Dietary sugars and non-caloric sweeteners elicit different homeostatic and hedonic responses in the brain

Neural responses to oral administration of erythritol vs. sucrose and sucralose explain differences in subjective liking ratings

INTRODUCTION

High sugar intake is associated with many chronic diseases. However, non-caloric sweeteners (NCSs) might fail to successfully replace sucrose due to the mismatch between their rewarding sweet taste and lack of caloric content. The natural NCS erythritol has been proposed as a sugar substitute due to its satiating properties despite being non-caloric. We aimed to compare brain responses to erythritol vs. sucrose and the artificial NCS sucralose in a priori taste, homeostatic, and reward brain regions of interest (ROIs).

METHODS

We performed a within-subject, single-blind, counterbalanced fMRI study in 30 healthy men (mean ± SEM age:24.3 ± 0.8 years, BMI:22.3 ± 0.3 kg/m2). Before scanning, we individually matched the concentrations of both NCSs to the perceived sweetness intensity of a 10% sucrose solution. During scanning, participants received 1 mL sips of the individually titrated equisweet solutions of sucrose, erythritol, and sucralose, as well as water. After each sip, they rated subjective sweetness liking.

RESULTS

Liking ratings were significantly higher for sucrose and sucralose vs. erythritol (both pHolm = 0.0037); water ratings were neutral. General Linear Model (GLM) analyses of brain blood oxygen level-depended (BOLD) responses at qFDR<0.05 showed no differences between any of the sweeteners in a priori ROIs, but distinct differences were found between the individual sweeteners and water. These results were confirmed by Bayesian GLM and machine learning-based models. However, several brain response patterns mediating the differences in liking ratings between the sweeteners were found in whole-brain multivariate mediation analyses. Both subjective and neural responses showed large inter-subject variability.

CONCLUSION

We found lower liking ratings in response to oral administration of erythritol vs. sucrose and sucralose, but no differences in neural responses between any of the sweeteners in a priori ROIs. However, differences in liking ratings between erythritol vs. sucrose or sucralose are mediated by multiple whole-brain response patterns.

Binge-Eating Precursors in Children and Adolescents: Neurodevelopment, and the Potential Contribution of Ultra-Processed Foods

Binge-eating disorder (BED) is a highly prevalent disorder. Subthreshold BED conditions (sBED) are even more frequent in youth, but their significance regarding BED etiology and long-term prognosis is unclear. A better understanding of brain findings associated with BED and sBED, in the context of critical periods for neurodevelopment, is relevant to answer such questions. The present narrative review starts from the knowledge of the development of emotional self-regulation in youth, and the brain circuits supporting emotion-regulation and eating behaviour. Next, neuroimaging studies with sBED and BED samples will be reviewed, and their brain-circuitry overlap will be examined. Deficits in inhibition control systems are observed to precede, and hyperactivity of reward regions to characterize, sBED, with overlapping findings in BED. The imbalance between reward/inhibition systems, and the implication of interoception/homeostatic processing brain systems should be further examined. Recent knowledge of the potential impact that the high consumption of ultra-processed foods in paediatric samples may have on these sBED/BED-associated brain systems is then discussed. There is a need to identify, early on, those sBED individuals at risk of developing BED at neurodevelopmental stages when there is a great possibility of prevention. However, more neuroimaging studies with sBED/BED pediatric samples are needed.

Nutrient infusion evoked magnetic resonance imaging signal in the human hypothalamus

BACKGROUND

The hypothalamus receives ingested nutrient information via ascending gut-related projections and plays a significant role in the regulation of food intake. Human neuroimaging studies have observed changes in the activity or connectivity of the hypothalamus in response to nutrient ingestion. However, previous neuroimaging studies have not yet assessed differences in temporal changes of hypothalamic responses to various nutrients in humans. Thus a repeated measures functional magnetic resonance imaging (fMRI) study using 30-min scans was designed to examine differences in hypothalamic responses to various nutrients.

METHODS

In this study, 18 healthy adults (mean age, 22.4 years; standard deviation, 4.8; age range, 19-39 years; 11 males and seven females) underwent fMRI sessions. On the day of each session, one of the four solutions (200 ml of monosodium glutamate, glucose, safflower oil emulsion, or saline) was administered to participants while fMRI scanning.

RESULTS

Infused amino acid and glucose, but not lipid emulsion, increased lateral hypothalamic responses as compared to a saline infusion ([x, y, z] = [4, -4, -10], z = 2.96). In addition, only hypothalamic responses to saline, but not those to the infusion of other nutrients, elicited a subjective sensation of hunger.

CONCLUSION

These findings suggest that lateral hypothalamic responses to ingested nutrients may mediate homeostatic sensations in humans.

Early-life low-calorie sweetener consumption disrupts glucose regulation, sugar-motivated behavior, and memory function in rats

Low-calorie sweetener (LCS) consumption in children has increased dramatically due to its widespread presence in the food environment and efforts to mitigate obesity through sugar replacement. However, mechanistic studies on the long-term impact of early-life LCS consumption on cognitive function and physiological processes are lacking. Here, we developed a rodent model to evaluate the effects of daily LCS consumption (acesulfame potassium, saccharin, or stevia) during adolescence on adult metabolic, behavioral, gut microbiome, and brain transcriptomic outcomes. Results reveal that habitual early-life LCS consumption impacts normal postoral glucose handling and impairs hippocampal-dependent memory in the absence of weight gain. Furthermore, adolescent LCS consumption yielded long-term reductions in lingual sweet taste receptor expression and brought about alterations in sugar-motivated appetitive and consummatory responses. While early-life LCS consumption did not produce robust changes in the gut microbiome, brain region-specific RNA-Seq analyses reveal LCS-induced changes in collagen- and synaptic signaling-related gene pathways in the hippocampus and nucleus accumbens, respectively, in a sex-dependent manner. Collectively, these results reveal that habitual early-life LCS consumption has long-lasting implications for glucoregulation, sugar-motivated behavior, and hippocampal-dependent memory in rats, which may be based in part on changes in nutrient transporter, sweet taste receptor, and central gene pathway expression.

Mapping the Homeostatic and Hedonic Brain Responses to Stevia Compared to Caloric Sweeteners and Water: A Double-Blind Randomised Controlled Crossover Trial in Healthy Adults

Non-nutritive sweeteners have potential effects on brain function. We investigated neural correlates of responses to beverages differing in sweetness and calories. Healthy participants completed 4 randomised sessions: water vs. water with stevia, glucose, or maltodextrin. Blood-oxygenation level-dependent (BOLD) contrast was monitored for 30 min post-ingestion by functional Magnetic Resonance Imaging. A food visual probe task at baseline was repeated at 30 min. A significant interaction of taste-by-calories-by-time was demonstrated mainly in motor, frontal, and insula cortices. Consumption of the stevia-sweetened beverage resulted in greater BOLD decrease, especially in the 20-30 min period, compared to other beverages. There was a significant interaction of taste-by-time in BOLD response in gustatory and reward areas; sweet beverages induced greater reduction in BOLD compared to non-sweet. The interaction calories-by-time showed significantly greater incremental area under the curve in thalamic, visual, frontal, and parietal areas for glucose and maltodextrin 10-20 min post-consumption only, compared to water. In the visual cue task, the water demonstrated an increased response in the visual cortex to food images post-consumption; however, no difference was observed for the three sweet/caloric beverages. In conclusion, both sweet taste and calories exert modulatory effects, but stevia showed a more robust and prolonged effect.

Dissecting ultra-processed foods and drinks: Do they have a potential to impact the brain?

Ultra-processed foods and drinks (UPF) are formulation of ingredients, mostly of exclusive industrial use, that result from a series of industrial processes. They usually have a low nutrient but high energy density, with a high content of saturated and trans fats, and added sugars. In addition, they have characteristic organoleptic properties, and usually contain sophisticated additives, including artificial sweeteners, to intensify their sensory qualities and imitate the appearance of minimally processed foods. In addition, recent research has warned about the presence of chemicals (e.g., bisphenol) and neo-formed contaminants in these products. UPF production and consumption growth have been spectacular in the last decades, being specially consumed in children and adolescents. UPF features have been associated with a range of adverse health effects such as overeating, the promotion of inflammatory and oxidative stress processes, gut dysbiosis, and metabolic dysfunction including problems in glucose regulation. The evidence that these UPF-related adverse health effects may have on the neural network implicated in eating behavior are discussed, including the potential impact on serotonergic and dopaminergic neurotransmission, brain integrity and function. We end this review by placing UPF in the context of current food environments, by suggesting that an increased exposure to these products through different channels, such as marketing, may contribute to the automatic recruitment of the brain regions associated with food consumption and choice, with a detrimental effect on inhibitory-related prefrontal cortices. While further research is essential, preliminary evidence point to UPF consumption as a potential detrimental factor for brain health and eating behavior.

A High-Sugar Diet Consumption, Metabolism and Health Impacts with a Focus on the Development of Substance Use Disorder: A Narrative Review

Carbohydrates are important macronutrients in human and rodent diet patterns that play a key role in crucial metabolic pathways and provide the necessary energy for proper body functioning. Sugar homeostasis and intake require complex hormonal and nervous control to proper body energy balance. Added sugar in processed food results in metabolic, cardiovascular, and nervous disorders. Epidemiological reports have shown enhanced consumption of sweet products in children and adults, especially in reproductive age and in pregnant women, which can lead to the susceptibility of offspring’s health to diseases in early life or in adulthood and proneness to mental disorders. In this review, we discuss the impacts of high-sugar diet (HSD) or sugar intake during the perinatal and/or postnatal periods on neural and behavioural disturbances as well as on the development of substance use disorder (SUD). Since several emotional behavioural disturbances are recognized as predictors of SUD, we also present how HSD enhances impulsive behaviour, stress, anxiety and depression. Apart from the influence of HSD on these mood disturbances, added sugar can render food addiction. Both food and addictive substances change the sensitivity of the brain rewarding neurotransmission signalling. The results of the collected studies could be important in assessing sugar intake, especially via maternal dietary patterns, from the clinical perspective of SUD prevention or pre-existing emotional disorders. Methodology: This narrative review focuses on the roles of a high-sugar diet (HSD) and added sugar in foods and on the impacts of glucose and fructose on the development of substance use disorder (SUD) and on the behavioural predictors of drugs abuse. The literature was reviewed by two authors independently according to the topic of the review. We searched the PubMed and Scopus databases and Multidisciplinary Digital Publishing Institute open access scientific journals using the following keyword search strategy depending on the theme of the chapter: “high-sugar diet” OR “high-carbohydrate diet” OR “sugar” OR “glucose” OR “fructose” OR “added sugar” AND keywords. We excluded inaccessible or pay-walled articles, abstracts, conference papers, editorials, letters, commentary, and short notes. Reviews, experimental studies, and epidemiological data, published since 1990s, were searched and collected depending on the chapter structure. After the search, all duplicates are thrown out and full texts were read, and findings were rescreened. After the selection process, appropriate papers were included to present in this review.

The Effect of Artificial Sweeteners Use on Sweet Taste Perception and Weight Loss Efficacy: A Review

Excessive consumption of sugar-rich foods is currently one of the most important factors that has led to the development of the global pandemic of obesity. On the other hand, there is evidence that obesity contributes to reduced sensitivity to sweet taste and hormonal changes affecting appetite, leading to an increased craving for sweets. A high intake of sugars increases the caloric value of the diet and, consequently, leads to weight gain. Moreover, attention is drawn to the concept of the addictive properties of sugar and sugary foods. A potential method to reduce the energy value of diet while maintaining the sweet taste is using non-nutritive sweeteners (NNS). NNS are commonly used as table sugar substitutes. This wide group of chemical compounds features high sweetness almost without calories due to its high sweetening strength. NNS include aspartame, acesulfame-K, sucralose, saccharin, cyclamate, neohesperidin dihydrochalcone (neohesperidin DC), neotame, taumatin, and advantame. The available evidence suggests that replacing sugar with NNS may support weight control. However, the effect of NNS on the regulation of appetite and sweet taste perception is not clear. Therefore, the review aimed to summarize the current knowledge about the use of NNS as a potential strategy for weight loss and their impact on sweet taste perception. Most studies have demonstrated that consumption of NNS-sweetened foods does not increase sweetness preference orenergy intake. Nonetheless, further research is required to determine the long-term effects of NNS on weight management.

Obesity and Sex-Related Associations With Differential Effects of Sucralose vs Sucrose on Appetite and Reward Processing: A Randomized Crossover Trial

IMPORTANCE

Nonnutritive sweeteners (NNSs) are used as an alternative to nutritive sweeteners to quench desire for sweets while reducing caloric intake. However, studies have shown mixed results concerning the effects of NNSs on appetite, and the associations between sex and obesity with reward and appetitive responses to NNS compared with nutritive sugar are unknown.

OBJECTIVE

To examine neural reactivity to different types of high-calorie food cues (ie, sweet and savory), metabolic responses, and eating behavior following consumption of sucralose (NNS) vs sucrose (nutritive sugar) among healthy young adults.

DESIGN, SETTING, AND PARTICIPANTS

In a randomized, within-participant, crossover trial including 3 separate visits, participants underwent a functional magnetic resonance imaging task measuring blood oxygen level-dependent signal in response to visual cues. For each study visit, participants arrived at the Dornsife Cognitive Neuroimaging Center of University of Southern California at approximately 8:00 am after a 12-hour overnight fast. Blood was sampled at baseline and 10, 35, and 120 minutes after participants received a drink containing sucrose, sucralose, or water to measure plasma glucose, insulin, glucagon-like peptide(7-36), acyl-ghrelin, total peptide YY, and leptin. Participants were then presented with an ad libitum meal. Participants were right-handed, nonsmokers, weight-stable for at least 3 months before the study visits, nondieters, not taking medication, and with no history of eating disorders, illicit drug use, or medical diagnoses. Data analysis was performed from March 2020 to March 2021.

INTERVENTIONS

Participants ingested 300-mL drinks containing either sucrose (75 g), sucralose (individually sweetness matched), or water (as a control).

MAIN OUTCOMES AND MEASURES

Primary outcomes of interest were the effects of body mass index (BMI) status and sex on blood oxygen level-dependent signal to high-calorie food cues, endocrine, and feeding responses following sucralose vs sucrose consumption. Secondary outcomes included neural, endocrine, and feeding responses following sucrose vs water and sucralose vs water (control) consumption, and cue-induced appetite ratings following sucralose vs sucrose (and vs water).

RESULTS

A total of 76 participants were randomized, but 2 dropped out, leaving 74 adults (43 women [58%]; mean [SD] age, 23.40 [3.96] years; BMI range, 19.18-40.27) who completed the study. In this crossover design, 73 participants each received water (drink 1) and sucrose (drink 2), and 72 participants received water (drink 1), sucrose (drink 2), and sucralose (drink 3). Sucrose vs sucralose was associated with greater production of circulating glucose, insulin, and glucagon-like peptide-1 and suppression of acyl-ghrelin, but no differences were found for peptide YY or leptin. BMI status by drink interactions were observed in the medial frontal cortex (MFC; P for interaction < .001) and orbitofrontal cortex (OFC; P for interaction = .002). Individuals with obesity (MFC, β, 0.60; 95% CI, 0.38 to 0.83; P < .001; OFC, β, 0.27; 95% CI, 0.11 to 0.43; P = .002), but not those with overweight (MFC, β, 0.02; 95% CI, -0.19 to 0.23; P = .87; OFC, β, -0.06; 95% CI, -0.21 to 0.09; P = .41) or healthy weight (MFC, β, -0.13; 95% CI, -0.34 to 0.07; P = .21; OFC, β, -0.08; 95% CI, -0.23 to 0.06; P = .16), exhibited greater responsivity in the MFC and OFC to savory food cues after sucralose vs sucrose. Sex by drink interactions were observed in the MFC (P for interaction = .03) and OFC (P for interaction = .03) after consumption of sucralose vs sucrose. Female participants had greater MFC and OFC responses to food cues (MFC high-calorie vs low-calorie cues, β, 0.21; 95% CI, 0.05 to 0.37; P = .01; MFC sweet vs nonfood cues, β, 0.22; 95% CI, 0.02 to 0.42; P = .03; OFC food vs nonfood cues, β, 0.12; 95% CI, 0.02 to 0.22; P = .03; and OFC sweet vs nonfood cues, β, 0.15; 95% CI, 0.03 to 0.27; P = .01), but male participants' responses did not differ (MFC high-calorie vs low-calorie cues, β, 0.01; 95% CI, -0.19 to 0.21; P = .90; MFC sweet vs nonfood cues, β, -0.04; 95% CI, -0.26 to 0.18; P = .69; OFC food vs nonfood cues, β, -0.08; 95% CI, -0.24 to 0.08; P = .32; OFC sweet vs nonfood cues, β, -0.11; 95% CI, -0.31 to 0.09; P = .31). A sex by drink interaction on total calories consumed during the buffet meal was observed (P for interaction = .03). Female participants consumed greater total calories (β, 1.73; 95% CI, 0.38 to 3.08; P = .01), whereas caloric intake did not differ in male participants (β, 0.68; 95% CI, -0.99 to 2.35; P = .42) after sucralose vs sucrose ingestion.

CONCLUSIONS AND RELEVANCE

These findings suggest that female individuals and those with obesity may be particularly sensitive to disparate neural responsivity elicited by sucralose compared with sucrose consumption.

TRIAL REGISTRATION

ClinicalTrials.gov Identifier: NCT02945475.

Microbiota's Role in Diet-Driven Alterations in Food Intake: Satiety, Energy Balance, and Reward

The gut microbiota plays a key role in modulating host physiology and behavior, particularly feeding behavior and energy homeostasis. There is accumulating evidence demonstrating a role for gut microbiota in the etiology of obesity. In human and rodent studies, obesity and high-energy feeding are most consistently found to be associated with decreased bacterial diversity, changes in main phyla relative abundances and increased presence of pro-inflammatory products. Diet-associated alterations in microbiome composition are linked with weight gain, adiposity, and changes in ingestive behavior. There are multiple pathways through which the microbiome influences food intake. This review discusses these pathways, including peripheral mechanisms such as the regulation of gut satiety peptide release and alterations in leptin and cholecystokinin signaling along the vagus nerve, as well as central mechanisms, such as the modulation of hypothalamic neuroinflammation and alterations in reward signaling. Most research currently focuses on determining the role of the microbiome in the development of obesity and using microbiome manipulation to prevent diet-induced increase in food intake. More studies are necessary to determine whether microbiome manipulation after prolonged energy-dense diet exposure and obesity can reduce intake and promote meaningful weight loss.

Analysis of Caloric and Noncaloric Sweeteners Present in Dairy Products Aimed at the School Market and Their Possible Effects on Health

Over the past decades, Mexico has become one of the main sweetener-consuming countries in the world. Large amounts of these sweeteners are in dairy products aimed at the children’s market in various presentations such as yogurt, flavored milk, flan, and cheeses. Although numerous studies have shown the impact of sweeteners in adults, the current evidence for children is insufficient and discordant to determine if these substances have any risk or benefit on their well-being. Therefore, this study aimed to describe the sweeteners present in 15 dairy products belonging to the school-age children’s market in Mexico and their impact on health. These dairy products were selected through a couple of surveys directed at parents of school-age children. After that, the list of ingredients of each product was analyzed to identify their sweetener content. From there, exhaustive bibliographic research on sweeteners and their possible health effects was carried out, which included 109 articles and 18 studies. The results showed that at a neurological, endocrinological, cardiovascular, metabolic, osseous, renal, hepatic, dental, reticular, carcinogenic, and gut microbiota level; sucrose, fructose, high-fructose corn syrup, maltodextrins, sucralose, and acesulfame K, have a negative effect. While maltodextrins, stevia, polydextrose, and modified starch have a positive one. For these reasons, it is necessary to evaluate the advantages and disadvantages that the consumption of each sweetener entails, as well as a determination of the appropriate acceptable daily intake (ADI).

Disruption of lateral hypothalamic calorie detection by a free choice high fat diet

During the last few decades, the consumption of low-calorie sweeteners, as a substitute for caloric sweeteners, has sharply increased. Although research shows that caloric versus low-calorie sweeteners can have differential effects on the brain, it is unknown which neuronal populations are responsible for detecting the difference between the two types of sweeteners. Using in vivo two-photon calcium imaging, we investigated how drinking sucrose or sucralose (a low-calorie sweetener) affects the activity of glutamatergic neurons in the lateral hypothalamus. Furthermore, we explored the consequences of consuming a free-choice high fat diet on the calorie detection abilities of these glutamatergic neurons. We found that glutamatergic neurons indeed can discriminate sucrose from water and sucralose, and that consumption of a free-choice high fat diet shifts the glutamatergic neuronal response from sucrose-specific to sucralose-specific, thereby disrupting calorie detection. These results highlight the disruptive effects of a diet high in saturated fat on calorie detection in the lateral hypothalamus.

Neural mechanisms underlying the role of fructose in overfeeding

Fructose consumption has been linked with metabolic syndrome and obesity. Fructose-based sweeteners like high fructose corn syrup taste sweeter, improve food palatability, and are increasingly prevalent in our diet. The increase in fructose consumption precedes the rise in obesity and is a contributing driver to the obesity epidemic worldwide. The role of dietary fructose in obesity can be multifactorial by promoting visceral adiposity, hypertension, and insulin resistance. Interestingly, one emergent finding from human and animal studies is that dietary fructose promotes overfeeding. As the brain is a critical regulator of food intake, we reviewed the evidence that fructose can act in the brain and elucidated the major brain systems underlying fructose-induced overfeeding. We found that fructose acts on multiple interdependent brain systems to increase orexigenic drive and the incentive salience of food while decreasing the latency between food bouts and reducing cognitive control to disinhibit feeding. We concluded that the collective actions of fructose may promote feeding behavior by producing a hunger-like state in the brain.

Application of Magnetic Resonance Imaging in the Evaluation of Nutritional Status: A Literature Review with Focus on Dialysis Patients

Magnetic resonance imaging (MRI) is indispensable in clinical medicine for the morphological and tomographic evaluation of many parenchymal organs. With varied imaging methods, diverse biological information, such as the perfusion volume and measurements of metabolic products, can be obtained. In addition to conventional MRI for morphological assessment, diffusion-weighted MRI/diffusion tensor imaging is used to evaluate white matter structures in the brain; arterial spin labeling is used for cerebral blood flow evaluation; magnetic resonance elastography for fatty liver and cirrhosis evaluation; magnetic resonance spectroscopy for evaluation of metabolites in specific regions of the brain; and blood oxygenation level-dependent imaging for neurological exploration of eating behavior, obesity, and food perception. This range of applications will continue to expand in the future. Nutritional science is a multidisciplinary and all-inclusive field of research; therefore, there are many different applications of MRI. We present a literature review of MRI techniques that can be used to evaluate the nutritional status, particularly in patients on dialysis. We used MEDLINE as the information source, conducted a keyword search in PubMed, and found that, as a nutritional evaluation method, MRI has been used frequently to comprehensively and quantitatively evaluate muscle mass for the determination of body composition.

Effect of glucose and sucrose on cognition in healthy humans: a systematic review and meta-analysis of interventional studies

CONTEXT

Evidence suggests that plasma glucose levels may influence cognitive performance, but this has not been systematically reviewed and quantified.

OBJECTIVE

The aim of this review was to investigate the potential effects of glucose and sucrose, compared with placebo, on cognition in healthy humans.

DATA SOURCES

The electronic databases PubMed and Web of Science were searched up to December 2019. Reference lists of selected articles were checked manually.

STUDY SELECTION

Randomized controlled trials or crossover trials that compared glucose or sucrose with placebo for effects on cognition were eligible.

DATA EXTRACTION

Potentially eligible articles were selected independently by 2 authors. Risk of bias was assessed through the Cochrane Collaboration tool. Standardized mean differences (SMDs) were obtained from random-effects meta-analyses for a subsample of studies that reported the same outcomes.

RESULTS

Thirty-seven trials were identified, of which 35 investigated the effect of glucose consumption compared with placebo on cognition. Two studies found no effect of glucose on cognition, while the others found mixed results. Only 3 of the 37 studies investigated the effects of sucrose intake, reporting mixed results. Meta-analyses revealed a significantly positive effect of glucose compared with control, but only when a verbal performance test (immediate word recall) was used in parallel-design studies (SMD = 0.61; 95%CI, 0.20-1.02; I2 = 0%). Twenty-four studies were classified as having high risk of bias for the selection procedure.

CONCLUSIONS

A limited body of evidence shows a beneficial effect of glucose in individuals performing immediate verbal tasks. High-quality trials with standardized cognitive measurements are needed to better establish the effect of glucose or sucrose on cognition.

SYSTEMATIC REVIEW REGISTRATION

PROSPERO registration number CRD42019122939.

The Gut-Brain Axis and Its Role in Controlling Eating Behavior in Intestinal Inflammation

Malnutrition represents a major problem in the clinical management of the inflammatory bowel disease (IBD). Presently, our understanding of the cross-link between eating behavior and intestinal inflammation is still in its infancy. Crohn's disease patients with active disease exhibit strong hedonic desires for food and emotional eating patterns possibly to ameliorate feelings of low mood, anxiety, and depression. Impulsivity traits seen in IBD patients may predispose them to palatable food intake as an immediate reward rather than concerns for future health. The upregulation of enteroendocrine cells (EEC) peptide response to food intake has been described in ileal inflammation, which may lead to alterations in gut-brain signaling with implications for appetite and eating behavior. In summary, a complex interplay of gut peptides, psychological, cognitive factors, disease-related symptoms, and inflammatory burden may ultimately govern eating behavior in intestinal inflammation.

The Impact of Artificial Sweeteners on Body Weight Control and Glucose Homeostasis

A poor diet is one of the leading causes for non-communicable diseases. Due to the increasing prevalence of overweight and obesity, there is a strong focus on dietary overconsumption and energy restriction. Many strategies focus on improving energy balance to achieve successful weight loss. One of the strategies to lower energy intake is refraining from sugars and replacing them with artificial sweeteners, which maintain the palatability without ingesting calories. Nevertheless, the safety and health benefits of artificial sweeteners consumption remain a topic of debate within the scientific community and society at large. Notably, artificial sweeteners are metabolized differently from each other due to their different properties. Therefore, the difference in metabolic fate of artificial sweeteners may underlie conflicting findings that have been reported related to their effects on body weight control, glucose homeostasis, and underlying biological mechanisms. Thus, extrapolation of the metabolic effects of a single artificial sweetener to all artificial sweeteners is not appropriate. Although many rodent studies have assessed the metabolic effects of artificial sweeteners, long-term studies in humans are scarce. The majority of clinical studies performed thus far report no significant effects or beneficial effects of artificial sweeteners on body weight and glycemic control, but it should be emphasized that the study duration of most studies was limited. Clearly, further well-controlled, long-term human studies investigating the effects of different artificial sweeteners and their impact on gut microbiota, body weight regulation and glucose homeostasis, as well as the underlying mechanisms, are warranted.

Glucose and fat sensing in the human hypothalamus

Energy balance is centrally regulated by the brain through several interacting neuronal systems involving external, peripheral, and central factors within the brain. The hypothalamus integrates these factors and is the key brain area in the regulation of energy balance. In this review, we will explain the structure of the hypothalamus and its role in the regulation of energy balance. An important part of energy balance regulation is the sensing of nutrient status and availability. This review will focus on the sensing of the two main sources of energy by the hypothalamus: glucose and fat. As many common health problems and chronic diseases can be traced back to a disrupted hypothalamic function, we will also discuss hypothalamic sensing of glucose and fats in these pathologies. Finally, we will summarize the current knowledge and discuss how this may be applied clinically and for future research perspectives.

A rational review on the effects of sweeteners and sweetness enhancers on appetite, food reward and metabolic/adiposity outcomes in adults

Numerous strategies have been investigated to overcome the excessive weight gain that accompanies a chronic positive energy balance. Most approaches focus on a reduction of energy intake and the improvement of lifestyle habits. The use of high intensity artificial sweeteners, also known as non-caloric sweeteners (NCS), as sugar substitutes in foods and beverages, is rapidly developing. NCS are commonly defined as molecules with a sweetness profile of 30 times higher or more that of sucrose, scarcely contributing to the individual's net energy intake as they are hardly metabolized. The purpose of this review is first, to assess the impact of NCS on eating behaviour, including subjective appetite, food intake, food reward and sensory stimulation; and secondly, to assess the metabolic impact of NCS on body weight regulation, glucose homeostasis and gut health. The evidence reviewed suggests that while some sweeteners have the potential to increase subjective appetite, these effects do not translate in changes in food intake. This is supported by a large body of empirical evidence advocating that the use of NCS facilitates weight management when used alongside other weight management strategies. On the other hand, although NCS are very unlikely to impair insulin metabolism and glycaemic control, some studies suggest that NCS could have putatively undesirable effects, through various indirect mechanisms, on body weight, glycemia, adipogenesis and the gut microbiota; however there is insufficient evidence to determine the degree of such effects. Overall, the available data suggests that NCS can be used to facilitate a reduction in dietary energy content without significant negative effects on food intake behaviour or body metabolism, which would support their potential role in the prevention of obesity as a complementary strategy to other weight management approaches. More research is needed to determine the impact of NCS on metabolic health, in particular gut microbiota.

Impacts of Acute Sucralose and Glucose on Brain Activity during Food Decisions in Humans

It is not known how acute sucralose and glucose alter signaling within the brain when individuals make decisions about available food. Here we examine this using Food Bid Task in which participants bid on visually depicted food items, while simultaneously undergoing functional Magnetic Resonance Imaging. Twenty-eight participants completed three sessions after overnight fast, distinguished only by the consumption at the start of the session of 300 mL cherry flavored water with either 75 g glucose, 0.24 g sucralose, or no other ingredient. There was a marginally significant (p = 0.05) effect of condition on bids, with 13.0% lower bids after glucose and 16.6% lower bids after sucralose (both relative to water). Across conditions, greater activity within regions a priori linked to food cue reactivity predicted higher bids, as did greater activity within the medial orbitofrontal cortex and bilateral frontal pole. There was a significant attenuation within the a priori region of interest (ROI) after sucralose compared to water (p < 0.05). Activity after glucose did not differ significantly from either of the other conditions in the ROI, but an attenuation in signal was observed in the parietal cortex, relative to the water condition. Taken together, these data suggest attenuation of central nervous system (CNS) signaling associated with food valuation after glucose and sucralose.

Effects of the Daily Consumption of Stevia on Glucose Homeostasis, Body Weight, and Energy Intake: A Randomised Open-Label 12-Week Trial in Healthy Adults

Stevia is a non-nutritive sweetener, providing sweet taste with no calories. This randomised, controlled, open-label 2-parallel arm trial examined the effects of daily stevia consumption on glycaemia in healthy adults. Secondary endpoints included body weight (BW) and energy intake (EI). Healthy participants (n = 28; aged 25 ± 5y, body mass index 21.2 ± 1.7 kg/m²) were randomised into either the stevia group (n = 14)—required to consume a stevia extract daily—or to the control group (n = 14). At weeks 0 and 12, the glucose and insulin responses to an oral glucose tolerance test were measured; BW and EI were assessed at weeks 0, 6, and 12. There was no significant difference in the glucose or insulin responses. There was a significant main effect of group on BW change (F(1,26) = 5.56, p = 0.026), as the stevia group maintained their weight as opposed to the control group (mean weight change at week 12: −0.22 kg, 95%CI [−0.96, 0.51] stevia group, +0.89 kg, 95%CI [0.16, 1.63] control group). The energy intake was significantly decreased between week 0 and 12 in the stevia group (p = 0.003), however no change was found in the control group (p = 0.973). Although not placebo-controlled, these results suggest that daily stevia consumption does not affect glycaemia in healthy individuals, but could aid in weight maintenance and the moderation of EI.

How Does Our Brain Process Sugars and Non-Nutritive Sweeteners Differently: A Systematic Review on Functional Magnetic Resonance Imaging Studies

This systematic review aimed to reveal the differential brain processing of sugars and sweeteners in humans. Functional magnetic resonance imaging studies published up to 2019 were retrieved from two databases and were included into the review if they evaluated the effects of both sugars and sweeteners on the subjects’ brain responses, during tasting and right after ingestion. Twenty studies fulfilled the inclusion criteria. The number of participants per study ranged from 5 to 42, with a total number of study participants at 396. Seven studies recruited both males and females, 7 were all-female and 6 were all-male. There was no consistent pattern showing that sugar or sweeteners elicited larger brain responses. Commonly involved brain regions were insula/operculum, cingulate and striatum, brainstem, hypothalamus and the ventral tegmental area. Future studies, therefore, should recruit a larger sample size, adopt a standardized fasting duration (preferably 12 h overnight, which is the most common practice and brain responses are larger in the state of hunger), and reported results with familywise-error rate (FWE)-corrected statistics. Every study should report the differential brain activation between sugar and non-nutritive sweetener conditions regardless of the complexity of their experiment design. These measures would enable a meta-analysis, pooling data across studies in a meaningful manner.

The Western diet: a blind spot of eating disorder research?-a narrative review and recommendations for treatment and research

Over the last 50 years, in parallel with the obesity epidemic, the prevalence of eating disorders has increased and presentations have changed. In this narrative review, we consider recent research exploring the implications of changing patterns of food consumption on metabolic and neurobiological pathways, a hitherto neglected area in eating disorder research. One of the major changes over this time has been the introduction of ultra-processed (NOVA-4) foods, which are gradually replacing unprocessed and minimally processed foods. This has resulted in the increased intake of various sugars and food additives worldwide, which has important metabolic consequences: triggering insulin and glucose response, stimulating appetite, and affecting multiple endocrine and neurobiological pathways, as well as the microbiome. A paradigm shift is needed in the conceptual framework by which the vulnerability to, and maintenance of, different eating disorders may be understood, by integrating recent knowledge of the individual metabolic responses to modern highly processed foods into existing psychological models. This could stimulate research and improve treatment outcomes.

Effects of Non-nutritive Sweeteners on Sweet Taste Processing and Neuroendocrine Regulation of Eating Behavior

PURPOSE OF REVIEW

Non-nutritive sweeteners (NNS) are increasingly used as a replacement for nutritive sugars as means to quench the desire for "sweets" while contributing few or no dietary calories. However, there is concern that NNS may uncouple the evolved relationship between sweet taste and post-ingestive neuroendocrine signaling. In this review, we examine the effects of NNS exposure on neural and peripheral systems in humans.

RECENT FINDINGS

NNS exposure during early development may influence sweet taste preferences, and NNS consumption might increase motivation for sweet foods. Neuroimaging studies provide evidence that NNS elicit differential neuronal responsivity in areas related to reward and satiation, compared with caloric sweeteners. Findings are heterogenous regarding whether NNS affect physiological responses. Additional studies are warranted regarding the consequences of NNS on metabolic outcomes and neuroendocrine pathways. Given the widespread popularity of NNS, future studies are essential to establish their role in long-term health.

Central nervous pathways of insulin action in the control of metabolism and food intake

Insulin acts on the CNS to modulate behaviour and systemic metabolism. Disturbances in brain insulin action represent a possible link between metabolic and cognitive health. Current findings from human research suggest that boosting central insulin action in the brain modulates peripheral metabolism, enhancing whole-body insulin sensitivity and suppressing endogenous glucose production. Moreover, central insulin action curbs food intake by reducing the salience of highly palatable food cues and increasing cognitive control. Animal models show that the mesocorticolimbic circuitry is finely tuned in response to insulin, driven mainly by the dopamine system. These mechanisms are impaired in people with obesity, which might increase their risk of developing type 2 diabetes and associated diseases. Overall, current findings highlight the role of insulin action in the brain and its consequences on peripheral metabolism and cognition. Hence, improving central insulin action could represent a therapeutic option for people at an increased risk of developing metabolic and cognitive diseases.

Excessive Fructose Intake Impairs Baroreflex Sensitivity and Led to Elevated Blood Pressure in Rats

Hypertension development with an increased intake of added sugar, especially excessive fructose intake, was shown in the National Health and Nutrition Examination Survey (NHANES) data. However, the mechanism underlying blood pressure (BP) elevation with increased fructose intake is still unclear. First, the present study showed that in rats fed 10% fructose for one week, BP and fructose/glucose levels increased in the central and peripheral nervous system. Furthermore, increased fructose intake resulted in an upregulation of fructose concentration in the cerebrospinal fluid. Second, consumption of excess fructose increased serum triglycerides. However, the inhibition of triglyceride production did not mitigate sympathetic nerve hyperactivity, but contributed to an insignificant decrease in BP. Finally, increased fructose intake reduced nitric oxide (NO) levels in the nucleus tractus solitarii (NTS) and reduced baroreflex sensitivity within a week. Collectively, the data suggested that fructose intake reduced NO levels in the NTS and caused baroreflex dysfunction, which further stimulated sympathetic nerve activity and induced the development of high BP.

Effect of flavor on neuronal responses of the hypothalamus and ventral tegmental area

Although it is well known that food intake is affected by the palatability of food, the actual effect of flavoring on regulation of energy-homeostasis and reward perception by the brain, remains unclear. We investigated the effect of ethyl-butyrate (EB), a common non-caloric food flavoring, on the blood oxygen level dependent (BOLD) response in the hypothalamus (important in regulating energy homeostasis) and ventral tegmental area (VTA; important in reward processes). The 16 study participants (18-25 years, BMI 20-23 kg/m²) drank four study stimuli on separate visits using a crossover design during an fMRI setup in a randomized order. The stimuli were; plain water, water with EB, glucose solution (50gram/300 ml) and glucose solution with EB. BOLD responses to ingestion of the stimuli were determined in the hypothalamus and VTA as a measure of changes in neuronal activity after ingestion. In the hypothalamus and VTA, glucose had a significant effect on the BOLD response but EB flavoring did not. Glucose with and without EB led to similar decrease in hypothalamic BOLD response and glucose with EB resulted in a decrease in VTA BOLD response. Our results suggest that the changes in neuronal activity in the hypothalamus are mainly driven by energy ingestion and EB does not influence the hypothalamic response. Significant changes in VTA neuronal activity are elicited by energy combined with flavor.

Brain activity and connectivity changes in response to nutritive natural sugars, non-nutritive natural sugar replacements and artificial sweeteners

INTRODUCTION

The brain plays an important regulatory role in directing energy homeostasis and eating behavior. The increased ingestion of sugars and sweeteners over the last decades makes investigating the effects of these substances on the regulatory function of the brain of particular interest. We investigated whole brain functional response to the ingestion of nutrient shakes sweetened with either the nutritive natural sugars glucose and fructose, the low- nutritive natural sugar replacement allulose or the non-nutritive artificial sweetener sucralose.

METHODS

Twenty healthy, normal weight, adult males underwent functional MRI on four separate visits. In a double-blind randomized study setup, participants received shakes sweetened with glucose, fructose, allulose or sucralose. Resting state functional MRI was performed before and after ingestion. Changes in Blood Oxygen Level Dependent (BOLD) signal, functional network connectivity and voxel based connectivity by Eigenvector Centrality Mapping (ECM) were measured.

RESULTS

Glucose and fructose led to significant decreased BOLD signal in the cingulate cortex, insula and the basal ganglia. Glucose led to a significant increase in eigen vector centrality throughout the brain and a significant decrease in eigen vector centrality in the midbrain. Sucralose and allulose had no effect on BOLD signal or network connectivity but sucralose did lead to a significant increase in eigen vector centrality values in the cingulate cortex, central gyri and temporal lobe.

DISCUSSION

Taken together our findings show that even in a shake containing fat and protein, the type of sweetener can affect brain responses and might thus affect reward and satiety responses and feeding behavior. The sweet taste without the corresponding energy content of the non-nutritive sweeteners appeared to have only small effects on the brain. Indicating that the while ingestion of nutritive sugars could have a strong effect on feeding behavior, both in a satiety aspect as well as rewarding aspects, non-nutritive sweeteners appear to not have these effects.

TRIAL REGISTRATION

This study is registered at clinicaltrials.gov under number NCT02745730.