Diet and Interoception

In this study by Datta et al. (2021), the authors investigate the impact eating disorders induce on interoception in a population of 99 college students, being a particularly vulnerable population to eating disorders and the practice of dieting trends. The participants were divided randomly into two groups, consuming either a high-calorie or a low-calorie shake in the middle of the day. The authors scored participants on eating disorder symptoms using data on their happiness, satiety, energy levels before and after the intervention, their perception of the caloric content of the shake, and mood changes. The authors observed that participants with lower levels of eating concerns felt fuller after consuming the high-calorie shake, while participants who had higher levels of eating concerns felt happier after consuming the high-calorie shake. Participants who ate more freely than their peers were able to guess the caloric content of the shake more accurately depending on how full they felt, however, participants who restricted their dietary intake were unable to do so. The authors conclude that interoceptive abilities could be directly influenced by disordered eating, in addition to the subject’s level of dietary restraint and concerns. The initial data suggests that the inability to comprehend and acknowledge visceral signals more readily could be linked to eating disorder symptomatology and occur at an earlier point in time than expected for this population. [NPID: Appetite, eating concern, interoception, mood, satiety, subclinical]

Even though derangements in the interoceptive signal processing of satiety and hunger play a significant role in abnormal eating behaviors, they continue to be evaluated using general evaluations of interoceptive sensibility (IS; how individuals personally account for their internal physical cues). Generalized measurements of IS include cues from several physiological systems, such as cardiac and gastric cues, thus, in this study by Poovey et al. (2022), the authors attempted to evaluate hunger and satiety-specific IS in a population of 213 participants (mean age = 20.77 years, 50% females). The participants submitted a series of online evaluations to measure IS, including the Multidimensional Assessment of Interoceptive Awareness-2 (general), the Intuitive Eating Scale-2 (hunger/satiety-specific), and the Eating Disorder Inventory Interoceptive Awareness Subscale (general), in addition to the Eating Pathology Symptoms Inventory to evaluate potential eating attitude or behavior derangements in the participants. After controlling for variables, analysis of the results revealed a relationship between hunger/satiety-specific IS and purging, binge eating, and cognitive restraint, demonstrating superior prediction over conventionally used general IS measures. It was noted, however, that hunger/satiety-specific IS could not be used as a predictor of restriction pattern eating behaviors. The authors conclude by discussing how derangements in the interoceptive processing of hunger and satiety signals could present a substantial target for treatment interventions and screening endeavors in the management of disordered eating behaviors, and the significance of selecting appropriate IS measurement methodologies. [NPID: Disordered eating behavior, hunger cues, interoception, satiety cues]

Metabolic disorders, like type 2 diabetes and obesity, impose a looming threat to our well-being and overall health. One of the reasons behind this is the excessive intake of sugars and saturated fats, which are hallmark features of the dietary pattern known as the Western-style diet (WD). In this publication by Davidson & Stevenson (2022), the authors outline the underlying mechanism behind the relationship between WD intake and brain substrate modulations that play a role in interoceptive hunger and satiety signal processing. The authors present current evidence from human and rat studies supporting this theoretical mechanism, demonstrating how the ability of these interoceptive signals to alter eating and appetitive behaviors is dependent on hippocampal learning memory operational coherence, in particular, operations that utilize contextual information in the recall of memories linked to other experiences. Taking this concept in mind, the authors postulate that satiety interoceptive signals halt the reward perception after food intake in animals, regardless of the existence of further food cues or appetitive behaviors, which then become ineffective in recalling memories of reward. The authors comment that these results substantiate that WD intake (with elevated content of sugar and saturated fat) leads to physiological derangements, particularly in the hippocampus, encumbers the ability of interoceptive contextual stimuli of hunger and satiety from controlling dietary behavior, and interferes with hippocampal-dependent learning and memory (HDLM). Finally, the authors postulate that owing to the negative impacts of the WD pattern, a vicious cycle could emerge, potentiating further WD patterns, obesity, and worsening cognitive derangement. [NPID: Eating, inhibition, memory, obesity, satiety]

Interoception (the awareness of a body’s internal states) and the perception and processing of one’s environmental sensory input (exteroception) work in tandem to regulate adaptive behaviors (such as eating) and are linked to the regulation of body weight. In this study by Palazzo et al. (2022), the authors investigated the effect of the Food and Nutrition Education Program with Sensory and Cognitive Exercises on the sensitivity of interoception and exteroceptive perception in a sample of 37 adult women (20-59 years old, BMI between 18.5 and 34.9 kg/m2) who reported difficulties in body weight control. Participants were randomized into two groups and were examined before and after administering the intervention, and before and after a 3-4 weeks waiting period. Data from a heartbeat tracking task helped evaluate interoception, while a writing task describing three foods after tasting them helped evaluate exteroception. The results showed that, following the intervention, participants demonstrated an increase in sensitivity of interoception and in exteroceptive perception. Furthermore, the results revealed a potential relationship between interoceptive mechanisms and exteroception. The authors comment that their work adds to the understanding of perception-promoting strategies and the practice of incorporating physiological and environmental stimuli in food intake. [NPID: Consciousness, exteroception, food education, nutrition education, interoception, nutritional trial, text production]

Interoception is the conscious process through which one acknowledges, formulates, and incorporates internal signals coming from one’s body. Lack of interoception has been associated with higher BMI scores and contributions to gaining weight, however, the resultant findings from investigating such associations have been at odds, and the links between higher BMI and interoceptive deficits remain unclear, in particular, regarding the accuracy of interoception (detection of signals) and sensibility (recognizing and acting upon internal signals). In this systematic review and meta-analysis by Robinson et al. (2021), the authors examined 87 studies looking at the links between interoception and BMI in children and in adults, measuring 121 effects in 10,425 participants, revealing cross-sectional association evidence of higher BMI with interoceptive deficits. Thus, the authors conclude that cross-sectional studies prove the existence of a link between interoceptive deficits and higher BMI, however, the authors comment that the evidence remains inconclusive on whether these deficits contribute to weight gain and obesity, or if they are a result of weight gain and obesity. [NPID: Neuroscience, risk factors, interoception, BMI, weight gain, obesity]

Interoception, defined as the awareness and recognition of internal body signals, is a potentially modifiable contributor to appetite regulation and weight gain. In this study by Robinson et al. (2021), the authors investigate how the relationship between the degree of self-reported interoception and BMI is described through eating behavioral traits. 1,181 participants (49% female, 53% overweight/obese) submitted validated self-reports on interoception measures, dietary habits guiding satiety signals, feedback eating (intuitive eating), emotional over-eating, and several other eating traits. Analysis of the results demonstrated that poor interoception was significantly associated with high BMI, which is explained by how individuals who have poor interoception were less responsive to satiety signals when eating. In addition, the results demonstrated a degree of evidence supporting the finding of how individuals with poor interoception were more likely to indulge in emotional overeating, which further explained how poorer interoceptive accuracy is linked to higher BMI. In conclusion, the authors comment that a lack of interoception could obstruct satiety signal perception, which becomes integral to an individual’s dietary habits and decision making, and ultimately plays a role in elevating BMI. [NPID: Adult eating behaviour, BMI, interoception, intuitive eating, obesity]

According to this 2019 article, overeating and weight gain may be attributed to difficulties in emotional regulation and limited awareness of one’s internal state (interoception). The objective of this study was to examine the emotional governance difficulties and interoceptive deficits in obesity. The researchers also aimed to compare these features between moderately and severely obese patients. Firstly, the 165 participants were categorized into 3 groups according to their body mass index. Each group (severely obese, moderately obese, and normal weight) consisted of 55 subjects. Results indicated that obese patients had more emotional regulation issues and less interoceptive awareness than the normal-weight patients. Moreover, they were less likely to plan strategies, had less emotional awareness, and were less able to observe, notice and trust body sensations. There was no significant difference in results between the moderately and severely obese participants. To conclude, emotional control and interoceptive consciousness should be targeted among obese people, regardless of their BMI. [NPID: interoception, internal state, emotional regulation, emotions, awareness, BMI, obesity, obese]

This 2020 study explains that mindfulness (the practice of non-judgmental awareness of present experience) has been linked with reduced eating psychopathology and emotion-driven eating. Thus, this study set out to find out whether dispositional mindfulness is also related to diet quality. A sample of 406 adults agreed to provide ratings of their dispositional mindfulness, depressive symptoms, perceived stress, positive affect, and negative affect. Greater dispositional mindfulness was associated with higher diet quality (assessed using a food questionnaire). This positive relationship between mindfulness and diet quality was mediated by lower depressive symptoms. Furthermore, dispositional mindfulness was found to positively correlate with positive affect but inversely interact with negative affect and perceived stress. This article concludes that dispositional mindfulness may be related to diet quality among midlife adults. Since lifestyle behaviors in midlife can help predict risk of future cardiovascular disease and cognitive dysfunction, interventions designed to enhance mindfulness may lower disease risk. [NPID: mindfulness, interoception, psychology, depression, emotional eating, diet, diet quality, stress, positive affect, negative affect, positivity, negativity]

Wu et. al (2020) studied the anterior insular cortex (aIC) which integrates interoceptive states and emotional awareness and consequently guides behavioral responses. This experiment on mice demonstrated that the right side aIC CamKII+ (aICCamKII) neurons, when hyperactivated, attenuated food consumption, whereas in the case that they are inhibited feeding increases and the anorexia and weight loss induced initially by neural activation was reversed. Similar manipulation at the left-side aIC did not cause significant behavioral changes. The reason appears to be that aICCamKII neurons project directly to the vGluT2+ neurons in the lateral hypothalamus (LH) while the right-side aICCamKII-to-LH pathway mediates feeding suppression. This study revealed the existence of a circuit from the cortex to the hypothalamus that senses aversive (causing strong dislike) visceral signals and controls feeding behavior. [NPID: interoception, interoceptive awareness, emotional awareness, eating disorders, hypothalamus, visceral signals]

This 2019 study assessed the involvement of the anterior insular cortex (AIC), which mediates interoceptive attention (attention towards physiological signals arising from the body), in interoceptive attention in healthy subjects. The necessity of the AIC in interoceptive attention was also tested by recruiting patients with AIC lesions. Interoceptive attention was determined by using functional magnetic resonance imaging while a novel task was employed - one that directs attention towards breathing rhythm. The results indicated interoceptive attention was associated with increased activation of the AIC. Moreover, the enhanced coupling between the AIC and somatosensory areas, as well as the reduced coupling between the AIC and visual sensory areas were observed. AIC activation was predictive of individual differences in interoceptive accuracy. Importantly, the study found that interoceptive accuracy and sensitivity was disrupted in patients with AIC lesions, providing compelling evidence that the AIC indeed plays a critical role in interoceptive attention.[NPID: interoception, interoceptive awareness, insula, anterior insular cortex, AIC, interoceptive attention, insula lesions, breathing rhythm, interoceptive accuracy]

Kleckner et. al (2017) here introduces a system, conceptually similar to the large-scale intrinsic brain system involving senses such as sight and hearing for example, to represent sensations from within the body known as interoception. The group of researchers behind this study also relate this system with the regulating peripheral systems in the body called allostasis. The existence of an intrinsic allostatic/interoceptive system in the brain was evaluated using tract-tracing studies of macaque monkeys, two magnetic resonance imaging samples totalling 550 entries, and a new Embodied Predictive Interoception Coding (EPIC) model. After evaluating another sample of 41, it was proven that individuals with stronger connectivity between system hubs performed better in terms of interoceptive ability. Kleckner et. al (2017) provide new insights for the brain’s functional architecture and claims to have possibly united mental and physical illness. [NPID: interoception, interoceptive awareness, allostasis]

Hargrave et. al (2016) explains that one of the roles of the hippocampus is to inhibit responding to previously rewarded cues with the use of context such as interoceptive satiety states. Constantly consuming during states of positive energy balance leads to weight gain and obesity. Research has implicated Western diets in several types of hippocampal dysfunction including reduced expression of neurotrophins (induce neural survival, development and function) and nutrient transporters, increased inflammation, microglial activation (involved in immune response), and blood brain barrier permeability. Since hippocampal dysfunction is associated with an animal’s inability to modulate responding to previously reinforced cue, this paper proposes that such deficits promote overeating, which can exacerbate hippocampal impairment, and start a vicious cycle of obesity and cognitive decline. [NPID: interoception, interoceptive awareness, hippocampus, reward, satiety, weight gain, obesity, Western-style diet, inflammation, microglial activation, blood brain barrier, hippocampal dysfunction, overeating, cognitive decline]

Critchley & Garfinkel (2017) believes our understanding of emotions and its disorders is growing thanks to greater comprehension of interoception, which means the afferent signalling (mode in which stimuli is sent to the brain), central processing, plus internal body signals interpreted in mental and neural form. The authors describe the new insights discovered concerning interoception and the way it contributes to emotion. They include short-term interoceptive effects on neural and mental processes, the recognition of distinguishable psychological aspects of interoception, and models that explain emotions and selfhood (social construction of self). [NPID: interoception, interoceptive awareness, emotion, afferent signaling, self, selfhood, social construction of self]

Stevenson, Mahmut & Rooney (2015) examined whether there are individual differences in several aspects of and possible causes of ingestion-related interoception (ability to perceive internal bodily states) such as signals from the viscera, motivational states, affective reactions, as well as associated cognitions. Individual variation in almost all aspects of interoception was documented for hunger, fullness and thirst - including how participants use, prioritise and integrate visceral, motivational, affective and cognitive information. The review found variation between individuals may arise from multiple causes, including genetic influences, developmental alterations thought to possibly result from child feeding practices, and from conditions such as depression, anxiety, eating disorders and certain subtypes of obesity. Ingestion-related interoception could also be affected by diets with low nutritional value and dietary restraint. The practical and theoretical consequences of these individual differences are discussed in this review. Stevenson et. al (2015) stated that certain forms of brain injury (notably to the temporal lobes) are associated with impaired ingestion-related interoception. [NPID: interoception, interoceptive awareness, viscera, motivational states, individual variation, depression, anxiety, eating disorders, obesity, child feeding practices, temporal lobes]

In this study undertaken in 2019, the aim was to quantify the dynamics of different post-ingestive sensations after eating as well as to study the effect of protein and carbohydrate on hedonic (pleasant/unpleasant) and post-ingestive responses. Using a randomised controlled crossover design, forty-eight participants (mean age 20.4) had a high in protein (HighPRO) or high in carbohydrate (HighCHO) breakfast on two separate days. Post-ingestive sensations were then reported every 30 minutes for three hours following consumption. The results indicated HighCHO, in comparison to HighPRO, induced greater hedonic responses and scored higher ratings for post-ingestive sensations such as satisfaction, food joy, overall wellbeing, and fullness. Although, HighPRO achieved higher ratings for sweet desire post intake. Also a significant main effect of time was demonstrated for all post-ingestive sensations. The study proposes the development of sensations post-meal might be crucial for the consumers’ food choices and for extra calorie intake. [NPID: interoception, interoceptive awareness, hedonic, post-ingestive sensations, satisfaction, food joy, overall well-being, fullness]

Deurland et. al in 2020 conducted these two in-country consumer studies to compare Chinese and Danish consumers in their post-ingestive drivers of Post-Ingestive Food Pleasure (PIFP), which was defined as a “subjective conscious sensation of pleasure and joy experienced after eating”. The post-ingestive sensations and PIFP of the 48 participants from Denmark and the 53 from China were measured for three hours following consumption of a breakfast meal. Key results revealed perceived Satisfaction, Mental, Overall and Physical wellbeing to be highly influential on PIFP in both countries. The Danish consumers, in particular, perceived appetite-related sensations such as satiety, hunger, desire-to-eat and in-need-of-food to be influential on PIFP. Whereas in China, drivers of FIPF were more vitality-related sensations like energised, relaxation and concentration. There were similarities but also distinct subtleties in the cultural constructs of PIFP in Denmark and in China. Deurland et. al (2020) concluded that food pleasure as a post-ingestive measure provides valuable output. [NPID: interoception, interoceptive awareness, China, Danish, pleasure, vitality, energy, relaxation, concentration, Denmark]

Stevenson & Francis (2017) reviewed known, suspected and newly hypothesised hippocampal-dependent functions involved in regulating food intake and for each, evidence was presented for hippocampal involvement, its putative regulatory role was described, and hypothesised effects of hippocampal impairment were also discussed. These functions dependent on the hippocampus of the brain included: declarative memory processes, and their use in explicitly evaluating when, what and how much to eat; interoception, (since it relates to hunger, fullness and thirst); inhibitory processes and their role in modulating memory retrieval; craving and imagery for food; perception of time and its involvement in the preparation of the body for food consumption and estimating meal length; trace conditioning and nutrient-related learning; and inhibition of the hypothalamic-pituitary-adrenal stress response and stress-related eating. It was concluded that the hippocampus is involved in the regulation of food intake via multiple interconnected pathways, many of which are either understudied or not studied yet. [NPID: interoception, interoceptive awareness, hippocampus, memory, hunger, fullness, thirst, meal length, stress]

Sample et. al (2015) addresses the “obesogenic environments” commonly found in the western and westernised societies and the hypothesis that the external cues (that characterise obesogenic environments) associated with highly palatable, energy-dense foods may elicit such powerful changes in appetitive and eating behavior that the internal physiological mechanisms that helps maintain energy balance may become overwhelmed. Sample and others (2015) therefore undertook two experiments to investigate a learning mechanism that may underlie the supposed loss of internal control (relative to external). The first experiment involved rats provided with external stimuli (auditory cues) and varying levels of food deprivation (internal stimuli), both of which could be used to solve a simple discrimination task. Yet, deprivation cues ended up gaining substantial discriminative control over conditioned responding. Whereas, experiment 2 found that in comparison to standard chow, maintenance on a "western-style" diet high in saturated fat and sugar weakened discriminative control by food deprivation cues, but did not impair learning when external cues were also trained as relevant discriminative signals for sucrose. The researchers concluded that eating a western-style diet contributed to a loss of internal control over appetitive behavior relative to external cues, and discussed how interference of hippocampal-dependent learning and memory processes may be the cause of this relative loss of control by food deprivation signals. This would form the basis of a vicious-cycle of excessive consumption, body weight gain, and progreesive cognitive decline that could begin “very early” in life. [NPID: interoception, interoceptive awareness, body image, internal control, control, HDML, hippocampus, Western-style diet, WS diet, cognitive decline]

Since there have been suggestions that interoception (perception of bodily signals) and interoceptive sensitivity (sensitivity for internal signals) might play crucial roles when it comes to regulation of behavior associated with feelings of satiety, Herbert & Pollatos (2014) examined interoceptive sensitivity among 75 overweight and obese women and men (using a heartbeat detection task) and compared them to normal weight controls. The hypothesis before the initiation of the study that overweight and obese would be related to attenuated interoceptive sensitivity was proved right, with evidently higher scores seen for those normal weight participants compared to overweight + obese. In addition, a negative correlation was identified between the BMI and interoceptive sensitivity in the overweight and obese groups only. In the conclusion section, Herbert and Pollatos (2014) writes that presumably, interoceptive sensitivity interacts with the regulation of food intake in everyday life in part by promoting the detection of bodily changes accompanying satiety, the signals of which may be poorly detected by overweight and obese individuals. [NPID: interoception, interoceptive awareness, interoceptive sensitivity, heartbeat detection task, obesity, satiety]

Young et. al (2017) designed two studies both on eating behavior and interoception since “at present it is unclear which aspects of interoception contribute to aberrant eating behaviour and obesity”. The first study used the novel interoceptive indices [interoceptive metacognitive awareness (IAw) and interoceptive prediction error (IPE)] and the traditional measures such as interoceptive accuracy (IAc) and interoceptive sensibility (IS), and examined their links with eating behavior and body mass index (BMI). The results confirmed the dissociation between these interoceptive indices: emotional eaters were characterised by a heightened interoceptive signal but reduced mega-cognitive awareness of their interoceptive abilities; and emotional eating was found to correlate with IPE but this effect could not be accounted for by differences in anxiety and depression. The second study verified the positive association between interoceptive accuracy and emotional eating using a new non-biased heartbeat discrimination task (based on the method of constant stimuli). The findings from study two included new and important mechanistic insights into the processes that may underlie problematic affect regulation in those overweight. [NPID: interoception, interoceptive awareness, obesity, metacognitive awareness, interoceptive prediction error, emotional eating, anxiety, depression, heartbeat discrimination task]

This 2016 study explored the possible association between interoceptive awareness with performance on a hippocampal dependent learning and memory (HDLM) measure in logical memory percent retention, among healthy young adults. Interoceptive awareness was assessed on three tasks: heart rate tracking; water loading and the Multidimensional Assessment of Interoceptive Awareness Questionnaire (MAIA). After controlling for potentially confounding variables, significant associations were revealed between HDLM performance and MAIA measures as well as water loading. These results implicate the role of hippocampal dependent processes in interoceptive awareness in healthy young adults, and may suggest the medial temporal lobe structures regulate interoceptive tasks (which includes ingestion). [NPID: interoception, interoceptive awareness, ingestion, HDLM, hippocampal dependent learning and memory, HDLM, heart rate tracking, water loading, medial temporal lobe]

Stevenson, Mahmut & Rooney (2015) examined whether there are individual differences in several aspects of and possible causes of ingestion-related interoception (ability to perceive internal bodily states) such as signals from the viscera, motivational states, affective reactions, as well as associated cognitions. Individual variation in almost all aspects of interoception was documented for hunger, fullness and thirst - including how participants use, prioritise and integrate visceral, motivational, affective and cognitive information. The review found variation between individuals may arise from multiple causes, including genetic influences, developmental alterations thought to possibly result from child feeding practices, and from conditions such as depression, anxiety, eating disorders and certain subtypes of obesity. Ingestion-related interoception could also be affected by diets with low nutritional value and dietary restraint. The practical and theoretical consequences of these individual differences are discussed in this review. Stevenson et. al (2015) stated that certain forms of brain injury (notably to the temporal lobes) are associated with impaired ingestion-related interoception. [NPID: interoception, interoceptive awareness, viscera, motivational states, affective reactions, cognition, hunger, fullness, thirst, depression, anxiety, eating disorders, brain injury]

Quadt et. al (2018) presented a neurobiological overview of interoception (the sensing of internal bodily sensations) and described how interoceptive impairments at different levels relate to specific physical and mental health conditions (such as sickness behaviors and fatigue, depression, eating disorders, autism, and anxiety). This review shows that systematic investigation of how individual differences, and within-individual changes, in interoceptive processing can contribute to the mechanistic understanding of physical and psychological disorders. The findings were framed in an interoceptive predictive processing framework and highlight potential new avenues for treatments. [NPID: interoception, fatigue, depression, eating disorders, autism, anxiety, psychological disorders]

This study published in 2017 investigated the impacts of briefly consuming a high fat with high sucrose (HFS) diet over 4 days relative to one lower in saturated fat and added sugar, on hippocampal-dependent learning and memory (HDLM) and perception of internal bodily state (interoception). A group of healthy individuals were randomly assigned to either the Experiment condition (HFS breakfast) or the control condition, and were assessed before and after breakfast on day one and four on HDLM, interoception and biological measures. Food diaries were also completed before and during the study. The results showed significant reductions in HDLM and reduced interoceptive sensitivity to hunger and fullness among the Experimental condition group, in comparison with the control group. The greater reductions in HDLM was associated with the larger changes in blood glucose across breakfast. Those assigned to the experimental condition exhibited markedly different blood glucose and triglyceride responses to their breakfast relative to the control group. The Experimental condition compensated for their energy-dense breakfast by reducing carbohydrate intake, while saturated fat intake remained consistently higher than Controls. Attuquayefio et. al (2017) claims to have replicated the results of animal studies in humans in the way a Western-style diet impacts HDLM, and concludes that the link between diet-induced HDLM changes and blood glucose suggests one pathway by which diet impacts HDLM in humans. [NPID: interoception, high fat, high sugar, HDLM, hippocampal-dependent learning and memory, hippocampus, food diary, interoceptive awareness, blood glucose, glucose, carbs, Western-style diet, WS diet]