Diet and Psychosocial

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.

8523 Korean adults were assessed by Chae et. al (2018) with the hope of discovering an association between eating alone and diet quality in Koreans who eat alone and of analysing how socioeconomic factors can influence their diet quality. Using the Korean National Health and Nutrition Examination Survey (KNHANES) VI 2013-2015 data, diet quality was determined by mean adequacy ratio (MAR) and nutrient adequacy ratio (NAR). It was found that those who eat alone have lower diet quality compared to those who eat together in both males and females. Among the lone eaters, MAR was negatively influenced by living arrangement, education level, income levels, and various occupation classes. The finding that people who eat alone are lacking in nutritional intake could lead to serious health problems, which is why the authors support the development of strategies by the policy makers to enhance diet quality in order to prevent potential risk factors.

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.

This 2019 study examined the synergistic and relative association between a number of food environmental and psychological factors with the dietary behaviors of 921 women with young children. The female participants from Hampshire were asked about their demographic characteristics, psychological resources, dietary behaviors and perceptions of healthy food access and affordability. Three local food environment factors were objectively assessed: 1) spatial access to food outlets using activity spaces; 2) healthfulness of the supermarket where women did their main food shop (based on nine in-store factors including price, placement and promotion on seven healthy and five less healthy foods); 3) nutrition environment of children's centres visited frequently by the women, assessed via staff-administered questionnaire. For the results, complete data were available for 753 women. One of the findings was that the environment of the women’s supermarket was indirectly related to their dietary behaviors through psychological resources and perceived food affordability. The overall model fit was good, and the three food environmental factors were not directly associated with dietary behavior. An association was observed between shopping at supermarkets classified as having a healthier in-store environment with greater psychological resources, with links to healthy eating and fewer food affordability concerns. These results suggest that combining high-agency interventions that target individual psychological resources and low-agency supermarket environment interventions can lead to greater improvements in dietary behaviors than either intervention alone.

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.

This 2018 study extracted data from the Korea National Health and Nutrition Examination Survey (KNHANES) for 2013-2015 (yielding 8988 adults aged 18-64) in order to examine the relationship between patterns of eating alone and the risk of metabolic syndrome (MetS) in Korean adults. Patterns of eating alone were categorized into eight groups based on the total frequency of eating alone on a daily basis in the past one year: (1) three times for breakfast, lunch, and dinner; (2) twice for breakfast and dinner; (3) twice for lunch and dinner; (4) twice for breakfast and lunch; (5) once for breakfast only; (6) once for lunch only; (7) once for dinner only; and (8) never eating alone. The presence of MetS was defined by the National Cholesterol Education Program Adult Treatment Panel (NCEP ATP III) and International Diabetes Federation (IDF). After controlling for age, income, occupation, number of family members, generation types, marital status, smoking status, and physical activity, the study found the prevalence of MetS was the highest in men and women aged 40-64 who had breakfast, lunch, and dinner alone (50.1% and 36.8%, respectively). In addition, men who had dinner alone or lunch and dinner alone had significantly higher risks of developing MetS compared to those who eat with others, with adjusted odds ratios (AORs) of 1.51 and 1.54 respectively. However women who had breakfast alone appeared to have a significantly lower risk of MetS compared to those who ate with others. In conclusion, patterns of eating alone are differentially associated with the risk of MetS in a representative sample of Korean adults. Lastly, Kim et. al (2018) believe more studies are warranted to identify the different eating alone patterns in relation to various health outcomes in Korean adult populations.

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.

Since family dinners can be where the whole family gets together and can potentially have a positive effect on depression severity, this 2016 study investigated the association between dinner companion and depression, as well as the differences in this link by gender, living arrangement and household composition. 4181 participants from the Korea National Health and Nutrition Examination Survey 2014 were included in this study and were divided into 3 groups according to their dinner companions: dinner with family, dinner alone, and dinner with others. Results showed those who ate dinner alone (OR = 1.53) were more likely to develop depression compared to those who had family dinners, and that men who live with others and men who live in a second generation household who ate dinner alone had more chance of suffering from depression. It was concluded in this study that family dinner times may help to alleviate depressive moods.

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.

Collins et. al (2019) set up two observational studies to test the hypothesis that descriptive social-norm messages are associated with increased vegetable consumption, which there is some evidence of in laboratory-based studies. A vegetable-related social norm such as "Did you know that most students here choose to eat vegetables with their meal?") and a health message for example "Did you know that students who choose to eat vegetables have a lower risk of heart disease?") were displayed in two different student canteens, and purchases were reviewed at baseline, when the posters were displayed (intervention), and immediate post-intervention (when the posters had been removed). The first study analysed the purchase of meals containing a portion of vegetable while study 2 observed sales of vegetable side portions. Study 1 discovered that relative to baseline, the social-norms intervention was associated with an increase in purchases of vegetables (from 63% to 68% of meals; OR = 1.24, CI = 1.03-1.49), which was sustained post-intervention (67% of meals; OR = 0.96, CI = 0.80-1.15). The health message did not appear to have an effect on sales of vegetable-containing foods in the first cohort, with 75% of meals seen at baseline and 74% during the intervention (OR = 0.98). Whereas with the second study, the health message led to a rise in ratio of vegetable purchases from 43.8% at baseline to 52.8% during the intervention, an effect that was sustained after the intervention (48.1%, OR = 0.59). Other findings from study 2 included an increase in percentage of vegetable purchases from 22.9% at baseline to 32.5% when the social norm intervention was in play, but this effect was not maintained post-intervention (22.1%). The author claims these results support further testing of the effectiveness of such messages in encouraging healthier eating and indicate the need for larger-scale testing at multiple sites using a randomised-controlled design.

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.

Patel & Schlundt (2001) investigated the relationship of moods and social context with energy and nutrient intakes to find out whether these variables interact or function independently. The study used a sample population of 78 predominantly white, obese women (mean age 36.7, mean BMI 32.1) participating in weight-loss studies. The subjects recorded food consumption, moods, and people present during these meals within food diaries over the course of 2 weeks. Results showed meals eaten in a positive or negative mood were significantly larger than those eaten in a neutral mood. In addition, meals with company were significantly larger in size than meals eaten alone. Moods and social context had an additive effect resulting in greater risk of overeating, while it was revealed by macro nutrient analysis that the main influence was from social context. Percentage of calories from fat and protein were greater, whereas the percentage of carbohydrate was less in social context meals compared to meals eaten alone. Patel and Schlundt (2001) concluded that educating individuals to cope more effectively with social situations and moods may improve the efficacy of weight loss and maintenance programs.

The effects of liking norms and descriptive norms on vegetable consumption: A randomized experiment

Perceived social norms and eating behaviour: An evaluation of studies and future directions

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.

What everyone else is eating: a systematic review and meta-analysis of the effect of informational eating norms on eating behavior

Social norms shift behavioral and neural responses to foods

Social modeling of eating: a review of when and why social influence affects food intake and choice

Liking food less: The impact of social influence on food liking evaluations in female students

Impact of nutrition on social decision making