Research to date has reported that students transitioning to university experience a variety of lifestyle changes including: increased social eating activities, more alcohol drinking occasions, altered dietary behaviours, and a decline in physical activity (Anderson et al., 2003; Butler et al., 2004; Crombie et al., 2009; Vella-Zarb & Elgar, 2009). Students report low consumption of foods, such as fruit and vegetables, and high consumption of energy dense snack foods (AL-Otaibi, 2014; Alsunni & Badar, 2015;
Dodd et al., 2010; Keller et al., 2008; Khalid et al., 2011; King et al., 2007; Musaiger et al., 2011). Therefore, attempts have been made to improve the diet of young people (Laska et al., 2012; Nelson et al., 2008). There is evidence that behaviour change techniques such as motivational strategies, behavioural counselling, feedback and self-monitoring may be effective in encouraging healthy eating and physical activity (Dombrowski et al., 2010; Michie et al., 2009; Michie et al., 2011). Nevertheless, the levels of healthy food intake are still below the recommended guidelines from the National Health Service (Health Survey for England, 2013). Adults aged between 16 and 24 consume the lowest level of portions of fruit and vegetables and are least likely to consume the recommended 5 portions of fruit and vegetables per day, compared to
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other age groups (Health Survey for England, 2013). Therefore, alternative strategies are needed to improve the diet of young people.
Evidence is accumulating to suggest that behavioural based interventions may be more beneficial if they target social networks. For example, obesity has been reported to spread within social networks, possibly via the influence of social norms on eating behaviour (Christakis & Fowler, 2007). Social norms are defined as the rules and standards that are accepted by a certain group and can be used to guide behaviour.
Several theories have emphasised the influence of social norms on behaviour including the Focus Theory of Normative Conduct (Cialdini et al., 1990; Perkins & Berkowitz, 1986), the Theory of Planned Behaviour (Ajzen, 1985; Ajzen, 1991), Social Cognition Theory (Bandura, 2001) and the Theory of Normative Social Behaviour (Rimal & Real, 2005). Social norms are categorized into two main types: descriptive norms, which refer to beliefs about what other people do, and injunctive norms, which refer to beliefs about what is approved by others (Cialdini et al., 1990).
The impact of social norms on attitudes and behaviours has been explored in a variety of studies including cancer screening intentions (Smith-McLallen & Fishbein, 2008), alcohol consumption (Perkins & Berkowitz, 1986; Perkins, 2002), the use of tobacco (Ali & Dwyer, 2009; Etcheverry & Agnew, 2008; Mead et al., 2014) and promoting household energy conservation (Schultz et al., 2007). Evidence suggests that drinking behaviour is related to students’ personal attitudes toward drinking and perceptions
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about the prevalence of drinking (Chawla et al., 2007). The more consistency there is between individual attitudes and the group norm, the more likely students are to engage in drinking behaviour (Perkins & Berkowitz, 1986).
In recent years, much progress has also been made in exploring the influence of social information on dietary behaviours. There is robust evidence that people tend to follow others’ dietary choice as a guide to what they should eat (e.g. Burger et al., 2010;
Hermans et al., 2012; Lally et al., 2011; McFerran et al., 2010; Pelletier et al., 2014;
Perkin et al., 2010; Robinson et al., 2013; Robinson et al., 2014; Stok et al., 2014;
Vartanian et al., 2013). For instance, there is evidence that peer social norms predict both intended and actual fruit intakes (Stok et al., 2012). It is assumed that perceived eating norms predict the frequency of food consumption such that individuals who perceive that others frequently eat a certain type of food consume the same type of food more frequently than those who do not perceive such an intake. For instance, when people believed that other participants selected predominately unhealthy snack foods, their subsequent unhealthy snack food consumption increased significantly (Burger et al., 2010). In addition, perceived descriptive peer norms have been shown to affect people’s food intake and choice in lab studies. For instance, exposing students to a descriptive social norm suggesting that most students consume less junk food than they might realize, led to a significant decrease in high calorie snack food consumption (Robinson et al., 2013). Conversely, exposing students to a descriptive social norm message suggesting that most other students consume plenty of fruit and vegetables
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resulted in a significant increase of fruit and vegetable intake (Robinson et al., 2014).
The effect of descriptive social norms has been found to be moderated by participants’
habitual food consumption (Robinson et al., 2014). Low usual consumers but not high usual consumers of fruit and vegetables increased their intake after exposure to the norm that most other students consume healthy food regularly (Robinson et al., 2014), although such a habitual intake effect was not consistently observed in some other studies (Robinson et al., 2013; Thomas et al., 2016). It was also demonstrated that descriptive social norms are effective to enhance broccoli intake among low habitual consumers even 24 hours after exposure to the norm (Thomas et al., 2016). Low consumers are more motivated to change their eating behaviour to come in line with the norm, while high consumers may already be adhering to the norm presented.
Previous research has suggested that descriptive social norms may be more effective in promoting healthier eating than are injunctive norms (Robinson et al., 2014; Stok et al., 2014). It may be the case that descriptive norms involve low levels of cognitive activity and thus are more influential than injunctive norms, which involve more complicated cognitive processes (Jacobson et al., 2011; Mollen et al., 2013). Alternatively, individuals may demonstrate psychological reactance to injunctive norms, meaning that they do not comply when they are told what they should or should not do (Brehm, 1966;
Hong et al., 1944). Further investigation of both types of norm is required to understand better their influence on eating behaviour.
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A broader question concerns the mechanism by which exposure to social norms affects behaviour. One possibility is that exposure to social norms corrects the misperceptions of other people’s eating behaviour (Anderson, et al., 2009; Moreira et al., 2009). For instance, there is evidence that misperceived unhealthy sugar-sweetened beverage consumption contributes to an excess calorie intake (Perkins et al., 2010). The same might be true of energy dense foods; we might misperceive that others consume these foods frequently and this perception influences our own consumption. Misperceptions may be especially problematic among college students, as their social distance is much closer than other social groups (Bourgeois & Bowen, 2001).
To date, studies have primarily used cross-sectional designs and observed a positive association between perceived peer eating norms and consumption of fruits, vegetables, snack and fast foods, and sugar-sweetened beverages (Ball et al., 2010; Pelletier et al., 2014; Robinson et al., 2016). One recent longitudinal study reported that among university students, believing that one's peers frequently consumed cakes/pastries was associated with an increased frequency of consumption of these foods over time (Jones
& Robinson, 2017). We also found no association for other food/drink items. However, whether eating norm perceptions (or misperceptions) are causally related to a wider variety of dietary intake, and whether changes in norm perception are related to changes in self-reported intake has yet to be fully investigated.
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Therefore, the aim of the present study was to conduct a longitudinal investigation of the relationship between changes in perceived social norms and self-reported food intake among university students over 12 months of an academic year. It was hypothesized that there would be a misperception of food consumption among college students, whereby students would hold more negative perceptions of their peers’
consumption compared to their own (i.e. greater consumption of junk food and lower consumption of fruit and vegetables by their peers). It was further hypothesized that changes in norm perception and baseline norm perception would predict students’ self-reported intake over 12 months. We assessed both injunctive and descriptive norms.
Finally, we hypothesised that any relationships between norm perceptions and reported intake might be moderated by levels of habitual intake. That is, the increase in norm perception may lead to an increase in self-reported food intake, but this might be more likely among people who are low habitual consumers.