1. Introduction

The spread of the COVID-19 (SARS-CoV-2) pandemic all over the world has forced countries to handle the crisis in different ways, declaring a national state of alarm and establishing a mandatory home lockdown. The COVID-19 infection represents a strong stress stimulus, which has the capacity to induce high levels of perceived risk, fear, and anger, while forced quarantine at home may provoke an experience of boredom and loneliness, eliciting negative mental and behavioural responses in people ^[1]. It seems that the more time people remained at home, the more intense the resulting mental, emotional and lifestyle problems ^[2]. This situation has disrupted life and consequently altered multifaceted lifestyle behaviours. As a consequence, collateral damages of the pandemic are represented by inadequate nutrition with a risk of both overweight or underweight, addiction to screens, social isolation, disrupted sleep, and reduced physical activity with increased sedentariness: all these indirect effects of the COVID-19 outbreak have a potential mental health impact, particularly for vulnerable groups, and require effective and targeted measures.

2. Weight-Related Lifestyle Behaviors and the COVID-19

During the worldwide COVID-19 crisis and lockdown restrictions, behaviours that are health-protective against weight gain such as eating a healthy diet may be more difficult to achieve and maintain. A decrease in dietary diversification, with an aggravating effect of lockdown on disrupted consumption patterns, elevated symptoms of generalized anxiety disorder, decreased physical activity levels, and perceived weight gain have the effect of enhancing the risk of overweight and obesity ^[3]. More time at home may cause additional eating, along with sedentariness. Stress-related to fear and the continuous bombardment of news by the media about the spread of the pandemic may push one to consume so-called “comfort foods” (mainly composed of sugar or fats) or bring about a greater consumption of snacks between meals, with a consequent heightened risk of developing obesity ^[4]. In a cross-sectional survey conducted in the United Kingdom, 79% of participants reported a decline of at least one of five weight gain protective lifestyle behaviours studied (eating healthy, bingeing on food, exercising, sleep, alcohol consumption). In particular, subjects with a diagnosis of psychiatric illness or obesity resulted in an increased risk of weight gain during the COVID-19 crisis ^[5]. A web-based survey conducted in France suggests that weight gain may also be interpreted as the result of the observed increase in addiction-related habits (caloric/salty food intake, screen use, substance use) during lockdown ^[6]. Similarly, a Spanish study observed a rise in emotional eating during the months of confinement, “food craving” (the desire to consume a specific kind of food), and eating to compensate for boredom or anxiety with an increase in weight ^[7]. People living with obesity and mental health problems may have an increased risk of showing lifestyle behaviours associated with weight gain during the COVID-19 crisis ^[5]. It has been outlined that during a lockdown, a higher BMI (body mass index) was predictive of greater overeating and lower physical activity ^[8].

3. Sleep Disruptions Due to COVID-19

Sleep disturbances have affected a great number of people around the world during the COVID-19 pandemic lockdown. The loss of daily routines due to home confinement and the presence of change in work, family habits and financial concerns, the limited exposure to natural light, and reduced opportunities to exercise may have negative effects on sleep. Alterations in daily schedules have impacted circadian rhythms and energy balance with a significant repercussion of confinement on several external synchronizers of the biological clock ^[9]. More frequently observed sleep symptoms have been insomnia/disrupted sleep, daytime symptoms such as dozing off unintentionally in the day, difficulties falling/staying asleep, later bedtimes, abnormal behaviours in sleep, sleep-disordered breathing, restless legs, sleep phase disturbances, and nightmares ^[10]. Not only sleep quantity but also sleep quality was found to be compromised during the pandemic ^[11]. An Italian study found that more than half of the population had impaired sleep quality and sleep habits during the COVID-19 lockdown; related risk factors for poor sleepers were female gender, living in Central Italy, loss of a close one because of COVID-19 infection, changed sleep-wake rhythms, elevated levels of stress, anxiety, and depression ^[12]. A study conducted in South Korea has demonstrated that the total time participants spent sleeping was significantly higher than that before the pandemic; nevertheless, since satisfaction with sleep decreased, they may have had a poor sleep quality ^[13]. Particularly, in students, the increased use of social media applications led to a significant delay in falling asleep, usually at much later hours than usual, a lengthening of the duration of sleep and a general feeling of tiredness ^[14]. A reported impact on mental health (depressive symptoms and anxiety) was most strongly associated with more difficulties falling asleep, sleep disruption, nightmares, and daytime sleepiness. It has been suggested that worsening sleep quality may partly mediate the association between sedentary behaviours (physical inactivity, high TV viewing, high computer/tablet use) and mental health indicators (loneliness, sadness, anxiety) ^[15].

4. Consequences of COVID-19 Lockdown on Lifestyle Behaviors of Children and Adolescents

The closure of schools due to lockdown has reduced possibilities for physical activities and social life. Children and adolescents have been deprived for a long time of educational environments, social activities, and consequently contact with peers, with a disruption of daily schedules and a significant reduction of affective, cognitive, and physical stimuli. Decreased organized physical activity, increase in sedentariness, screen time, and consumption of caloric and sugary food with a consequent higher susceptibility to weight gain may enhance the great problem of childhood obesity ^[16].

In preschoolers, one has observed during quarantine a reduction of sleep efficiency, an increase in internalizing (i.e., antisocial behaviours) or externalizing problems (i.e., anxious or depressed behaviours), and a reduction of the total physical activity ^[17], while it has been demonstrated that higher levels of physical activity were associated with an improvement of the mood state among children and adolescents in the pandemic ^[18]. There is also concern about the finding that long periods of free-movement restrictions may negatively affect cardiorespiratory fitness in children and adolescents, a critical hallmark of health in youth, measured through a delay during COVID-19 confinement of the normal development of VO 2 max (maximal oxygen uptake). High levels of VO 2 max in childhood and adolescence are associated with lower values of cardiovascular risk factors (waist circumference, blood pressure, total cholesterol, body mass index) and lower odds of metabolic syndrome in later life; therefore, it is essential for youths to achieve sufficient levels of physical activity to preserve reliable health indicators ^[19].

In a cross-sectional study investigating the prevalence of lifestyle habits and mental health problems in Chinese adolescents during the COVID-19 pandemic, it has been observed that better nutritional patterns and moderate physical activity were both associated with lower levels of depressive and anxiety symptoms, while highly active physical activity was associated with lower levels of insomnia, depressive, and anxiety symptoms ^[20].

Sedentary behaviour may have serious consequences on existing and emerging psychopathology in children and adolescents, as it has been counted among possible risk factors for the development of insomnia, depression, anxiety, and psychosis ^[21]. The potential mental health benefits of maintaining a positive effect, engaging in physical activity and limiting leisure screen time have been highlighted for children during the pandemic, particularly for children with overweight/obesity ^[22]. There are some promising strategies to combat sedentary behaviour in youths, for example, the organization of public space options with individual physical distancing, exercise activities via live video conference calls, active-play video games that allow one to engage in indoor exercise activities, and above all adequate education for parents about the mental health benefits of regular activities ^[23]. A better understanding of students’ behavioural and socializing changes during COVID-19 lockdown results in being pivotal to programming critical and effective strategies for managing children’s mental health. Sleep and eating patterns, screen time, physical activity, and leisure seem to represent the most significant variables, influencing the many consequences of school closure and lockdown ^[24].

This entry is adapted from the peer-reviewed paper 10.3390/ijerph18168433