Snacking behaviours of adolescents and their association with skipping meals

The rapid increase over the past three decades in the prevalence of childhood obesity in developed countries across the world [1] has led to increased concern about the diets of adolescents and children [2, 3]. Although increased levels of sedentary behaviour are likely to be associated with this increase in obesity [4], changes in food consumption patterns are also likely to play an important role. Several dietary behaviours have been linked with adult and childhood obesity, including increased number of meals eaten outside the home [5], larger portion sizes of meals at restaurants and fast-food takeaways [6], and increased consumption of soft drinks [7, 8]. The increasing prevalence of snacking has also recently been suggested as a potentially important influence on energy regulation in adolescents [9] and adults [10, 11].

The prevalence of snacking (defined as the consumption of foods and drinks between meals including milk drinks, regular soft drinks, sports drinks and energy drinks) among adolescents and children varies widely across the world. For example, 87–88% of American adolescents (aged 12–18 years) consume at least one snack per day [12–14], with snacks contributing approximately 25% of their daily energy intake. In European countries, snacking is also highly prevalent, with Scottish adolescents (aged 15 years) consuming on average 2.8 snacks per day [15] and Portuguese youth (aged 5–15 years) consuming 1.5 snacks per day [16]. In Asian countries, snacking rates among youth (aged 2–19 years) are more variable. For example, in the Philippines, Russia and China, 86%, 71% and 10% of youth consume at least one snack on a daily basis, with snacks providing 18%,16% and 1% of their total daily energy, respectively [17].

Snacking is also commonly associated with undesirable health outcomes and dietary patterns. Since children and adolescents select snacks based on taste over nutrition, they more often choose salty, crunchy foods as snacks over healthier alternatives [12]. Consequently, snacking is commonly regarded as a contributing factor in the development of childhood overweight and obesity, although studies that have examined the association between snacking and body mass index have yielded mixed results [3, 9, 11, 18]. Although evidence is limited, snacking may also be associated with less frequent consumption of meals, which may be detrimental to health since regular meal patterns are associated with greater dietary diversity [19], healthier food choices [20] and better nutrient intakes [21, 22].

The literature exploring associations between snacking behaviour and demographic characteristics in children and adolescents is relatively scarce and contradictory. For example, the few studies that have examined the association between gender and snacking have yielded mixed results, with more frequent snacking reported among boys than girls [13, 23] and vice versa [14], while some studies have failed to report gender differences at all [12, 24]. In contrast, the few studies that have examined whether snacking varies with age, region of residence and socioeconomic status have yielded more consistent results. Snacking among children, adolescents and young adults occurs more often in younger than older subjects [12, 13, 16], more often in urban than rural residents [17], and more often in subjects from families with higher incomes [13, 24, 25] and education levels [13].

Surprisingly little is known about the context of snacking in adolescents, or how snacking may influence other dietary habits, such as meal skipping. While previous research shows that snacking among children and adolescents occurs most often in the afternoon [12, 15, 26] and at home [12, 17], information about the specific contexts in which adolescents snack (e.g. while doing homework or working, while watching television) is lacking. Similarly, while meal skipping has been shown to be associated with a higher snacking frequency among both adolescents [22] and adults [11, 27], to our knowledge no study has yet explored whether snacking is associated with a higher frequency of meal skipping.

The aim of the present study is to examine the contexts in which adolescents snack and to determine whether snacking contexts are associated with gender, year level, or region of residence. In addition, this study aims to examine whether snacking is associated with a higher frequency of meal skipping, and more specifically, which snacking contexts predict meal skipping.

This study explored the contexts in which adolescents snack and whether these contexts were associated with demographic characteristics of adolescents and with skipping meals. Adolescents most frequently snacked after school, while watching TV, and while hanging out with friends. They snacked less frequently while doing homework or working, on the run and on the way to or from school, but were least likely to snack all day long and in the middle of the night. While these snacking contexts were variously associated with gender, year level and region of residence, meal skipping was only associated with gender and year level. Adolescents who reported more frequent snacking on the run, on the way to or from school, all day long, or in the middle of the night were more likely to skip meals.

The finding that adolescents snacked most frequently after school is consistent with previous research showing that children and adolescents snack most often in the afternoon [12, 15, 26]. The reasons for this are likely to be physiological, as well as related to school policy in Australia. Given that adolescents have high energy demands due to rapid growth and development [30], and given the typical Australian lunch is usually a light, uncooked meal (e.g. sandwich) brought from home, students are likely to be hungry after school. In addition, snacking is not usually permitted in class time and consequently the first opportunity students have to snack (following the lunch break) is after school. Adolescents also snacked frequently while watching TV, which is not surprising given that television viewing has previously been shown to be positively associated with snacking [31–33].

Snacking frequencies in different contexts varied according to the demographic characteristics of adolescents. Year level was positively associated with the frequency of snacking in two contexts; adolescents in year 9 were more likely than their younger peers in year 7 to report that they often snacked while hanging out with friends and all day long. These findings contrast with previous studies that have found a decline in snacking as children become older [12, 13, 16], however these studies covered a wider range of ages and compared overall snacking frequencies.

Several snacking contexts were associated with gender but the direction of these associations was mixed. Boys were more likely than girls to report that every day they snacked on the way to or from school and in the middle of the night, whereas girls were more likely to report that they often snacked on the run, while hanging out with friends and while doing homework or working. The mixed direction of these associations is consistent with previous studies on gender differences in snacking, which also yielded mixed results [12–14, 23, 24]. However, the higher reported frequency of snacking among girls while hanging out with friends and while doing homework or working may reflect the greater time girls spend with their friends [34] and doing homework [33, 35]. That boys were more likely than girls to snack in the middle of the night is consistent with a recent study of the eating patterns of Swedish adolescents, which also found boys eat more throughout the night than girls [36]. This study also reported that more boys than girls eat between 0600 and 1000 hours, which is consistent with our finding that boys were more likely than girls to snack on the way to school.

Several snacking contexts were associated with region of residence. Adolescents from metropolitan regions were more likely than non-metropolitan adolescents to report that they often snacked in the middle of the night, while doing homework or working and while watching TV. A higher frequency of snacking among children and adolescents (aged 2–18 years) from urban areas has also been reported in several other countries, including China, Russia, the US and the Philippines [17]. In our study, however, we also found that adolescents from non-metropolitan areas were more likely than their peers from metropolitan areas to report that they snacked every day after school. Adolescents from non-metropolitan areas may have more opportunity to snack after school since a larger proportion are transported directly home from school via a school bus. In contrast, metropolitan students have greater flexibility regarding their transport options home. This enables them greater opportunities to pursue activities outside the home, which may restrict their access to snacks, but also their snacking behaviour as a result of the activity per se.

Meal skipping was associated with gender and region of residence. Females were more likely than males to skip breakfast and lunch. Similarly, adolescents from metropolitan areas were more likely than their peers from non-metropolitan areas to skip breakfast. Previous studies have also reported a higher frequency of breakfast skipping among female adolescents [37, 38]. In addition, a recent study of meal skipping patterns among fourth grade children from distinct geographical locations in Maryland, USA, found that urban students were more likely to skip breakfast compared with suburban and rural students [39].

This study also assessed the association of snacking in different contexts with the skipping of meals. Adolescents who frequently snacked on the run, on the way to or from school, all day long, or in the middle of the night were more likely to skip meals. In one Australian study, the two major reasons adolescents most commonly reported for skipping breakfast included a lack of time in the morning (52%) and not being hungry (22%) [38]. Snacking on the run and on the way to or from school are behaviours that could be associated with a lack of time and support our finding that snacking in these contexts increased the likelihood of adolescents skipping breakfast, compared with adolescents who did not snack in these contexts. By snacking in the middle of the night adolescents reduce the length of the overnight fasting period, which may diminish their sense of hunger, and thereby increase their likelihood of skipping breakfast. Snacking all day long is also likely to affect hunger at subsequent meals.

Interestingly, the contexts in which adolescents most commonly snacked (i.e. after school, while watching TV, while hanging out with friends, while working or doing homework) were not associated with skipping meals, while those contexts in which adolescents least commonly snacked (i.e. on the run, on the way to or from school, all day long and in the middle of the night) were associated with skipping meals. Snacking all day long and in the middle of the night may be regarded as the most health-compromising of the contexts we considered. Our finding that these contexts were those associated with meal skipping (a mildly disordered eating behaviour) is consistent with several previous cross-sectional studies, which found strong associations between breakfast skipping and various health compromising behaviours (e.g. smoking, alcohol use and sedentary lifestyle) among adults and adolescents [37] and between infrequent meal patterns and disordered eating (e.g. unhealthy weight control behaviours, binge-eating and chronic dieting) among adolescents [40]. These associations, however, should be treated cautiously since only 6% and 11% of adolescents were high snackers in the middle of the night and all day long, respectively.

Strengths of this study include the large and diverse nature of our study population. To our knowledge, this is the largest survey on snacking behaviour of adolescents in Australia. A limitation of our study was its cross-sectional nature, which limits our ability to discuss directionality and causality. We cannot assume that snacking in certain contexts (e.g. in the middle of the night, on the way to or from school) precedes meal skipping. It is equally probable that adolescents who skip meals are more likely to snack in these various contexts, compared with adolescents who do not skip meals. Also, since we did not ask students to indicate what foods or drinks they consumed as snacks, we are unable to determine if the nutritional quality of the snacks varied according to snacking context.

The findings point to a need for further research studying associations between snacking contexts and meal skipping. Future research should aim to employ longitudinal or experimental designs to clarify directionality and provide additional insight into possible causal mechanisms. Future research should also examine whether adolescents consume different types of snacks in different snacking contexts. For example, are adolescents more likely to snack on chips and chocolate (energy dense foods) while watching TV, fruit while doing homework or working, and milk in the middle of the night? Furthermore, does the healthfulness (or energy content) of the snack predict the likelihood of skipping meals. For example, does the consumption of 'unhealthy' or energy dense snacks increase the likelihood of skipping meals? Additionally, is body mass index associated with snacking in different contexts? For example, are overweight or obese adolescents more likely to snack in the middle of the night or all day long, compared with adolescents in the healthy weight range?

Energy and nutrient requirements are greatly increased in adolescence to accommodate the rapid growth and development that occurs during this period [30]. The rising incidence of obesity among adolescents, however, indicates that many youth are consuming more than adequate intakes of energy. Since snacks eaten between meals provide up to a quarter of the daily energy intake in some adolescent populations, limiting snacks may be an effective way for adolescents to reduce their total energy intake. However, given that snacking is such a common dietary behaviour among adolescents, promotion of nutritious snacks (e.g. nuts, fresh fruit and vegetables, bread/toast, milk and pure fruit juice) is crucial. Furthermore, promoting nutritious snacks to those adolescents that skip breakfast may be more useful than encouraging the consumption of breakfast (either at home or school), especially if a lack of time (perceived or otherwise) is the cause of this behaviour. Understanding the contexts in which adolescents snack, and their relationships with meal skipping, may help parents and health promotion officers develop strategies to promote healthy food habits among adolescents.