Sawka et al (2015) produces this systematic review examining the impact of friendship networks (including factors such as friends’ dietary behavior, popularity) on an individual’s dietary behavior among children and adolescents. To be eligible studies had to include participants aged between 6 and 18, to measure the subject’s friendship network as well as habitual dietary behavior for both the participant and their friend(s). From 9041 articles retrieved from 6 online scientific databases, a total of seven studies matched the criteria and were included in this review. A connection was found between an individual’s unhealthy food consumption with friends’ unhealthy dietary intake, especially stronger for boys compared with girls. Furthermore an individual’s total energy intake was correlated to that of their best friends’. Even an individual’s unhealthy diet consumption tended to become similar to friends’ poor food choice over time. Similarities between friends’ healthy food consumption and intake of breakfast were inconclusive. But this review highlights the influence of friends on unhealthy diet decisions among adolescents and provides us with a greater insight into adolescent dietary behavior. If healthier diet behaviors could be instilled into these adolescent friendship groups, unhealthy damaging eating habits could be possibly cut down, which could improve weight status among the youth population.

This novel 2020 study examined changes in snacking behavior and four types of social norms (parental and peer descriptive and injunctive norms) that encouraged adolescents to consume more fruits and vegetables, as well as looking at whether snacking behavior influenced norm perceptions by testing the directionality of these associations. The 819 participants of this study (M [SD] age = 11.19 [1.36]; 46.1% boys) reported how often they ate snacks, while perceived parental and peer descriptive and injunctive norms were also assessed. Model comparisons testing the descriptive and injunctive norms in separate models and in an additional combined model revealed evidence for bi-directional associations between norms and snacking behavior. Perceived injunctive parental norms were positively associated with healthy snack food intake and negatively associated with unhealthy snack intake (forward direction). Negative association were found between injunctive peer norms and healthy food consumption, in addition to greater unhealthy snack intake being linked with perception of descriptive and injunctive parental norms 1 year later (reversed direction). Descriptive peer and parent norms were not found to have an effect on subsequent snacking behaviors, and peer norms were not found to be more closely associated with changes in snacking behaviors compared to parental norms. Bevelander and colleagues (2020) conclude that parents simply acting as a healthy role model does not have a positive effect on healthy snack behavior and better results are achieved by expecting the children to snack healthily. This current study encourages future studies to consider the bi-directional relations between eating behaviors and normative perceptions, as well as the possible interaction between descriptive and injunctive norms.

This current study surveyed 757 sets of adolescents and parents to test the amount of influence parents have on their adolescents compared to the power their peers have, with regard to fruit and vegetable consumption in this case. It was found that parents still hold more influence on the adolescents’ fruit and vegetable intake, with the importance of descriptive norms (what they do) greater than injunctive norms (what they say). The researchers help raise awareness of how critical parents still are even at the adolescent stage, and provide a better understanding of what influences adolescent healthy eating and how parents and peers can have a significant effect. Pederson et al (2015) implicate that: healthy eating interventions should aim at strengthening self-efficacy and positive outcome expectations among adolescents; the family context should be included when implementing healthy eating interventions; and parents should be made more aware of their influence on their children’s healthy eating.

Van den Broek et.al (2020) provide us with a rare study simultaneously investigating associations of mothers’ and best friends’ dietary intake with an adolescent intake of healthy and unhealthy foods, obtained from and outside the home, and the moderating role of the adolescents’ exposure to their food intake. 667 adolescents took part in the experiment (53% female, Mage = 12.9) along with 396 mothers and 378 best friends, who all completed food frequency questionnaires to determine dietary consumptions. The adolescents were allowed to discuss their food and drink intake with the researchers in the presence of their best friends, while the mothers reported separately on their diet either in the presence or in the absence of their child. The findings include positive correlations between the mothers’ diet (and not the best friends’) with the adolescents’ consumption of healthy and unhealthy foods. While exposure to the best friends’ unhealthy food behaviors moderated adolescent-friend similarities in unhealthy food consumption, similarities in healthy food intake was found to be enhanced by exposure to the mother’s healthy eating. The current study calls for more research into the mechanism in which these similarities arise, and further investigation of these associations over time and in later development periods.

Although evidence of mother-child similarities in dietary behavior has been identified so far mostly using cross-sectional design, this study delivers a longitudinal look into the association - firstly examining whether maternal snacking can predict changes in the adolescents’ snacking over time and secondly, inspecting the relevance of the adolescents’ television viewing time to the strength of the mother-child snacking association. The hypothesis was that television viewing may increase the urge to snack what the mother ate later on, through food advertisement exposure and mindless eating for example. 2051 adolescents (Mage baseline = 13.81; 51.5% boys) were asked to report on their snacking and television viewing three times, with intervals of one year, and in addition the 1080 mothers reported on their snacking at baseline. The results indicated that maternal snacking predicted the adolescents’ snacking over time, with this observed effect more pronounced among the adolescents who watch a lot of television. The importance of mothers in forming adolescents’ prospective snacking is highlighted by this study, as well as the relevance of assessing home environmental factors that may influence maternal effects on their children’s snacking.

Since social resources such as trust, reciprocity, social participation, integrity and coherence are supposed to assist the common people to achieve their goals, in life and in health, this current study investigate the relationship between social capital within its different contexts and adherence to the Mediterranean Diet (MD) among Lithuanian adolescents. 1863 students (906 males: 957 females) were assessed regarding their family support, neighbourhood trust, social control, vertical trust, horizontal trust and reciprocity at school. Their adherence to the MD was also determined by the KIDMEX index questionnaire (Mediterranean Diet Quality Index in children and adolescents). Covariates such as gender, physical activity, parental education, and body mass index were also included in the analysis. There was evidence that only 14% of Lithuanian adolescents followed a MD, with linear regression analysis showing correlation shown between family support and trust in school teachers with more frequent breakfast intake and higher MD adherence rates, especially with regards to consumption of fruits, vegetables, cereals, fish and the use of olive oil as main source of fat. These findings could encourage nutrition education programs to consider and integrate improving support and trust among family and schoolteachers.

In this study thirty three studies were selected and reviewed - of which 17 were correlational and 16 were experimental design - to examine the role that social norms play in shaping young people’s diet consumption, with particular attention on for whom and when peer social norms become relevant in how much a young person eats. Significant associations between norms and food intake were found in all but one correlational study, while all experimental studies discovered effects of norm manipulations on diet and some data showed behavioral spillage effects of norms. The literature synthesis implemented by the current study pointed out: identification with the norm referent group and eating-related habit strength moderate the effects of social norms on food consumption; forceful injunctive norms were not related to dietary intake; and the influence of norms seemed restricted to typical foods eaten in the presence of peers. These moderators discussed are relevant to psychological theory, and not only that, these findings have important implications for research and could be potentially applicable in the development of social norm-based interventions aimed at enhancing the dietary consumption of our young population.

Using the 8-country IDEFICS study (7675 participants aged 2-9 years old), Arvidsson et al. (2017) set out to determine the chronology of the association between children’s adherence to healthy dietary guidelines with health, while focusing particularly on the impact of weight on this relationship. The children were examined in 2007/2008 and then again 2 years later, using self-esteem and parent relations questions from the KINDL® and emotional and peer problems from the Strengths and Difficulties Questionnaire to measure mental health. A 43-item food frequency questionnaire was also completed to gather dietary information and calculate the young subjects’ Healthy Dietary Adherence Score (HDAS). A higher adherence (HDAS) at baseline was associated with better outcomes 2 years later, such as improved self-esteem (OR=1.2), and fewer peer and emotional issues (ORs 1.2 and 1.3). Similar associations of higher HDAS at baseline/enhanced health were found in both normal-weight and overweight children, revealed by the weight-stratified analysis. Moreover, increase in self-esteem was related with higher HDAS 2 years later (OR=1.1), indicating a bidirectional relationship between diet quality and self-esteem. In addition, these results showed that children more adherent to healthy dietary guidelines at baseline were more likely to have fewer emotional and peer problems at the 2-year follow-up, regardless of weight status.

Since perceived peer eating norms have been shown to influence dietary behaviour, this 2016 study investigated whether certain personality traits are linked with leading eating habits similar to perceived peer eating habits. One thousand and fifty-six young adults were asked about their perceptions on the level of sugar-sweetened soda (SSS) and sweet pastries (SP) consumed by their peers. The participants also reported their own intakes of these foods and drinks. Perceived peer eating norms for both sugar-sweetened soda and sweet pastries predicted frequency of consumption. Having a belief that peers were frequently consuming SSS and SP was associated with elevated personal consumption of both. Those with low self-control, compared with high self-control, were more likely to adhere to peer norms for SP, but not for SSS. But trait social acceptance needs did not significantly moderate similarity between peer norms and personal consumption for either SSS or SP. Robinson et al. (2016) conclude that the degree to which young adults adhere to descriptive peer dietary norms may depend on their self-control, meaning that those with low self-control may be less able to block out social influence of peer norms on dietary behavior.

Sharps & Robinson (2017) conducted two studies to demonstrate again that the eating behaviours of others (perceived eating norms) can influence children's vegetable consumption. The first study tested whether the kids follow these perceived eating norms as they want to maintain personal feelings of social acceptance, while the second study was designed to check whether perceived eating norms influence eating behaviour because eating norms provide information which can remove uncertainty about how to behave. In both studies, the children were exposed to vegetable intake data of their peers. The kids were affected by a perceived eating norm regardless of whether they felt sure or unsure that other children accepted them (in both studies). Study 2 indicated the larger influence of a perceived eating norm if they were eating in a novel context in which they were uncertain how to behave, relative to a familiar eating context that had already been encountered. In conclusion, perceived eating norms may modify children’s eating behavior by removing uncertainty about how to behave.

Tashiro et al. (2020) conducted questionnaire surveys in disaster-affected areas following the 2011 Great East Japan Earthquake and Tsunami, to assess the relationship between the motivation to participate in cooking classes and the classes’ impact on the individuals. The survey examined the following effects of class participation: increase in new acquaintances and friends; more excursion opportunities; potential for gaining motivation; and a new sense of life purpose. The surveyors obtained 257 valid responses from 15 cooking venues. Several combinations of motivation and eating patterns were associated with the respondents’ perceived participation effects. For example, people who reported to eat alone and were motivated to enhance their nutritional intake were more likely to make new acquaintances and friends. Eating alone and being motivated for increasing personal cooking skills was linked with gaining additional excursion opportunities. Conversely, those who ate alone and whose drives were to improve their nutritional consumption were less likely to increase their excursion opportunities. The results indicate the success of the cooking class, as participation provided the residents with nutritional health support and social benefits.

While studies have demonstrated that individual perceptions of their peers’ eating and drinking habits are linked with their own dietary behaviors (types, frequency, and quantity of food and drinks), Jones & Robinson (2017) highlight the limited data available on this correlation between perceived descriptive peer norms and future eating or drinking behavior. This present study examined 340 university students twice on their perceived descriptive peer norms and how frequently they ate cakes/pastries, sugar-containing beverages, and alcoholic drinks. Perceived descriptive peer norms were found to predict the intake of pastries/cakes at follow-up when controlling for changes in these perceptions over time. Although the degree of effect was small, students who believed their peers frequently ate cakes or pastries were more likely to consume that food more frequently themselves over time. However, there was no association between perceived descriptive peer norms and changes in consumption frequency of sugar-containing drinks or alcohol over time. These results indicate that the perception of peers’ frequency in specific food and drink consumption barely influenced future personal eating and drinking behavior.

The purpose of this 2020 study was to analyze the key underlying mechanisms by which preadolescents’ healthy eating behaviors are influenced by peer-related social factors. Ragelienė & Grønhøj recruited 278 Lithuanian preadolescents from a public school, and administered them with questionnaires on sociodemographics, peer-related social norms of healthy eating, food intake, vegetable preference, need for peer approval, and feeling of belonging. The results indicated that social self-efficacy predicts feeling of belonging to the peer group and need for peer approval, while feeling of belonging and need for peer approval predict actual intake of vegetables. However, neither feeling of belonging nor need for peer approval predicted descriptive norms of healthy eating. Also, descriptive norms were not related to consumption of vegetables, which surprised the researchers. But vegetable preference predicted actual intake of vegetables. Peers’ social norms of healthy eating did not predict vegetable preference either. These findings emphasize the importance of social relations when encouraging preadolescents to eat healthy foods.