Diet and Psychosocial

Perceived social isolation has been linked to several negative health outcomes, such as obesity, alterations in eating behaviors, and psychological symptoms. However, the neural mechanisms governing these associations remain unclear. In this study by Zhang et al. (2024), the authors conducted a cross-sectional analysis to explore this relationship using a sample of healthy, premenopausal female participants, aiming to assess brain reactivity to food cues, eating behaviors, obesity, and mental health symptoms. While engaging in a food cue viewing task, functional magnetic resonance imaging (fMRI) examined the participants. Analysis of the results from 93 participants revealed that higher perceived social isolation was associated with increased fat mass percentage, poorer diet quality, and elevated maladaptive eating behaviors, such as cravings and food addiction. Additionally, participants reported higher levels of anxiety, depression, and reduced psychological resilience. Analysis of brain imaging data demonstrated that higher social isolation leads to alterations in neural responses to food cues in regions associated with executive control, internal appetite regulation, and visual attention networks. Notably, changes in neural responses to sweet foods were linked to various psychological symptoms and maladaptive eating behaviors. These altered brain responses mediated the relationship between social isolation and negative health outcomes, including diminished positive affect and increased body fat composition. The authors comment that their findings highlight the impact of social isolation on the neural processing of food cues and its implications for eating behaviors, obesity, and mental health. The study emphasizes the importance of comprehensive interventions targeting both mind and body to address the adverse effects of social isolation on health. [NPID: Perceived social isolation, negative health outcomes, altered eating behaviors, obesity, psychological symptoms, brain reactivity, food cues, maladaptive eating behaviors, mental health]

Research has shown correlations between food, eating habits, loneliness or social isolation, and significant health repercussions. Dietary habits and loneliness are acknowledged as health factors that should be the focus of individual, group, and population-level interventions. However, the level of evidence evaluating such connections remains insufficient. In this scoping review, Hanna et al. (2023) compiled a body of research examining the relationship between eating and food habits and feelings of loneliness or social isolation in those over 16 years of age. Utilizing predefined search criteria, five databases from 2000 were systematically searched. Following a full text screening of 254 publications and theses, three qualitative and 26 quantitative studies—eight of which were carried out during COVID-19 lockdowns—were included in the analysis. The authors noted that nearly all studies found a link between unhealthy eating habits, having a lower-quality diet and consuming fewer fruits and vegetables etc.), and and feelings of loneliness and social isolation. The harmful effects of social isolation or loneliness on eating were also supported by qualitative studies examined. The authors highlight that employing different analytical approaches made it more challenging to evaluate and compare the results despite considering study quality. Finally, the authors conclude that policymakers, researchers, nutrition and mental health practitioners, and end users must be better informed about the intricate relationships between these many facets of health to design treatments and practices. [NPID: Loneliness, social isolation, food, nutrition, eating behaviours, diet]

It is unknown whether elevated obesity-related mortality risk could be attenuated by improvements in social isolation and loneliness, conditions that are substantially more prevalent in obese people than in non-obese people. Zhou et al. (2024) sought to find out if a reduction in social isolation or loneliness would decrease the excess mortality risk associated with obesity. In this cohort research, participants were recruited from the UK Biobank who were free of cardiovascular disease (CVD) or cancer at baseline. Follow-up for the participants lasted from March 2006 to November 2021. Mortality resulting from cardiovascular disease, cancer, and all causes were evaluated. The study included 398972 individuals (mean [SD] age: 55.85 [8.08] years; 220469 [55.26%] women; 13734 [3.44%] Asians; 14179 [3.55%] Multiracial; and 363685 [91.16%] White people). 305615 (76.60%) did not suffer from obesity, and 93357 (23.40%) were obese. Twenty-two thousand eight hundred seventy-two incident fatalities were documented over a median (IQR) follow-up of 12.73 (12.01-13.43) years. Data Analysis demonstrated a significant increase in all-cause mortality in obese individuals with a social isolation score of 2 or higher compared to their peers who scored 1 or 0. Similarly, obese individuals with a score of 2 or higher on the loneliness index had a significant increase in all-cause mortality compared to their peers who scored 1 or 0. Multivariate data analysis demonstrated that when the social isolation and loneliness score moved from highest to lowest, a reduction in all-cause mortality by 36% and 9%, respectively, was observed in individuals with obesity compared with those without obesity. When calculating the risks of all-cause mortality, cancer-related mortality, and CVD-related mortality, social isolation ranked higher than depression, loneliness, anxiety, and lifestyle-related risk factors, including alcohol, physical activity, and a balanced diet. The authors conclude that a lower index of social isolation or loneliness was linked to a lower risk of all-cause mortality in obese individuals in this population sample from the UK Biobank. An improvement in social isolation and loneliness was shown to reduce the extra risk of all-cause mortality associated with obesity. [NPID: Social isolation, loneliness, mortality, excess mortality risk, obesity, adults]

In this cross-sectional study by Vogt & Gustafsson (2022), the authors aimed to investigate whether the known inequalities in the intake of fruits and vegetables are influenced by social identities and social status, namely, gender and education. To do so, the authors used data from the 2018 Health on Equal Terms survey (northern Sweden), providing information on a total of 21853 participants. The authors categorized the data according to gender and education (high/low educational attainment, men/women) and investigated three possible outcomes: lower intake of both fruits and vegetables, of vegetables alone, or fruits alone. Analysis of the results revealed that educated women had the highest probability of consuming adequate amounts of fruits and vegetables, separately or in combination, while uneducated men had the highest likelihood of reduced intake in all three categories. Further analysis revealed that the differences observed between educated women and uneducated men are explained by inequalities in gender and education, as other excess intersectional disparities existing beyond gender and education were not sufficient to account for the observed results. The authors conclude that these results demonstrate the need for targeted policies and intervention methods aimed at dietary inequality for vulnerable groups, in addition to a universal approach, thus improving overall efficiency. [NPID: Intersectionality, joint disparity, referent disparity, excess intersectional disparity, fruits, vegetables, discriminatory accuracy, gender, education, Sweden]

Dietary intake is subject to a myriad of influencers, and amongst those relates to the social setting related to a meal, namely, the presence of familiar individuals. In other words, we tend to eat more food than usual if we eat together with friends or family. As the reasons behind this observation remain not well understood, Ruddock et al. (2021) conducted a couple of studies to investigate the social impact on food consumption. In their first study, the eating behavior of 98 participants (females, average age of 20 years) was observed after allowing the participants access to food and separating them into two groups, depending on the timing of food serving relative to social interaction (whether the participants ate alone or with a friend). In their second study, the authors observed the changes in serving size depending on whether the meal was shared with a friend or with a stranger, in a sample of 120 participants (females, average age of 19 years). In both studies, the authors observed a substantial increase in the amount of food served and consumed in familiar social settings (i.e., eating with friends) compared to eating alone or with a stranger. The authors comment that their findings demonstrate the impact of social interaction on the amount of food we consume, and therefore the necessity to reconsider current viewpoints on the social impact of dietary behavior. [NPID: Human behavior, eating, portion size, eating alone, eating with family, friends]

Social settings associated with eating meals appear to influence the amount of food consumed. In other words, eating with strangers raises the odds of consuming less food compared to eating with family and friends, which was found to increase the amount of food consumed. This is known as the social facilitation of eating. Higgs et al. (2022) conducted two studies to evaluate social facilitation and inhibition awareness, where 481 participants in their first study were asked to picture a dining scenario and account for whether they would eat more food, less food, or eat the same amount they’re accustomed to, if they were to eat with someone who they are more familiar or less familiar with, such as a stranger, acquaintance, family member or friend, compared to the amount of food they would eat if they were dining alone. Analysis of the participant responses in study 1 revealed that participants envisioned themselves eating a special meal with family members or friends, with a substantial majority accounting that they would consume less food if they are dining with strangers or acquaintances and that they would consume the same amount of food or eat more food if dining with family or friends. The authors’ second study (485 participants) echoed similar dining perceptions to study 1, however, the latter participants reported their perceptions to include both special and regular meals. The majority of study two’s population reported eating less in special or regular meals if they were dining with strangers, and eating the same amount of food they’re accustomed to if they would be having regular meals with acquaintances. However, if special meals are involved, the participants were equivocal on eating less or eating the same amount of food. Most participants reported that they would eat more food when having a special meal with family or friends, but would eat the same if they were having a regular meal. The authors highlight that the investigated participants are aware of the social facilitation and inhibition behaviors that are involved when having special meals, however, the participants fail to recognize or admit that eating with family or friends causes them to eat more food in comparison to having meals on their own. The authors conclude that enhancing the perception of individuals on this aspect of dietary intake in the company of family or friends can help individuals trying to regulate their consumption of food. [NPID: Awareness, eating, social facilitation, social influences, social inhibition]

This 2019 review highlights how couples’ relationships, partners’ individual and joint vulnerabilities, and their health behaviors can influence health through changes in gut microbiota, metabolism, and immune function. When couples share stressors and emotions in their commonly intertwined lives, these partners may be at risk of common disease partly due to parallel alterations in their gut microbiota. Marital discord, stress, and depression can all fuel one another. Additionally, chronic marital stress and depression can make partners susceptible to obesity, metabolic syndrome, and cardiovascular disease through changes in resting energy expenditure, insulin production, and triglyceride responses after unhealthy meals. During stressful periods, one can become less active, develop sleeping problems, and adopt poor eating habits, all of which can promote gut dysbiosis (imbalance of the bacterial community) and affect metabolic pathways. This loss of balance in bacterial communities can increase intestinal permeability (gut leakiness) and can potentially be involved in the increase in inflammation and acceleration of aging. Age-related changes in the gut microbiota's composition and gut leakiness can facilitate age-related immune dysfunction and inflammation. The risk of developing these age-related conditions may be influenced by depression, diet, sleep, exercise habits, and emotion control strategies. Since partners can affect each other’s moods and behaviors, this article presents a novel way of viewing the health implications of marriage. [NPID: marriage, married, couples, partners, relationships, health, gut, GI, gastrointestinal, mood, immune system, immunity, gut microbiota, gut health, gut bacteria, depression, lifestyle, aging, stress, diet, exercise, sleep]

The elderly population faces unique dietary challenges. For example, the influence of factors such as a companion’s physical presence on eating and cardiovascular health in a geriatric population remains poorly understood. Thus, Han-Gyo et al. (2022) set out to investigate potentially existing differences in health habits, nutrition, and the odds of suffering from cardiovascular diseases or the presence of cardiovascular disease risk factors with respect to the presence of an eating companion in 590 menopausal women aged ≥65 years. Participants who had three or more meals a day by themselves were categorized into an eating-alone (EA) group, while participants who had companions for three or more meals a day belonged to an eating-with-others (EO) group. This cross-sectional study revealed that the EA group members were less likely to pay attention to, or use, nutrition labels, ate fewer carbohydrates, fiber, sodium, and potassium, had an overall lower energy intake, and suffered higher odds of experiencing cardiovascular symptoms such as angina, compared to the EO group. The authors demonstrated that if elderly women ate their meals alone, they exhibited limited nutritional knowledge and consumption, and were more likely to experience cardiovascular symptoms such as angina. The authors conclude that providing education focused on nutrition and screening for cardiovascular disease in elderly women who mainly eat alone is highly recommended. [NPID: Elderly women, cardiovascular disease, eating alone, nutrients, menopause, loneliness]

This 2020 study tries to address the limited evidence on the effect of social contexts on people’s food choice. This experiment tested the extent to which disadvantageous social contexts influence food choice in healthy, non-dieting participants. Three established experimental methods were used to create social contexts such as giving the subjects varying amounts of money in a Dictator game. Another group of participants were included or excluded from a Cyberball game, while 81 individuals took part in a response time ranking task. The sample groups were then provided with a choice of food items ranging in perceived tastiness and healthfulness. Just like a previous study, those with strong dispositional self-control (as indicated by the questionnaire) were more likely to choose healthier foods. Moreover, people who were unfairly treated in the Dictator game, excluded from the Cyberball game, or performed poorly in the task ended up with negative emotions, as predicted. However, there was no evident effect of the social contexts on food choice among the sample in any of the experiments. The results suggest that disadvantageous social contexts have negligible impact on food choice, at least it appears to under laboratory setting. [NPID: social contexts, social factors, social influence, social, perception, diet, food choice, healthy eating, self-control]

Several studies have proposed that probiotics may be able to ameliorate symptoms of anxiety. However, the literature examining the relationship between probiotics and social anxiety remains insufficient. To determine whether eating fermented foods that may contain probiotics would consort with neuroticism (i.e., the disposition to experience negative emotions) and thereby impact experienced symptoms of social anxiety, Hilimire, DeVylder, and Forestell (2015) studied self-reported data outlining eating fermented food, neuroticism, and social anxiety in a sample of 710 adults. The authors’ interaction model, accounting for participant demographics, healthy food consumption, and exercise, demonstrated that participants’ exercise habits, neuroticism, and the frequency of eating fermented food were significant predictors of social anxiety. In detail, the model showed that participants with high neuroticism who ate more fermented food were less likely to report symptoms of social anxiety. In agreement with previous works, the authors have shown that consuming fermented foods containing probiotics may provide a level of protection from experiencing social anxiety symptoms in individuals with a higher genetic predisposition to anxiety, providing a possible low-risk intervention. The authors conclude that further research is paramount to explore the dynamics behind the effect fermented foods have on our experience of social anxiety. [NPID: Fermented foods, exercise, neuroticism, probiotics, social anxiety disorder, social phobia]

This 2012 study identified the lack of research examining whether social factors affect ratings for food and drink liking. Two experiments were carried out to test whether instilling the belief that others don’t like a food item influences the individual’s evaluations for food liking. In the first study, participants were exposed to a variety of different social normative information. For example, one group was led to believe that other group members dislike orange juice, while another group may have been manipulated to think that other groups dislike orange juice. Within another third group, it was suggested that the group members were neutral about orange juice. In this first study, the participants’ likings for the orange juice were influenced only by information on social norms involving members of the same group. In study 2, subjects ate a snack food before finding out that two previous participants had either liked or disliked the food. The revelation that others had negative experiences with the food resulted in decreased liking scores for the food. Social influence was evident across both studies. [NPID: social norms, social influence, foods, eating, perception, behaviors, psychosocial, psychology, diet]

Although social norms are believed to influence eating behavior, this 2015 article highlights that few studies have investigated the underlying mechanisms of this conformity. Thus, this study tested whether group norms can change people’s preferences for foods at both behavioral and neural levels. Firstly, hungry participants were asked to rate their preferences for various healthy and unhealthy foods. Then, each subject was shown what appeared to be the ratings of others, which were all either higher, lower than, or the same as the participants themselves. Everyone was then asked to provide ratings again. The second ratings were found to resemble that of their peers’. This consensus with peers caused greater activity in the nucleus accumbens (a brain region associated with reward prediction errors) when compared with disagreement. The strength of this brain activity predicted the extent to which subjects’ ratings conformed to that of their peers, suggesting that the value associated with consensus drives social influence. Moreover, the brain region called the ventromedial prefrontal cortex (vMPFC) initially responded more strongly to unhealthy foods, compared with healthy foods. However, this effect was overwritten after participants gathered information on others’ likings and popularity of the foods. Overall, these results suggest that group norms can shift food preferences, and that norms-based interventions can be utilized to promote healthy eating habits. [NPID: healthy eating, diet, nutrition, psychology, perception, behaviors, norms, group norms, social norms, preferences, healthy foods]

While there are many studies that suggest that social eating norms strongly influence both food choice and consumption, this 2015 review outlines the possible reasons why people follow social eating norms and investigates the moderating factors involved in norm-following. Higgs firstly suggests that eating norms are followed because it promotes the sharing of food, and spreads information about safe foods. Norms are effective in affecting human behavior since following these norms is connected with social judgment. It was stated that people are more likely to follow norms when there is a sense of uncertainty around what is the correct or incorrect behavior. Norm-following then allows individuals to feel a sense of shared identity with the person/group they mimicked. It is the modification of self-perceptions and sensory or hedonic (pleasure-related) assessments of food caused by social norms that may affect food choice and level of intake. And it is likely that people’s following of eating norms is reinforced by the same neural systems responsible for mediating the rewarding aspects of food. [NPID: psychosocial, social norms, food sharing, behavior, social judgement, shared identity, sensory, hedonic pleasure, pleasure, hedonic, food choice, decision making, reward]

This 2016 study aimed to find out how certain messages and conditions can affect food intake from a buffet in both low- and high-consumers of vegetables. Several factors were investigated, including the impact of the liking norm (where information about others' liking for a food is known). Immediate food selection was examined as well as food choices 24 hours after exposure. Other conditions included descriptive norm (effect of others’ behaviors), health message, vegetable variety condition, and neutral control message. The food buffet consisted of three raw vegetables, three energy-dense foods, and two dips. Although there was a link identified between the message condition and habitual vegetable consumption, there was no indication of significant effects in the follow-up tests. Looking at each food individually, there was an interesting interaction involving broccoli. Participants who normally did not previously eat high amounts of vegetables showed increased intake of broccoli in the vegetable variety and liking norm conditions (when others demonstrated their liking), when compared with themselves in the neutral control condition. This study encourages further analysis of the liking norm and vegetable variety conditions, and their influence on vegetable intake. [NPID: diet, vegetables, nutrition, liking norm, perception, influence, behavior, food choice, raw vegetables]

In this 2017 study, a poster featuring a social norms-based message was placed in restaurants in the United Kingdom to assess what impact it has on purchases of vegetable-containing meals and whether an increase in sales can be sustained. The intervention phase, where the posters containing social norm messages relaying information about vegetable purchases at other restaurants were placed in each of the 3 restaurants, lasted 2 weeks, with 2 weeks either side of this phase called the pre-intervention phase and post-intervention phase. The analysis using Pearson’s chi-squared test revealed 57% of the participants were male, 75% were not overweight, and 98% were under 60 years of age. The social norm-based message was positively associated with the percentage of meals purchased with vegetables, with 60% of purchases containing vegetables at baseline, 64% during the 2-week intervention phase, and still 67% post-intervention. This investigation concludes that social norm messages may increase the purchase of vegetable meals in workplace settings. [NPID: psychosocial, social norms, United Kingdom, intervention, vegetables, vegetable intake, workplace nutrition, workplace]

Stok et. al (2016) assessed the role that peer social norms play in shaping young people’s food intake in this systematic review, breaking down important questions such as whom and when peer social norms are related to the amount of food young people consume. A total of thirty-three (17 correlational, 16 experimental) studies that met the inclusion criteria were included. With the correlational studies 16 out of the 17 studies found significant associations between norms and food intake, while all 16 experimental studies found effects of norm manipulations on food intake, and some evidence of behavioral spillover effects of norms. Also, four moderators were identified from the literature synthesis that stipulate for whom and when peer social norms are related to food intake: identification with the norm referent group and eating-related habit strength were seen to moderate the effects of social norms on food consumption; forceful injunctive norms did not indicate correlations with food intake; and the influence of norms seemed restricted to types of foods typically consumed in the presence of peers. These findings have important implications for research and also potentially for the development of social norm-based interventions to improve young people’s food intake. [NPID: psychosocial, peer social norms, habits, young people]

Jeong & Jang (2020) inspected the data from the 2013-2017 Korean National Health and Nutrition Examination Survey (KNHANES) involving 23,494 adult participants in their study to examine the relationship between meal companions and obesity among a South Korean sample population. Participants were first divided into three categories: dinner with family, dinner with others, and dinner alone. A multinomial logistic regression analysis revealed people who ate dinner with others or alone had a higher obesity risk compared to those that had family dinners, and this was the case regardless of their breakfast companion. Moreover, those adults who had daily meals outside of their homes had a greater risk of becoming obese than those who ate dinners with others or with family. It was also discovered regular drinking increases obesity risk, as seen in those who engaged in weekly heavy drinking compared to those who did not drink. This investigation highlighted the benefit of family dinners over having dinner alone or with others, which could motivate dieters to have more frequent family dinners. [NPID: psychosocial, Korea, obesity, South Korea, family dinners]

This is a systematic review published in 2018 examining the research on the influence of cooking interventions on psychosocial outcomes. Eleven studies met the inclusion criteria and were reviewed to find that inpatient and community-based cooking interventions yielded positive influences on socialisation, self-esteem, quality of life, and affect. But generally, the quality of the research was weak due to non-randomisation, unvalidated research tools and small sample sizes. Although this review suggests that cooking interventions may positively influence psychosocial outcomes, this evidence is preliminary and requires back-up from additional qualitative and rigorous quantitative research to identify the mechanisms by which cooking interventions may improve psychosocial outcomes. [NPID: psychosocial, cooking interventions, socialization, self-esteem, quality of life, affect]

This 2019 online article outlines findings from research studies on how obesity, psychosocial stress, and both have an impact on the physiology of different organs. Dugaucquier and Segers (2019) express their interest on clearing up how psychosocial stress affects cardiac and hippocampal function in obese subjects. The writers present an option in the pharmacological administration of brain-derived neurotrophic factor (BDNF) which may compensate for the negative effects of obesity and psychosocial stress on cardiac and neural dysfunction. [NPID: psychosocial, obesity, psychosocial stress, organ health, cardiac function, hippocampal function, brain-derived neurotrophic factor, BDNF, neural function]

Robinson et. al (2014) assessed the weight of evidence that experimentally manipulated information about eating habits has an impact on food choice and intake, and also reviewed studies on whether sharing with people what others’ eating habits look like has an influence on the same matter (food-related decision making). Using a narrative synthesis approach searching on 3 electronic databases (PsycINFO, MEDLINE, and the Social Sciences Citation Index) a total of fifteen experimental studies were selected to be reviewed. Meta-analyses were used to synthesise the effect that informational eating norms have on quantity of food consumed. There was evidence that both high and low intake norms (both p-values <=0.005) exerted moderate influence on consumption quantity. Norms were consistently found to play an influential role in food choices, while norm information about others’ low-energy and high-energy eating habits was significantly linked to an increase in adoption of similar food choices. This study clarifies that eating norms can be an important tool to promote healthy diet choices since they can have such an influence on the choice and amount of food eaten. [NPID: eating habits, psychosocial, intake, norms, food choice, decision making].