and cognitive function. Using mediation analysis, we assessed the influences of body mass index (BMI) on endocrine levels and cognitive function.

RESULTS

Our findings revealed that OB and SOB groups exhibited a lower level of cortisol than HC group. Among the three groups, we found significant differences in verbal learning (F = 4.433, P = 0.014), social cognition (F = 4.778, P = 0.010), and total cognition (F = 2.989, P = 0.008). After post hoc Bonferroni correction, we noted that SOB group had worse scores in the above-mentioned three areas than OB and HC groups. Moreover, except for working memory and visual cognition, we identified that the degree of cognitive impairment in SOB group was more severe than that in OB group. In our study, mediation analysis showed a mediating effect of BMI on cortisol level and verbal learning. We also found correlations between cortisol level and attention/alertness (r = 0.277, P = 0.003), between cortisol level and verbal learning (r = 0.205, P = 0.030), and between BMI and verbal learning (r =  - 0.192, P = 0.043).

CONCLUSION

In our study, patients in both OB and SOB groups experienced a widespread cognitive impairment. We also found that patients with severe obesity had more severe cognitive impairment. Cognitive impairment could be mediated by abnormal cortisol metabolism, and BMI could be a mediating factor in regulation of cortisol level.

Sex Differences in Cognition Across Aging

Sex and gender differences are seen in cognitive disturbances in a variety of neurological and psychiatry diseases. Men are more likely to have cognitive symptoms in schizophrenia whereas women are more likely to have more severe cognitive symptoms with major depressive disorder and Alzheimer's disease. Thus, it is important to understand sex and gender differences in underlying cognitive abilities with and without disease. Sex differences are noted in performance across various cognitive domains - with males typically outperforming females in spatial tasks and females typically outperforming males in verbal tasks. Furthermore, there are striking sex differences in brain networks that are activated during cognitive tasks and in learning strategies. Although rarely studied, there are also sex differences in the trajectory of cognitive aging. It is important to pay attention to these sex differences as they inform researchers of potential differences in resilience to age-related cognitive decline and underlying mechanisms for both healthy and pathological cognitive aging, depending on sex. We review literature on the progressive neurodegenerative disorder, Alzheimer's disease, as an example of pathological cognitive aging in which human females show greater lifetime risk, neuropathology, and cognitive impairment, compared to human males. Not surprisingly, the relationships between sex and cognition, cognitive aging, and Alzheimer's disease are nuanced and multifaceted. As such, this chapter will end with a discussion of lifestyle factors, like education and diet, as modifiable factors that can alter cognitive aging by sex. Understanding how cognition changes across age and contributing factors, like sex differences, will be essential to improving care for older adults.

Effects of dietary restriction on cognitive function: a systematic review and meta-analysis

BACKGROUND

Potential positive link between cognitive function and dietary restriction has been widely concerned. The present study describes a systematic review and preliminary meta-analysis to assess the efficacy of dietary restriction on cognitive function. We classified dietary restrictions as Calories Restriction (CR) and Intermittent Fasting (IF).

METHOD

This systematic review and meta-analysis conducted following the guidelines of the Preferred Reporting Items for Systematic Reviews and Meta-Analysis Statement (PRISMA) Checklist, Databases including PubMed, Embase, Web of Science, and the Cochrane Library were searched for randomized controlled trials (RCTs) assessing the cognition effectiveness of dietary restriction from database inception to Sep 2021.

RESULT

Eleven RCTs met the inclusion criteria in the systematic review and meta-analysis. The overall effect of dietary restriction on cognitive function is SMD = 0.22 (95% CI: 0.09-0.34, p < 0.01). The effect on global function SMD = 0.35 (95% CI: 0.04-0.65, p < 0.05) and memory SMD = 0.18 (95% CI: 0.00-0.35, p = 0.05) is significant. MCI showed the best effectiveness SMD = 0.36 (95% CI: 0.05-0.68, p < 0.05), followed by the normal weight population SMD = 0.28 (95% CI: 0.03-0.52, p < 0.05) and overweight population SMD = 0.20 (95% CI: 0.06-0.34, p < 0.01). No statistically significant difference showed between IF and CR (p > 0.05).

CONCLUSION

Our study demonstrated that dietary restriction has varying degrees of positive effect on cognitive function in overweight/normal-weight people and MCI. However, it should be cautious when generalizing to other populations. Additional high-quality, large-scale, cohort and intervention studies are needed to further assess the effectiveness of dietary restriction on cognition.

Transcranial direct current stimulation to modulate brain reactivity to food cues in overweight and obese adults: study protocol for a randomized controlled trial with fMRI (NeuroStim-Obesity)

Background

With increasing obese populations worldwide, developing interventions to modulate food-related brain processes and functions is particularly important. Evidence suggests that transcranial direct current stimulation (tDCS) over the dorsolateral prefrontal cortex (DLPFC) may modulate the reward–control balance towards facilitation of cognitive control and possible suppression of reward-related mechanisms that drive food cue-induced craving. This protocol describes a clinical trial that investigates the neurocognitive mechanisms of action for tDCS to modulate food cue-reactivity and cravings in people with obesity.

Method

The NeuroStim-Obesity trial is a prospective, randomized, sham-controlled, double-blind single-session tDCS trial targeting food craving in those with obesity or overweighed. Once randomized, 64 adults with obesity or overweighed complete one session in which they receive either active or sham tDCS over the DLPFC (anode F4 and cathode F3, 2 mA intensity for 20 min). The primary outcome is change in neural response to the food cue-reactivity task in the ventral striatum after a single-session bilateral tDCS compared to sham stimulation. Secondary outcomes include changes in food craving evaluated by the Food Craving Questionnaire-State (FCQ-S). We will also explore the predictive role of brain structure and functional networks assessed by structural and functional magnetic resonance imaging (MRI) during both task performance and the resting-state that are acquired pre- and post-intervention to predict response to tDCS.

Discussion

The results will provide novel insight into neuroscience for the efficacy of tDCS and will advance the field towards precision medicine for obesity. Exploratory results will examine the potential predictive biomarkers for tDCS response and eventually provide personalized intervention for the treatment of obesity.

Trial registration

Iranian Registry of Clinical Trials (IRCT) IRCT20121020011172N4. Retrospectively registered on 4 June 2020

Aging versus youth: Endocrine aspects of vulnerability for COVID-19

Coronavirus Disease 2019 (COVID-19) is characterized with a wide range of clinical presentations from asymptomatic to severe disease. In patients with severe disease, the main causes of mortality have been acute respiratory distress syndrome, cytokine storm and thrombotic events. Although all factors that may be associated with disease severity are not yet clear, older age remains a leading risk factor. While age-related immune changes may be at the bottom of severe course of COVID-19, age-related hormonal changes have considerable importance due to their interactions with these immune alterations, and also with endothelial dysfunction and comorbid cardiometabolic disorders. This review aims to provide the current scientific evidence on the pathogenetic mechanisms underlying the pathway to severe COVID-19, from a collaborative perspective of age-related immune and hormonal changes together, in accordance with the clinical knowledge acquired thus far.

Obesogenic diets induce anxiety in rodents: A systematic review and meta-analysis

Obesity and mood disorders have been linked in a positive feedback loop. However, due to the bidirectional relationship between obesity and mental health, it is not clear whether anxiety is correlated with or caused by consumption of obesogenic diets. Here, we present a meta-analysis on the effects of dietary manipulation on rodent behavior in the elevated plus maze and open field test, the most common tests of anxiety-like behavior in animal models. The main dataset examined effects of obesogenic diets on time spent in the open and movement around the mazes. Auxiliary datasets examined effects of caloric restriction and protein restriction. Obesogenic diets had a negative effect on the time spent in the open overall. Effects were stronger in males than females. No effect of diet on locomotion was found, indicating that increases in anxiety-like behavior are not due to altered activity levels. No consistent effect of caloric restriction was observed, whereas protein restriction was associated with an increase in the time spent in the open. We show that obesogenic diets have a causative effect on anxiety-like behaviors in rodents, and not via a change in activity. Further studies are required to determine why obesogenic diets induce these behavioral changes.

Long-term high-fat diet consumption by mice throughout adulthood induces neurobehavioral alterations and hippocampal neuronal remodeling accompanied by augmented microglial lipid accumulation

High-fat diet (HFD) consumption is generally associated with an increased risk of cognitive and emotional dysfunctions that constitute a sizeable worldwide health burden with profound social and economic consequences. Middle age is a critical time period that affects one's health later in life; pertinently, the prevalence of HFD consumption is increasing among mature adults. Given the growing health-related economic burden imposed globally by increasing rates of noncommunicable diseases in rapidly aging populations, along with the pervasive but insidious health impairments associated with HFD consumption, it is critically important to understand the effects of long-term HFD consumption on brain function and to gain insights into their potential underlying mechanisms. In the present study, adult male C57BL/6J mice were randomly assigned a control diet (CD, 10 kJ% from fat) or an HFD (60 kJ% from fat) for 6 months (6 M) or 9 months (9 M) followed by behavioral tests, serum biochemical analysis, and histological examinations of both the dorsal and ventral regions of the hippocampus. In both the 6 M and 9 M cohorts, mice that consumed an HFD exhibited poorer memory performance in the Morris water maze test (MWM) and greater depression- and anxiety-like behavior during the open field test (OFT), sucrose preference test (SPT) and forced swim test (FST) than control mice. Compared with age-matched mice in the CD group, mice in the HFD group showed abnormal hippocampal neuronal morphology, which was particularly evident in the ventral hippocampus. Hippocampal microglia in mice in the HFD group generally had a more activated phenotype evidenced by a smaller microglial territory area and increased cluster of differentiation 68 (CD68, a marker of phagocytic activity) immunoreactivity, while the microglial density in the dentate gyrus (DG) was decreased, indicating microglial decline. The engulfment of postsynaptic density 95 (PSD95, a general postsynaptic marker) puncta by microglia was increased in the HFD groups. Histological analysis of neutral lipids using a fluorescent probe (BODIPY) revealed that the total neutral lipid content in regions of interests (ROIs) and the lipid load in microglia were increased in the HFD group relative to the age-matched CD group. In summary, our results demonstrated that chronic HFD consumption from young adulthood to middle age induced anxiety- and depression-like behavior as well as memory impairment. The negative influence of chronic HFD consumption on behavioral and hippocampal neuroplasticity appears to be linked to a change in microglial phenotype that is accompanied by a remarkable increase in cellular lipid accumulation. These observations highlighting the potential to target lipid metabolism deficits to reduce the risk of HFD-associated emotional dysfunctions.

Chronic exposure to cafeteria-style diet in rats alters sweet taste preference and reduces motivation for, but not 'liking' of sucrose

Obesity is associated with changes to taste perception and brain reward circuitry. It is important to understand how these effects alter the preference for palatable foods and drinks, given that these are widely consumed, and leading risk factors for obesity. This study examined the effects of diet-induced obesity on sweet taste preference by analysing the microstructure of licking for sugar solutions and assessing pERK expression in the nucleus accumbens shell and insula. Adult male Sprague-Dawley rats were fed standard chow (Control; n = 16) or a varied, palatable cafeteria diet (Caf; n = 16) for 12 weeks. Two-choice preference tests between 2%, 8% and 32% sucrose solutions were conducted at baseline and in weeks 11-12 of the diet. Rats in the Caf group trebled energy intake and doubled weight gain relative to controls. In tests held under water restriction after 11 weeks of diet, the Control group reliably preferred higher sucrose concentrations (i.e., 32% > 8% > 2%). Relative to controls, the Caf group showed a stronger preference for 32% vs. 2% sucrose, lower preference for 32% vs. 8% sucrose, and were indifferent to 8% vs. 2% sucrose. Testing without water restriction increased preference for higher sucrose concentrations in both groups. Chronic Caf diet increased the latency to lick, decreased total licks and reduced alternations between spouts, but did not alter lick cluster size, a measure of hedonic appraisal, on any test. Following a final exposure to a novel sucrose concentration, neuronal activity (pERK) in the insula and nucleus accumbens shell was significantly reduced in the Caf group. Results indicate that differences in 'liking' do not underlie obesity-induced changes to sweet taste preference.

Pediococcus acidilactici FZU106 alleviates high-fat diet-induced lipid metabolism disorder in association with the modulation of intestinal microbiota in hyperlipidemic rats

Probiotics have been proved to have beneficial effects in improving hyperlipidemia. The purpose of the current research was to investigate the ameliorative effects of Pediococcus acidilactici FZU106, isolated from the traditional brewing of Hongqu rice wine, on lipid metabolism and intestinal microbiota in high-fat diet (HFD)-induced hyperlipidemic rats. Results showed that P. acidilactici FZU106 intervention obviously inhibited the abnormal increase of body weight, ameliorated serum and liver biochemical parameters related to lipid metabolism and oxidative stress. Histopathological evaluation also showed that P. acidilactici FZU106 could significantly reduce the excessive lipid accumulation in liver caused by HFD-feeding. Furthermore, P. acidilactici FZU106 intervention significantly increased the short-chain fatty acids (SCFAs) levels in HFD-fed rats, which was closely related to the changes of intestinal microbial composition and metabolism. Intestinal microbiota profiling by high-throughput sequencing demonstrated that P. acidilactici FZU106 intervention evidently increased the proportion of Butyricicoccus, Pediococcus, Rothia, Globicatella and [Eubacterium]_coprostanoligenes_group, and decreased the proportion of Corynebacterium_1, Psychrobacter, Oscillospira, Facklamia, Pseudogracilibacillus, Clostridium_innocuum_group, Enteractinococcus and Erysipelothrix in HFD-fed rats. Additionally, P. acidilactici FZU106 significantly regulated the mRNA levels of liver genes (including CD36, CYP7A1, SREBP-1c, BSEP, LDLr and HMGCR) involved in lipid metabolism and bile acid homeostasis. Therefore, these findings support the possibility that P. acidilactici FZU106 has the potential to reduce the disturbance of lipid metabolism by regulating intestinal microflora and liver gene expression profiles.

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Pediococcus acidilactici FZU106 protects against hyperlipidemia.

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Pediococcus acidilactici FZU106 regulates serum and liver lipid levels.

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Pediococcus acidilactici FZU106 regulates intestinal microbial composition.

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Pediococcus acidilactici FZU106 regulates lipid metabolism related genes.