1. Introduction
On 31 December 2019, a new type of coronavirus appeared in the city of Wuhan (China) that infects and replicates in the pneumocytes and macrophages of the lung parenchyma, where the ACE-2 cell receptor resides, causing symptoms of fever, dry cough, lymphopenia, dyspnoea and pneumonia in its severe form that can lead to the patient’s death. This virus has been called SARS-CoV-2 or COVID-19 and only one month after its emergence in the Chinese city of Wuhan, the World Health Organization (WHO) declared it an international emergency disease [
1,
2]. The appearance of SARS-CoV-2 on the international scene, and in Spain in particular, led to the population being confined to their homes to prevent the spread of the virus. In Spain, 98 days of home lockdown were decreed between 15 March and 21 June 2020 for all people who did not have essential jobs, limiting by Royal Decree the movement of the population for essential activities [
3]. This great lockdown led to the closure of all educational establishments at all levels of education, from nursery schools to universities. Likewise, all schools and sports facilities were closed, so that the practice of any physical activity was reduced to the home. This unprecedented event, not only in Spain but also in other countries (e.g., Italy, France or Portugal), changed certain habits in the child and adolescent population. Habits related to the time dedicated to daily physical activity and the time spent using new technologies were modified [
2,
4].
Some indirect studies have determined by means of surveys that the school and adolescent population with obesity has changed their habits with the appearance of SARS-CoV-2 and has manifested itself in important health problems. The main health consequences were an increase in weight, an increase in comorbidities, an increase in BMI, statistically significant (
p < 0.05) parameters in laboratory results related to metabolic diseases and a general worsening of their health, regardless of SARS-CoV-2 status [
5]. In line with these studies, the present research aims to show that home lockdown and school closures due to the health crisis caused by SARS-CoV-2 have led to a significant decrease in physical activity, contributing to an increase in childhood and adolescent obesity, as well as to the appearance or worsening of their comorbidities.
At present, there are still few studies related to SARS-CoV-2 in pediatric patients (0–18 years). In Spain, the seroprevalence rate in the pediatric population is estimated to be 3.9% and 3.6% in Cantabria where the research sample is from [
6]. These seroprevalence data were obtained by stratified sampling by province and municipality size between 27 April and 11 May 2020, dates falling within the period of the great Spanish confinement. In the case of while the data in the pediatric population worldwide is estimated to be 1.56% [
7]. With regard to the incidence of clinical disease of SARS-CoV-2, the World Health Organization (WHO) publishes data worldwide, without a breakdown by age, so there are no official data from this institution for the pediatric population, which is also the case for data on the mortality rate due to COVID-19 [
8]. However, different epidemiological agencies in countries and regions of the world [
8] have begun to provide these data in a disaggregated manner, as is the case of the Spanish Ministry of Health, which presents data by age in its monitoring reports on the disease [
9].
In terms of risk factors for severe SARS-CoV-2 disease, age, arterial hypertension, cardiac or pulmonary problems, diabetes, cancer or obesity seem to be the most predisposing to severe disease according to the information provided by the WHO [
10,
11,
12]. Childhood obesity and overweight can have repercussions on children’s health throughout their lives, hence the importance of working on the prevention of this disease and the acquisition of healthy habits. However, given the prevalence of childhood overweight and obesity in Spain, it may be one of the most important risk factors in the pediatric population [
13]. For this reason, changes in anthropometric parameters, as well as in dietary habits and physical activity, may accentuate this risk factor. In addition, children infected with COVID-19 have been identified as having significantly lower vitamin D levels than the pediatric population not infected with COVID-19 [
14], a vitamin that is essential for muscle and bone function related to physical activity [
15].
In this context, the main factors in the incidence of overweight and obesity in children are sedentary lifestyles and excessive time spent using technology. These factors have led to 85% of school-age girls and 78% of school-age boys not performing the minimum minutes of daily physical activity established by the WHO for their age range [
16]. These factors, together with inadequate eating habits, in which ultra-processed foods abound, lead to an obesogenic environment in children that causes an increase in overweight and obesity rates [
4,
17].
The WHO establishes at least 60 min of moderate to vigorous physical activity (MVPA) per day for children, and the time that exceeds this amount will result in greater health benefits for the child. This institution also recommends that children aged 5–12 can be exposed to screens and new technologies in between 60 and 90 min per day [
16,
18]. However, the school population is far from complying with these WHO recommendations. Between the ages of 9 and 15 years, there is a greater sedentary time and a decrease in physical activity outside the school context, especially in girls and in schoolchildren who are already overweight or obese compared to schoolchildren with Body Mass Index (BMI) values in the normal range [
19].
These low levels of physical activity among schoolchildren and excessive time spent using new technologies, known as the “technological sedentary lifestyle” [
4,
20], aggravate health problems due to childhood overweight and obesity and cause other health problems, such as isolation of children, poor social relations, sleep disorders, endocrine, musculoskeletal and/or cardiovascular problems [
17].
The WHO points out that it is in developed countries where overweight and obesity are the most worrying and most prevalent metabolic problem among the population, calling it the “epidemic of the 21st century” [
21]. The prevalence of overweight in children between 6 and 9 years old is 23.3%, and it is 17.3% in the case of obesity, of which 4.2% refers to severe obesity. The data show an upward trend during the school years [
22]. The main consequences are an increased risk of mortality, worsening anthropometric parameters and poor physical fitness [
23]. They can also lead to cardiovascular problems, diabetes or non-communicable diseases in children and adolescents [
22,
24,
25].
Prior to the appearance of COVID-19 in Spain, a study was already underway, and programmed data were collected, which, together with a collection of post-confinement data, have made the present research possible. For these reasons, the main aim of this study was to find out the impact that the large-scale lockdown due to SARS-CoV-2 had on anthropometric parameters in the population of 11/12-year-old children. The relationships between these anthropometric parameters, dietary habits and sociodemographic data (e.g., type of housing, place of residence or time spent in physical activity) were also studied. In this research, the anthropometric parameters established in the Body Dimension of the Alpha-Fitness Battery [
26].
2. Materials and Methods
2.1. Study Design
In order to carry out this research, a longitudinal observational study was conducted [
27]. The dependent variables of this research were the anthropometric parameters of weight, height, waist circumference, triceps skinfold and subscapular skinfold. These parameters were taken according to the Alpha-Fitness Battery, a validated field test for the assessment of health-related physical fitness in children and adolescents [
26]. The independent variables were obtained from a validated instrument to assess food consumption, habits and practices in children aged 8–11 [
28] and from an ad hoc survey for parents to collect sociodemographic data on the family and data on the different variables under study.
2.2. Participants
The sample selected for this research was of a non-probabilistic sample of convenience nature from a primary school in Cantabria (Spain).
A total of 55 children in the sixth year of Primary Education at a school were invited to participate, of which 5 students did not wish to take part in the research for various reasons or because they did not have the informed consent of their parents or legal guardians. The sample finally consisted of 50 schoolchildren between 11 and 12 years of age (M = 11.40; SD = 0.50), 33 (66%) boys and 17 (34%) girls. Fifty-six percent of the sample resided in an urban setting, while 38% resided in a semi-urban or residential setting and 6% in a rural setting.
2.3. Tools
The Alpha-Fitness Battery, a validated field test for the assessment of health-related physical fitness in children and adolescents, was used for data collection [
26]. The Alpha-Fitness Battery consists of five dimensions: Dimension 1, Tanner Stage (3 items); Dimension 2, Body Composition (5 items); Dimension 3, Musculoskeletal Capacity (3 items); Dimension 4, Motor Capacity (1 item); and Dimension 5, Aerobic Capacity (1 item). For this study, Dimension 2 was used, consisting of five items referring to Body Composition and its reference values [
29]: weight (kg), height (cm), waist circumference (cm), triceps skinfold (mm) and sub-scapular skinfold (mm). Measurements were taken by a Holtain mechanical plicometer with a measuring range of 0 to 48 mm and a constant pressure of 10 g/m
2 mm. A Garmin Index S2 scale, a Seca 2016 measuring rod with a range of 10–230 cm and 1 mm division and a CESCORF anthropometric measuring tape 6 mm wide and 2 m long were also used. The procedure used for the measurement of the anthropometric variables was the one established in the International Standards for Anthropometric Assessment of the International Society for the Advancement of Kineanthropometry [
30]. BMI and body fat percentage values were obtained by measuring these variables. For their calculation, the formula BMI = kg/height in m
2 was used, while for the calculation of body fat percentage, the equations of Slaughter et al. (1988) were followed [
31].
For the collection of information on eating habits, a validated instrument was used to assess food consumption, habits and practices in children aged 8–11 [
28]. This instrument is made up of 42 items distributed in five sections: frequency of food consumption, cooking skills, eating habits, expenditure on food in the school environment and knowledge.
An ad hoc survey consisting of 50 items was also used for parents or legal guardians. It was used to collect sociodemographic data on the family, time spent on physical activity before and during lockdown, time spent on sedentary activities and the use of new technologies and emotional aspects during lockdown.
2.4. Procedure
The aim of this research is to find out the impact that lockdown due to SARS-CoV-2 had on anthropometric parameters in the 11/12-year-old population. The research has its origins in a broader investigation that aimed to carry out a comparative analysis between two groups of sixth year primary school children with respect to anthropometric parameters; physical condition; psychological and emotional aspects, such as anxiety; and academic results. Data collection was scheduled to take place at three points during the academic year. The first two data collections were carried out as planned in physical-education classes [
32] during the weeks of 14 October 2019 and 2 March 2020 (
Figure 1).
However, the third data collection, due to the outbreak of SARS-CoV-2 in Spain, could not be carried out at the scheduled time. This outbreak led to a major house lockdown in Spain from 15 March 2020, decreed by the Spanish State by means of a State of Alarm. During this lockdown all educational centers in Spain are closed indefinitely [
3]. This is why the third data collection was carried out immediately after the end of this major lockdown and during the de-escalation period from 28 May 2020 (
Figure 1). In order to guarantee the sanitary measures established by the Spanish government for the prevention of SARS-CoV-2 infection, the sample was convened in groups of 6 children at different times and in an open-air space.
Both the initial study and its modification followed the processes established at the administrative and ethical level for research with schoolchildren: authorization by the educational centers and the Inspection Service, an informative meeting with the families or legal guardians who constituted the research sample and changes in the established schedule. At this meeting, the objectives and process of the research (data collection, analysis techniques and use of the data collected), the confidentiality of the participants, the voluntary nature of the study and the possibility for their children to leave the study at any time they wished without the need to justify their withdrawal from the study were explained. All this information was given to the families in writing, together with the informed consent form.
2.5. Statistical Analysis
SPSS statistical software (SPSS v.26, IBM Corporation, New York, NY, USA) was used to perform all the statistical analyses of the study. A descriptive analysis of the main variables under investigation was carried out, as well as normality tests of quantitative variables for the testing of hypotheses. The Kolmogorov–Smirnov statistic (n > 50) was used for the normality analyses of the whole sample, while the Shapiro–Wilk statistic (n < 50) was used for the normality tests by sex. When the p-value of the normality tests was significant (p < 0.05), the hypothesis that the variable does not have a normal distribution was accepted.
For the hypothesis testing, different tests of independence have been used depending on the nature of the variables and certain assumptions that must be fulfilled in order to apply them. Whether the quantitative variable is normally distributed in the different categories of the qualitative variable (parametric tests) or whether it is non-normally distributed in the different categories of the qualitative variable (non-parametric tests), the type of test will also depend on whether the categorical or qualitative variable has two or more than two categories. For parametric tests, when the categorical variable has two categories, the Student’s t-test was used, and if it has three or more categories, the comparison of means was carried out through the analysis of variance ANOVA. In the non-parametric analyses, when the categorical variable has two categories, the Mann–Whitney U test was used, and if it has three or more groups, the Kruskal–Wallis test was used. The Student’s t-test for paired samples was also used to check if there is a statistically significant difference (p < 0.05) between the data obtained pre-lockdown and post-lockdown of the study variables, in case the assumption of normality was met, if there was no normality, the non-parametric Wilcoxon rank test was used. For independence between qualitative variables, the chi-square test of independence was used.
Finally, to test for correlation or association between quantitative variables, two tests were used depending on whether their distribution is normal or not. When the distribution of both variables is normal, Pearson correlation was used; otherwise, Spearman correlation was used.
2.6. Ethical Aspects
The ethical and deontological principles established by the American Psychological Association [
33], as well as the ethical recommendations for educational research [
34], were followed in all phases of the study.
Approval of the research protocol was requested from the EDUCA Ethics Committee, which was approved under code 82019.
4. Discussion
The aim of this study was to determine the impact that lockdown due to SARS-CoV-2 had on anthropometric parameters in children aged 11/12.
This study showed results between pre-lockdown and post-lockdown that show changes in anthropometric values outside the expected standardized values for height, weight and BMI [
26,
31]. The results show a decrease in BMI and body weight and an increase in waist circumference, body fat percentage and skinfold parameters. Likewise, this research has shown that the habits in relation to physical activity and eating habits were modified by the sample during the period of lockdown. In relation to physical activity habits, there was a decrease in the number of minutes per day, as well as in the weekly frequency of physical activity. In terms of dietary habits, the number of meals per day increased, as well as the intake of foods rich in saturated fat and sugars. The results show worse values for anthropometric parameters in boys than in girls, as well as in study participants who lived in small dwellings without a garden during confinement and in children whose parents were less educated.
Furthermore, different studies show that children and adolescents do not comply with the recommendations regarding physical activity and sedentary behavior [
36], which together with the changes in habits brought about by the health crisis created by COVID-19 [
4,
37,
38] may lead to increases in anthropometric parameters and accentuate problems of overweight and obesity. The percentages of children who exceed the minutes of screen time recommended by the WHO [
16] are high and together with the time spent in other sedentary activities, favor an increase in the rate of overweight and obesity. Finally, the number of hours of sleep per day is also an important factor favoring changes in anthropometric parameters [
39,
40]. The WHO recommendation for hours of sleep per day in children aged 6 to 12 years is at least 11 h.
This research also shows that the changes in habits produced by the lockdown due to SARS-CoV-2 [
4,
37,
38,
41] have had an influence on eating habits, leading to a greater number of meals per day, as well as an increase in the intake of foods rich in saturated fats and sugars, which also favors an increase in anthropometric parameters and the appearance of childhood overweight and obesity [
42,
43].
This research also confirms that the time dedicated to physical activity during lockdown does not reach the minimum time recommended by the WHO [
18,
44], which has also favored changes in anthropometric parameters, as shown in the results obtained for anthropometric parameters in relation to the time and frequency of physical activity before and after lockdown.
Therefore, this research confirms that environmental variables were the main causes of anthropometric changes in the study sample. Numerous research studies and institutions have found that environmental variables are the main factors in the increase of obesity and overweight rates in healthy populations [
45,
46,
47].
This study shows that anthropometric parameters according to reference values [
29,
31] have been modified between pre-lockdown and post-lockdown due to SARS-CoV-2, because of a multifactorial cause. These changes in anthropometric parameters are more accentuated in the case of boys, with the value of some parameters being high. However, the results obtained do not show any evidence of childhood obesity problems in the sample [
48]. It should be noted that, after lockdown, the anthropometric parameters of weight and the BMI of the sample decreased, while the parameters of skinfolds and body fat percentage increased. These changes are due to the long period of physical inactivity or the lack of physical stimuli produced in the body during lockdown [
49,
50,
51]. Tests performed to verify the relationships between anthropometric variables have shown very high correlations between pre-lockdown two and post-lockdown in the anthropometric variables of waist circumference, in the different measurements of subcutaneous folds and in the percentage of body fat. This increase in body fat disproportionate to the normal growth of the child may be due to the impact of environmental variables on the modification of anthropometric parameters during SARS-CoV-2 lockdown [
52,
53].
Until the outbreak of SARS-CoV-2, different reports and organizations had already noted the high levels of childhood overweight and obesity in Spain, i.e., 23.3% and 17.3%, respectively [
54,
55], and their association with other pathologies, such as cardiovascular diseases, metabolic diseases, cancer or hypertension, among others, which can manifest themselves in childhood and adolescence or appear in adulthood [
56,
57,
58,
59]. These diseases associated with childhood overweight and obesity may become risk factors in the event of SARS-CoV-2 infection [
13,
41,
60,
61]. The large Spanish lockdown may have favored the increase of these values of childhood overweight and obesity.
5. Conclusions
Based on the results obtained in this research, it is concluded that there have been significant changes in the anthropometric parameters of 11- and 12-year-old boys and girls in an educational Centre in Cantabria (Spain) as a result of the impact of the lockdown due to SARS-CoV-2. These changes may have had a multifactorial origin in which an excess of screen time, changes in eating habits and a decrease in physical activity time during lockdown have predominated. In relation to gender, these changes have been more significant in boys than in girls. However, it should be noted that one of the limitations of the research is the difference in sample size by gender. Another limitation of the study is the size of the sample, which is why it is not possible to generalize the results of the study to the population aged 6–12 years. However, it should be noted that, taking into account the aforementioned studies, as well as the results of the latest survey of the Spanish National Institute of Statistics (INE) in 2020 [
62] used for the elaboration of the EUROSTAT reports [
63], a similar prevalence is observed between the convenience sample of this study and the general population in relation to the rates of overweight and obesity, the values of physical activity practice and eating habits. Despite the fact that all anthropometric parameters have increased, values of childhood obesity have not been reached.
This research has shown the need to continue strengthening and promoting effective strategies to encourage the practice of healthy and regular physical activity, the acquisition and maintenance of healthy eating habits and the responsible use of technology, especially in situations such as the large-scale lockdown due to SARS-CoV-2. There is an urgent need to design and implement a strategic plan due to the negative consequences that the lockdown has had on the child and adolescent population in terms of anthropometric parameters. It would be desirable for the health authorities, educational institutions and the family environment to participate in this plan.