INTRODUCTION
Since the outbreak of coronavirus disease-2019 (COVID-19) in March 2020 in Korea, the disease has spread rapidly across the country. The South Korean government initially ordered the closures of all schools until May 2020, as a social distancing strategy according to the regional distribution of COVID-19 infections [1]. During the closures, classes moved online, and students’ lifestyles were left up to each family to manage. Although a stepwise reopening of schools in South Korea did not result in a surge in pediatric cases, school closures were shown to have significant noninfectious health outcomes [2]. The school closures due to the COVID-19 pandemic have led to changes in lifestyle habits that may hinder children’s healthy development [3]. Research has reported increased sedentary behavior, decreased peer interactions, and increased dysfunctional eating behaviors (or nutritional status and eating habits). One study suggested that lifestyle changes during the COVID-19 pandemic were associated with obesity [4], while another recent study reported an association between child obesity and the number of days after school closure [5]. Particularly, recent studies conducted during the pandemic have suggested that the social isolation itself could be considered a risk factor for consumption of poor-quality foods, such as fast food [6]. Nutritious diets significantly impact overall health, especially during such a period when the immune system is under increased pressure to fight off infection [7]. Several studies also highlight the importance of a balanced diet for mental health. Excessive consumption of fast food is a risk factor for mental illness as it is associated with increased inflammation within specific brain regions [8]. Adolescence is a period of rapid physiological and behavioral changes, and it lays the foundation for adult health. Thus, it is important to pay attention to dietary profiles, especially those of adolescents, who have been highly susceptible to acquiring unhealthy eating habits during the COVID-19 pandemic. Consumption of fast food is reported to be higher in adolescents than in individuals of other age groups [9]. Recent studies show that increased consumption of fast food has been significantly associated with poorer mental health outcomes among adolescents (e.g., anxiety and depression symptoms) during the COVID-19 pandemic [10]. Like this, the increased consumption of fast food among adolescents poses a significant public health concern, due to its adverse effects on health and well-being. However, research investigating the association between fast food consumption and variable associated factors including lifestyle changes during COVID-19 in Korea is lacking. Therefore, the first purpose of this study was to examine the prevalence of and factors related to fast food consumption among adolescents during school closures caused by the COVID-19 outbreak in Korea. In particular, we examined the link between fast food consumption and mental health, as well as lifestyle changes, such as sleep and media use, which are essential for maintaining mental health. Additionally, with no adult caregivers at home due to the unexpected school closures brought on by the COVID-19 outbreak, children may have difficulty establishing and maintaining a healthy daily routine, including preparing their own healthy meals. Thus, we hypothesized that the absence of a monitoring system for healthy daily routines among adolescents, such as a lack of adult supervision, is associated with fast food consumption.
METHODS
Study design and participants
This study analyzed cross-sectional baseline data from a representative sample of adolescent middle and high school students in Gwangju, Korea. Participant information was collected as part of a survey on lifestyle changes and mental health during school closures due to the COVID-19 pandemic. Participant recruitment and data collection were conducted between June and December 2020, when schools had fully reopened. Gwangju is a metropolitan area consisting of five subdivisions. We publicized this study through community mental health and welfare centers in each subdivision, and two community mental health and welfare centers participated in this study. The study participants were limited to adolescents, considering the age at which they can live alone without their parents, even for a short period. At the time of the survey, owing to the COVID-19 pandemic, the start of school had been postponed until after winter and summer vacation depending on the school, and participants had experienced an isolation period of approximately 3 to 4 months. All students received a packet of self-report questionnaires at school when classes recommenced, including a written explanation of the study’s purpose, and they provided informed consent to participate. In total, 1,854 middle and high school students from 10 schools (eight middle schools and two high schools) participated in the survey. The analyses included 1,710 responses (92.2%) after eliminating incomplete responses (Supplementary Figure 1 in the online-only Data Supplement). The Institutional Review Board of Chonnam National University Hospital approved this study (CNUH-2020-157).
Outcomes and measurement
Sociodemographic characteristics included sex, grade level, religion, number of family members, family type (dual-earner family or not), self-rated academic achievement, and self-rated academic stress. The definitions and types of fast food in the questionnaire were created with reference to previous literature [11]. We explained to the students that, in the questionnaire, “fast food” referred to food that can be accessed easily and quickly and requires no preparation, and then provided examples (e.g., instant noodles, hamburgers, pizzas, fried chicken, and white-flour baked goods). To evaluate changes in their fast food consumption, participants were asked to self-report the frequency of their fast food intake per week before school closures and during the months-long school closures due to COVID-19. We classified those reporting increased fast food consumption as the increased fast food consumption group and those not reporting it as the reference group. In addition, six items assessed participants’ lifestyle changes during school closures: “irregular meals (during school closure due to COVID-19, meals patterns have become irregular)”, “irregular sleep time (during school closure due to COVID-19, sleep time have become irregular)”, “reduced physical activity (during school closure due to COVID-19, physical activities have reduced)”, “reduced social interactions (during school closure due to COVID-19, social interactions have reduced)”, “increased internet use (during school closure due to COVID-19, internet using time have increased)”, and “increased online gaming time (during school closure due to COVID-19, online gaming time have increased)”. All items were rated using a 5-point Likert scale ranging from 1 (“not at all”) to 5 (“very much”). The adolescents were also to report the time per day about sleep duration, sedentary behavior including TV watching, internet use, and online gaming, physical activity before and during school closures. Paired samples t-tests which mean of two measurements taken from the same person determined whether changes in participants’ daily behaviors (e.g., sleep, physical activity, sedentary behavior) were statistically significant.
Depression and anxiety symptoms were measured using the Korean versions of the Patient Health Questionnaire-9 (PHQ-9) and the Generalized Anxiety Disorder Scale (GAD-7), respectively. The PHQ-9 items assessed frequency of depression symptoms and were rated on a 4-point Likert scale ranging from 0 (“not at all”) to 3 (“nearly every day”). Higher scores reflect more severe depression [12]. The Korean version of the PHQ-9 is a reliable and valid tool for screening and assessing depressive symptoms in Korean populations [13]. The GAD-7 items assessed frequency of anxiety symptoms and were rated on a 5-point Likert scale ranging from 0 (“not at all”) to 4 (“nearly every day”). Higher scores indicate more severe anxiety [14].
Loneliness was measured using a three-item UCLA Loneliness Scale [15]. We used the Korean version of UCLA Loneliness Scale adapted by Kim. 16 The scale was adapted to assess perceived isolation, with higher scores indicating greater loneliness. We added an item asking about daytime adult supervision during school closures.
Statistical analysis
Between-group comparisons of sociodemographic and clinical characteristics were analyzed using chi-square tests for categorical variables and independent samples t-tests for continuous variables. The associations between fast food consumption and sociodemographic characteristics, including sex and clinical factors, were evaluated using a multivariable logistic regression model controlling for potential confounders. The variables shown to be statistically significant in a univariate analysis were subsequently entered into a multivariable logistic regression analysis to investigate independent associations with fast food consumption as the dependent variable. SPSS 21.0 (IBM Corp., Armonk, NY, USA) was used to perform all statistical tests, which were two-tailed with an alpha level of 0.05.
RESULTS
Participants’ mean age was 15.4±1.7 years. Among the 1,710 students, 936 were boys (54.7%). Participants reported significantly increased fast food consumption during school closures (2.8 meals per week) compared to before the school closures (2.5 meals per week) (not shown table, t=-10.222, p<0.001). Table 1 shows the sociodemographic and clinical characteristics of both groups. Approximately 34.6% of participants (n=592) reported increased fast food consumption during school closures. Girls and middle school students were more likely to be in the increased fast food consumption group. The PHQ-9 and UCLA Loneliness Scale scores were significantly higher in the increased fast food consumption group.
Table 2 presents the time changes in participants’ lifestyle behaviors including sleep duration, physical activity, and sedentary behaviors (watching TV, using the internet, and online gaming) before and during school closures. During school closures, participants reported increased sleep duration, increased sedentary behaviors, and reduced physical activity compared to before the school closures.
The increased fast food consumption group reported more irregular meals and sleep as well as less physical activity and social interactions compared to the control group. They also spent more time using the internet, including playing games online. This group also was more likely to report a lack of daytime adult supervision.
The multivariable logistic regression analysis showed that lifestyle behaviors including irregular meals, irregular sleep duration, reduced physical activity, and increased internet use during school closures were significantly associated with increased fast food consumption. A lack of daytime adult supervision was also associated with increased fast food consumption (Table 3).
DISCUSSION
In this study, adolescents reported significantly increased fast food consumption during school closures brought on by the COVID-19 pandemic. This aligns with a recent study’s finding that habitual ultra-processed food consumption among adolescents was high during the COVID-19 outbreak in all countries [17]. This might be because school closures temporarily halted free school lunches and forced adolescents to spend most of their time indoors, and adolescents may have had more convenient access to fast foods. The number of students who choose their own food, including fast food, is increasing because of factors such as the nuclear family, increase in dual-income couples, and development of the food industry [18,19]. Social isolation during the pandemic may have contributed to worsening food insecurity. However, other studies have found a significant increase in consumption of home-cooked meals and lower intake of fast food among children and adolescents during the pandemic [20]. There is even a report that fast food consumption has dramatically decreased during the lockdown period due to fear of contamination of fast food by coronavirus [21]. This controversial result can be explained due to diversity in food supply chain issues and in family structures of each country during the pandemic. In Korea, restaurants were closed during the pandemic, but the demand for deliveries and convenience food significantly increased. Adolescents’ reliance on food from outside the home could be exacerbated by the absence of their parents, who could prepare nutritious foods. Our result supports this interpretation as a lack of daytime adult supervision was significantly associated with increased fast food consumption. Therefore, nutritional advice to encourage a balanced and healthy diet during school closures should be provided to both students and parents. In addition, to enhance parental involvement, it is necessary to provide healthy ingredients or lunchboxes that students can prepare themselves when their parents are absent and monitor students’ dietary intake.
Additionally, school closures during COVID-19 exacerbated changes in lifestyle habits including sleep, media use, and physical activity, all of which were associated with increased fast food consumption. Particularly, social distancing and online class have made it easier for adolescents to access online content. Consistent with several Korean studies [22,23], this study’s participants reported increased sedentary behaviors such as watching TV, internet use, and online gaming during the pandemic. Recent studies have also shown that prolonged screen time during quarantine was associated with frequent snacking between meals and at night [24]. Our study also revealed a positive association between internet use and fast food consumption. Further, a previous study in Korea found prolonged internet use to be associated with less healthy dietary habits, including eating instant noodles and chips/crackers, among adolescents [25]. Relatedly, our study found that irregular patterns of meals during the pandemic were associated with increased fast food intake. A recent study of the dietary habits of Korean adolescents found that 29.2% of adolescents reported skipping breakfast, which was associated with increased smartphone use [26]. Especially during the pandemic, many students may miss out on regular diet as well as breakfast at home due to disrupted daily routines, including increased technology use. Our study suggests that students may have consumed fast foods as an alternative to regular meals during the pandemic. Furthermore, a study has reported that students have difficulty with weight control while at home compared to when they are in school [27] and increased intake of comfort and fast foods were associated with obesity. Therefore, during the COVID-19 pandemic, adolescents’ unhealthy food consumption patterns and irregular meals may have exacerbated risks for weight gain and obesity.
In terms of sleep, similar to other studies, we found that adolescents reported a significant increase in total sleep time during the pandemic compared to before the pandemic [28,29]. Teenagers in Korea experience more extreme sleep deprivation than those in other parts of the world due to early school start times and competitive academic pressure. Hence, the quarantine may have been an opportunity to increase their sleep time. However, our data also show a marked increase in technological device usage during the pandemic, and previous studies have consistently reported that this is associated with poorer sleep patterns among adolescents [30,31]. Thus, the interpretation that increased sleep time reflects healthy sleep quality cannot be verified.
This study also examined adolescents’ sleep patterns and eating habits during the pandemic. The results showed that irregular sleep patterns were associated with increased fast food consumption. Several studies have examined the association between short sleep duration and unhealthy dietary habits among adolescents [32,33]. The lockdowns during the COVID-19 pandemic might have forced children and adolescents to change sleep habits and reduced both the duration and quality of their sleep. In recent studies, adolescents have reported experiencing more sleep problems during the pandemic as compared to before, including insomnia, irregular bedtimes, and more napping [34]. Our study indicates that poorer sleep patterns accompanied by changing daily routines during the pandemic may have increased unhealthy dietary choices. However, some studies have pointed that eating fast food was associated with poor sleep quality [35,36]. Both sleep and eating habits are regulated by a complex interaction of neurotransmitters in the brain, such as serotonin and dopamine [37]. Hence, further studies are needed to verify a causal relationship between poor sleep quality and increased fast food consumption.
Finally, consistent with previous studies [38], we observed a decrease in physical activity among adolescents during the pandemic. This may stem from reduced outdoor activities due to stay-at-home orders and online learning. Our multivariable analysis also revealed that decreased physical activity was independently associated with fast food consumption. Previous studies have found sedentary behaviors (i.e., activities with low energy expenditure) to be associated with unhealthy dietary habits among adolescents, including lower fruit and vegetable intake and greater consumption of energy-dense snacks and fast foods [39,40]. Furthermore, low physical activity level and unhealthy diet are risk factors for major chronic diseases, including obesity [41]. Our results suggest that encourage physical activity and restriction fast food consumption may be important in preventing weight gain during the COVID-19 pandemic. Concerning the relationship between fast food and mental health, we found no significant association in the multivariable logistic regression analysis. Future work is needed to better understand the long-term negative effect of fast food on mental health. However, several longitudinal studies conducted with adults have identified a link between fast food consumption and depression [42]. Thus, future longitudinal studies of adolescents that explore the association between fast food consumption and depression risk are needed to implement effective strategies for reducing detrimental mental health outcomes.
This study has several limitations. First, as this was a cross-sectional study, we cannot ascertain the temporality of the associations between various lifestyle habits and fast food consumption during the pandemic. Second, because the survey was conducted after a long-term period of school closures and there was no specific time frame, response bias and recall errors may have occurred. Third, the use of subjective measurements to assess lifestyle habits during the pandemic could be subject to bias. Fourth, methodological limitations included the lack of consultation with a dietitian and no detailed education being provided to students regarding food related to the study. Fifth, the study was conducted on adolescents in one city; therefore, the results may not be generalizable to other populations. However, our study was a comprehensive assessment using a sizable Korean adolescent sample. Finally, in interpreting our results, how economic factors may have increased fast food consumption during the pandemic also needs to be considered [43]. Food insecurity, a condition in which households lack access to adequate food because of limited financial resources, is related to fast food consumption [44]. The COVID-19 pandemic had a considerable effect on the global economy by driving a drastic decline in total consumer spending compared to the previous year [45]. Thus, the relationship between economic status and fast food consumption among adolescents during the pandemic requires further exploration. Despite these limitations, this is a novel study in Korea that holistically examined the associations between lifestyle factors and fast food consumption in a large sample. In addition, although many lifestyle recommendations were made during the pandemic, both globally and nationally, our results extend the current knowledge on the need to improve school policies and parental awareness to implement effective interventions to ensure students maintain healthy eating habits during long-term school closures.
In conclusion, our results indicate that school closures have disrupted adolescents’ daily routines, including dietary habits, sleep patterns, and physical activity. These lifestyle changes during the pandemic were significantly associated with increased consumption of unhealthy foods, such as fast food, which may adversely affect long-term health. Parents and policymakers must pay close attention to changes in adolescents’ health following long school closures to prevent unhealthy lifestyle habits in the long run. Our study has important policy implications for increasing access to healthy food by providing relevant nutrition education and dietary guidelines to students during pandemic lockdowns. Given our findings that adolescent lifestyle changes during the prolonged pandemic period were associated with unhealthy eating habits, further studies on school programs that can help students manage a healthy lifestyle during school closures due to long-term crises are required.
