Gender Differences in Eating Habits, Screen Time, Health-Related Quality of Life and Body Image Perception in Primary and Secondary School Students: A Cross-Sectional Study in Spain

Abstract

The decline in quality of life in recent decades in Spain and how it is related to health factors highlight the importance of considering health-related quality of life (HRQOL) as a key indicator in the assessment of well-being. Marked by physical, hormonal and social changes, adolescence is a critical period when lifestyle habits are consolidated, including physical activity and diet, which affect HRQOL. There are growing concerns that body image, especially in a context of increased sedentarism and screen use, is associated with low self-esteem and mental health problems. The promotion of healthy habits and a positive body image during this age is essential to improve overall well-being and prevent psychological disorders. This study examines differences in screen time, Mediterranean diet adherence, health-related quality of life and body image self-concept in children and adolescents, considering gender and educational level. A cross-sectional analysis was conducted with 305 students (ages 11–14) from primary and secondary schools. The instruments used to measure the different variables were the KIDMED questionnaire for adherence to the Mediterranean diet, the Screen-time Sedentary Behaviour Questionnaire (SSBQ) for screen time, the KIDSCREEN for health-related quality of life and the Body Size Guides (BSGs) for body image perception. The results showed significant differences by educational stage in screen time, health-related quality of life and body image, with secondary school students reporting higher values. No significant differences were found based on sex. The originality of this study lies in its holistic approach to identify patterns of behaviour and well-being, influenced by sociocultural and demographic factors, and in the detailed analysis of variations by age and gender that affect physical and mental health during critical stages of development. The findings highlight the need for educational strategies to promote healthy lifestyles, involving students, families and their environments, to enhance well-being and self-esteem.

1. Introduction

The World Health Organization (n.d.) defines quality of life (QOL) as an individual’s perception of their position in life in the context of the culture and value systems in which they live and in relation to their goals, expectations, standards and concerns (World Health Organization, n.d.). QOL can be said to be subjective and multidimensional (Cesnales & Thyer, 2023; Lam, 2010).

With the idea of delving deeper into the definition of QOL and contributing factors, the concept can be applied to different areas. This gives rise to the secondary concept of health-related quality of life (HRQOL), which refers to the degree of well-being derived from a personal assessment of different areas of one’s life, taking into account the influence that their state has on them (Urzúa, 2012). This concept focuses on how physical and mental health impacts a person’s overall well-being (Bakas et al., 2012).

The autonomy and QOL of a person are directly associated with the lifestyle variable. In general, a lifestyle is considered healthy if, in its context, it results in a lower probability of disease and disability (Honório et al., 2021).

However, there is a significant discrepancy with regard to the knowledge of the elements of a healthy lifestyle, such as a balanced diet and regular physical activity, and its practical application. Changes in social values have led to increased self-responsibility for health, motivating individuals, especially young people, to seek information and products that promote well-being. However, this often shifts the focus toward physical appearance rather than health itself (Svensson & Hallberg, 2011).

This study analyses different factors that influence the QOL and health of children and adolescents, with HRQOL as a transversal axis. Key variables include sex and educational stage, particularly the transition between primary and secondary education. These variables reflect the sensitive developmental period in which the study sample is situated.

This period of transition to secondary school can have immediate effects on children’s behaviour, in part due to differences in environmental characteristics (Chong et al., 2020). The transition from primary to secondary school is a period that involves many changes that affect the lifestyle habits of children and adolescents. The increase in screen time, in a period of transition to greater independence, is one of them, thus affecting the increase in sedentary time at this transitional stage (Pearson et al., 2017). This period is considered to be one of academic and social inflection, in which one’s concern for social acceptance rises, which can lead to a loss or weakening of self-esteem. All the factors involved at this stage have an impact on the social-emotional and behavioural development of children and adolescents (Hanewald, 2013).

The adolescent stage is complex for both sexes. Teenagers are subject to pressures and concerns about their physical attractiveness, with boys being concerned about physical condition and girls about their appearance and body weight, which makes it necessary to evaluate these differences by sex in order to assess, discover and act on them (Castrillo et al., 2021). In addition, adolescence is a critical period characterised by morphological and hormonal changes (Anton-Păduraru et al., 2021). This transition is associated with changes in lifestyle, including physical activity (PA) and sedentary behaviour, which are two important factors for maintaining good health throughout life (Vanhelst et al., 2023).

Furthermore, this is a period characterised by a growing tendency towards independence and a preoccupation with personal image (Anton-Păduraru et al., 2021). The latter consists of two perceptual dimensions: body dissatisfaction with respect to weight and physical appearance. The scientific literature has revealed that body dissatisfaction in adolescents is linked to body fat percentage and weight and is associated with low self-esteem and different medical, mental and social problems (Gomes et al., 2021; Singh & Manju, 2022). The trend towards a sedentary lifestyle is associated with a greater concern for body image (Gomes et al., 2021), while studies such as those by Sollerhed et al. (2022) relate the well-being of adolescents to a positive conception of body image. Forming a positive body image during the teenage years is crucial, as it has been shown to contribute significantly to psychological well-being and the prevention of psychological disorders such as anxiety, depression and suicidal tendencies (Palenzuela-Luis et al., 2022).

Health-related QOL can be predicted to a large extent by the satisfaction of an adolescent (with their life, with their family and friendships) and their PA practice, as well as that of their family and friends (Urchaga et al., 2020). However, there are studies that show that many teenagers do not follow many dietary and physical activity recommendations (Mokari-Yamchi et al., 2024; Pearson et al., 2009).

Studies such as that of Solera-Sanchez et al. (2021) reveal that adolescents who practise more than three health-related behaviours have higher levels of HRQOL than their peers who do not practise any. A high perceived HRQOL in children and adolescents is related to having a healthy lifestyle, being in good physical condition and being of a normal weight. Those who had a high perceived HRQOL met daily recommendations for fruit and vegetable consumption and screen time (Ródenas-Munar et al., 2023).

This new era in which we find ourselves has meant that much of the leisure time enjoyed by children and young people involves being in front of a screen (Grams et al., 2022). The prevalence of sedentary behaviour, especially in the context of technology-based leisure activities, contravenes the WHO guidelines (World Health Organization, 2020). According to these guidelines, children and adolescents should engage in at least 60 min of moderate to vigorous physical activity per day, including at least three days per week of vigorous-intensity aerobic activities that strengthen their muscles and bones. Time spent on sedentary activities should also be limited, especially leisure time in front of a screen, which should be less than two hours a day to mitigate the associated physical inactivity.

In Spain, the level of non-compliance with the recommendation for screen use is much higher than stipulated, with a greater prevalence at the weekend and increased screen use in males and during adolescence (Gómez et al., 2023).

Changes in lifestyle, the accessibility to processed food and the high price of ‘natural’ products have led to an increase in the number of people eating an inadequate diet (World Health Organization, 2018). A decline in the Mediterranean diet among Spanish children and adolescents has been observed over the last 20 years, with adverse long-term health consequences (Herrera-Ramos et al., 2023). The adoption of healthy eating habits is associated with improvements in other aspects that affect QOL (Knebel et al., 2022). Different studies relate low adherence to the Mediterranean diet with screen time, both in children and adolescents (Wärnberg et al., 2021), and following the recommendations for FA and screen time has been related to optimal adherence (Bibiloni et al., 2022).

The literature supports the idea that lifestyle patterns established in childhood influence health and well-being in later stages of life (Dumuid et al., 2017). Lifestyle contributes to the development of chronic non-communicable diseases, currently the leading cause of death. Therefore, it is imperative to develop instruments to assess the state of one’s self-concept, self-perception, physical exercise and lifestyle (Palenzuela-Luis et al., 2022).

The aim of this study was to evaluate the differences in screen time, adherence to the Mediterranean diet, perception of body image and health-related quality of life between males and females and between primary and secondary school students. We seek to describe the associations between the variables by means of a correlational analysis.

Numerous studies have analysed the perception of body image, healthy eating habits, screen time and the perception of health-related quality of life based on sex, both at the international level (Christofaro et al., 2016; Esposito et al., 2022; Heiman & Olenik-Shemesh, 2019; Vilugrón Aravena et al., 2020; Yan et al., 2017) and within the national context (Ramos et al., 2019; Ródenas-Munar et al., 2023). However, the majority of these studies tend to focus on individual aspects or partial combinations of these factors rather than analysing them in a comprehensive and integrated manner. There is a notable lack of research adopting a holistic approach that examines these aspects collectively and explores their interactions within the adolescent population.

On the other hand, it is important to promote the connection between age and all the variables mentioned previously, and it is necessary to dedicate special attention to critical periods of growth and the development of habits, such as the transition from primary to secondary school. As we have already seen, this transition period represents for students a maturation process that involves different social, academic and personal changes, influencing their vital development (Ávila Francés et al., 2022; Folgar et al., 2013).

In addition, there are numerous studies that confirm how this period is characterized by the assumption of unhealthy behaviours, such as a decrease in sports practice (Estévez Gómez & Hoyos Cuartas, 2021; Fernández Guerrero et al., 2019; Guevara et al., 2019; Ridley & Dollman, 2019; Zurita-Ortega et al., 2018), a lack of motivation for such practice (Franco Arévalo et al., 2023), an increasingly sedentary lifestyle (Lamoneda-Prieto & Huertas-Delgado, 2017) or a decreased perception of health-related quality of life (Nuviala Nuviala et al., 2010), among other factors.

The usefulness of this type of study lies in its ability to identify patterns of behaviour and well-being that may be influenced by both sociocultural and demographic factors. Additionally, by examining the variations between different age and gender groups, this study offers a deeper understanding of how these interrelated factors affect physical and mental health during critical stages of development, such as childhood and adolescence.

The holistic approach proposed in this research is essential to better understand the factors affecting the well-being of youth and to develop more effective interventions that promote healthy lifestyles and positive self-perceptions. For this reason, it is essential to carry out studies such as the present one, with large samples of children and adolescents that allow us to learn about the evolution of this problem throughout this transition period (Ortiz-Sánchez et al., 2024).

The results may help in the creation of personalised intervention programmes, as well as in the design of more effective public health policies adapted to specific needs, with the potential to serve as a model for similar studies and strategies in other regions. Likewise, scientific evidence is offered in the Spanish context, contributing to the development of health promotion strategies more adapted to the educational and social reality of the country.

2. Materials and Methods

2.1. Design

This study follows a descriptive, cross-sectional, multi-centre design. The study was conducted using a descriptive survey methodology.

2.2. Participants

The study sample is an integration of students from public primary and secondary schools in the municipality of Oleiros (A Coruña). This area is characterized by a process of transformation from a rural area to a high-level residential area, with a high per capita income. According to the latest update of the Galician Institute of Statistics, Oleiros is the Galician municipality with the highest municipal household income per inhabitant (23,238 EUR—2020), with an area of 43.8 square kilometres and a population of 37,271 inhabitants. Likewise, there is a wide variety of public services and infrastructures, such as numerous sports facilities and clubs, and municipal and school programs aimed at promoting health. These characteristics, with the added advantage of being surrounded by a very diverse natural environment, could indicate its inhabitants are more able to practice sports, physical activity or healthy routines that allow them to achieve a higher quality of life. In any case, it should not be forgotten that the growth of this population and its diversity also pose challenges when it comes to the distribution of services or the adaptation of the education offered in the school community.

Table 1. Sample characteristics by academic year and sex. Frequency and percentage of the sample.

Students (n)				Frequency and Percentage
6th Year Primary Education		2° ESO		Girls	Boys	6th Year Primary Education	2° ESO
Girls	Boys	Girls	Boys
73	94	68	70	141 (46.2%)	164 (53.8%)	167 (54.8%)	138 (45.2%)

presents the distribution of students by educational level and sex. In 6th year of primary school, a total of 73 girls (46.2%) and 94 boys (53.8%) participated in the study. In contrast, in 2nd year of secondary education (ESO), there were 68 girls (54.8%) and 70 boys (45.2%). These data indicate a relatively balanced gender distribution at both educational stages.

2.3. Study Variables

Dependent variables were as follows: adherence to the Mediterranean diet, screen time, health-related quality of life and self-concept of body image.

Independent variables were as follows: educational level (sixth year of primary education and second year of secondary education) and sex.

2.3.1. Adherence to the Mediterranean Diet

The Mediterranean diet is a precious cultural heritage embodied in a rich and healthy dietary pattern. This was recognized by UNESCO in 2013 when it was included in the Representative List of the Intangible Cultural Heritage of Humanity (UNESCO, 2013). It is characterized by the following key guidelines: using olive oil as the main added fat; consuming abundant amounts of plant-based foods; incorporating bread and cereal-based foods as part of one’s daily diet; prioritizing fresh, seasonal, and minimally processed meats in small amounts; eating plenty of fish and moderate amounts of eggs; choosing fresh fruit as one’s usual dessert; reserving sweets and pastries for occasional consumption; drinking water as one’s primary beverage; and consuming wine in moderation during meals (Fundación Dieta Mediterránea, n.d.)

The instrument used in this study to assess adherence to the Mediterranean diet was the KIDMED questionnaire.

2.3.2. Screen Time

Screen time is defined as the period spent using electronic devices such as televisions, computers, tablets and mobile phones for recreational, academic or work-related purposes (Rocka et al., 2022). In the context of children’s and adolescents’ health, this concept has been associated with low adherence to the Mediterranean diet and an increased risk of overweight and obesity (Crowe et al., 2020; Rocka et al., 2022; Wärnberg et al., 2021).

Furthermore, excessive screen time is linked to risk behaviours, such as substance use, violent behaviour, unhealthy eating habits and poor academic performance (Hamrik et al., 2015).

Screen time was measured using the Screen-time Sedentary Behaviour Questionnaire (SSBQ) (Rey-López et al., 2012), following the criteria established in the Healthy Lifestyle in Europe by Nutrition in Adolescence (HELENA) study.

2.3.3. Health-Related Quality of Life

Health-related quality of life is a subjective concept, conditioned by the cognitive processes related to the evaluation that each person makes of their objective living conditions and their degree of satisfaction with each of them (Cantó et al., 2021). The perception of health depends not only on physiological qualities, but also on personal experiences, the cultural context and the family environment, among others. The term self-perception of health status is understood as the information provided by the subject about their health status as a result of their knowledge and interpretations (Jaimes-Valencia et al., 2019).

HRQOL or perceived health covers aspects of life directly related to one’s state of well-being regarding physical and mental functioning, which can be differentiated into the following: physical state and functional capacity; psychological state and well-being; and social interactions, economic status and its factors (Soto & Failde, 2004).

Health-related quality of life was evaluated using the KIDSCREEN-10 questionnaire (Gomez et al., 2014).

2.3.4. Self-Concept of Body Image

Body self-esteem is a multidimensional construct relating to the self-perception of your own body and appearance. This includes factors such as physical attractiveness, physical condition and weight concerns. Adolescents with a poor perception of their body and appearance are therefore at greater risk of developing low self-esteem and depression (Cragun et al., 2013).

The main driver of body dissatisfaction is sociocultural influence, based on which young people strive to meet or adapt to aesthetic standards (Gomes et al., 2021). There is a positive relationship between the perception of health and physical self-concept, so that an increase in the latter will influence one’s perception of health, affecting the quality of life of young people and future adults (Castrillo et al., 2021).

To analyse the general body image assessment of the study subjects, the perceptual component evaluation tool Body Size Guides (BSGs) by Harris, Bradlyn, Coffman, Gunell and Cotrell was used. This is one of the body silhouette tests commonly applied in adolescents (Cuervo et al., 2017; Harris et al., 2008).

2.4. Data Collection Tools

2.4.1. KIDMED Index

Adherence to the Mediterranean diet was assessed using the KIDMED questionnaire, originally developed and validated by Serra-Majem et al. (2004) to estimate adherence in children and young adults based on the principles underpinning Mediterranean dietary patterns. This questionnaire consists of 16 items with a yes/no answer. Items denoting low adherence are scored −1 (4 items), while those related to high adherence are scored +1 (12 items). Therefore, the KIDMED index score ranges from −4 to +12 points. The KIDMED index was used to classify participants into three categories: low adherence (0–3 points), medium adherence (4–7 points) and high adherence (8–12 points) (Gómez et al., 2023).

The KIDMED index has been shown to be a reproducible and reliable tool for evaluating adherence to the Mediterranean diet. It has been widely used in studies assessing dietary habits in children and adolescents. Notably, the HELENA study identified the KIDMED index as one of the most appropriate and valid tools for evaluating Mediterranean diet adherence among European adolescents (Rei et al., 2021).

2.4.2. Screen Time

Screen time was assessed using the Screen-time Sedentary Behaviour Questionnaire (SSBQ) (Rey-López et al., 2012), based on the screen time of the study Healthy Lifestyle in Europe by Nutrition in Adolescence (HELENA). This study is based on the analysis of the time spent per day performing four activities: watching television, playing on the computer, playing video games and using a mobile phone, differentiating between weekdays and weekends (Wärnberg et al., 2021). To calculate the average daily time, the weighted average was calculated for weekdays (five days) and weekends (two days). The response scale used was as follows: (1) never, (2) 0–30 min per day, (3) 30–60 min per day, (4) 1–2 h per day, (5) 2–3 h per day and (6) more than 3 h per day. The number of minutes of sedentary behaviour per day was calculated as follows: category 1 = 0 min, 2 = 15 min, 3 = 45 min, 4 = 90 min, 5 = 150 min and 6 = 210 min (Rey-López et al., 2012).

The HELENA questionnaire has proven to be a reliable questionnaire to use with adolescents, with good to excellent reliability. Test–retest reliability has been evaluated using weighted (quadratic) Cohen’s coefficients (Rey-López et al., 2012).

2.4.3. Health-Related Quality of Life

Health-related quality of life was measured using the KIDSCREEN-10 questionnaire (Gomez et al., 2014). This questionnaire is the shortest version of the KIDSCREEN questionnaires and measures general health-related quality of life (HRQOL) (Kidscreen, n.d.).

The questionnaire consists of 10 items. The response options for each item are as follows: never, a little, moderately, considerably and a lot (Gomez et al., 2014). Subsequently, a total score is calculated for the scale using all the item scores, taking into account that the additional item on general health should not be included. This will give a value between 10 and 50, in which 10 is the lowest possible value and, therefore, a very low health-related quality of life, and 50 is the maximum, i.e., a very high health-related quality of life.

The Spanish version of this tool has acceptable preliminary reliability and construct validity. The dimensions of the questionnaire have presented an internal consistency of ≥0.7, the minimum figure recommended for the use of the questionnaire in groups. Consequently, it can be concluded that the KIDSCREEN, an instrument for assessing HRQOL, presents good reliability, validity and acceptability to be applied in the adolescent and child population in general (Aymerich et al., 2005).

2.4.4. Perception of Body Image

This study used the perceptual component evaluation tool Body Size Guides (BSGs) by Harris, Bradlyn, Coffman, Gunell and Cottrell to conduct a general body image assessment of our study subjects, being one of the body silhouette tests used in adolescents (Cuervo et al., 2017; Harris et al., 2008). Studies confirm that the best methods for global estimation of body image are silhouettes or figure scales, in which the subject chooses the one they think best represents them (Cuervo et al., 2017). The students had to indicate which body shape they most identified with from the 10 images provided.

Psychometric analyses indicated that BSGs are valid and reliable instruments (Harris et al., 2008). According to this instrument, option A indicates a weight below normal, options B and C indicate a normal weight, D represents overweight, E and F represent class I obesity, G and H represent class II obesity, and I and J represent class III obesity.

2.5. Procedure

The data were collected in January 2022 in five primary schools and three secondary schools. Informed consent was obtained in advance, signed by the parent or legal guardian of each participant.

An average of one visit per centre was made, with the possibility of additional visits if necessary to ensure the development and effective conclusion of the process. All data were collected during school hours, using an online form, or a physical form in the case of centres that did not have electronic devices. Two members of the research group were present in every centre throughout the process to ensure that the participants understood all the questionnaires.

The study population consisted of 543 subjects, 273 in the second year of ESO (Spanish compulsory secondary education) and 270 in the sixth and last year of primary education. As for the sample selection procedure, non-probabilistic quota sampling was used, and size was defined according to a confidence level of 95% (Z = 95%) and a margin of error of 3.73 (e = 3.73). All participants met the inclusion criteria, although 13 were eliminated for not filling in the paper questionnaire correctly. For the selection of the sample, the following inclusion criteria were taken into account: the students had to be enrolled in one of the public schools in the municipality of Oleiros; they had to belong to the academic years under study; and they had to be present during the data collection process. Likewise, the informed consent of their parents had to be obtained in order for them to participate in the study. As for the exclusion criteria, students who did not meet the above criteria were eliminated, as well as those participants who did not adequately complete all the required variables, thus ensuring the integrity and validity of the data collected. Finally, a sample of 305 subjects was obtained.

The study project was submitted for evaluation to the Ethics Committee of the Faculty of Education and Sport Sciences of the University of Vigo. The approval code is 07-181223.

2.6. Statistical Analysis

The statistical analysis performed is based on a descriptive and inferential approach that compares the variables according to sex and educational level. To characterise the central tendency of the data, mean values were calculated and, to evaluate dispersion, the standard deviation (SD) was estimated. In order to determine the statistical significance of the differences between boys and girls, Student’s t-test was used (p-value), given that all the variables comply with the assumptions of normality, thus allowing for the use of parametric statistics. Effect size was quantified using Cohen’s d (Rendón-Macías et al., 2021).

In addition, the range was included with a 95% confidence interval (95% CI) to illustrate the minimum and maximum values of each variable, offering a complete view of the dispersion in the total sample. When analysing the data by sex, interquartile range (IQR) was used in order to reduce the influence of outliers that could skew the interpretation of the results. By focusing on the dispersion of the median, the range provides a more robust and representative measure of central variability, particularly useful for comparing distributions between men and women, allowing for a more accurate observation of similarities or differences in the central distribution of data between groups of interest.

3. Results

Table 2. KIDMED index, screen time, health-related quality of life and body image perception of the sample.

	All Participants				Male				Female				Sex Differences
Characteristics	Mean	SD	Range Min/Max	CI 95% Low/Upp	Mean	SD	Range Min/Max	CI 95% Low/Upp	Mean	SD	Range Min/Max	CI 95% Low/Upp	p	d	CI 95% Low/Upp
Sex (M/F, n)	164/141
KIDMED index (a.u)	7.30	2.50	−2/12	7.01/7.58	7.39	2.55	−2/12	7.00/7.78	7.18	2.44	0/12	6.78/7.59	0.474	−0.082	−0.307/0.143
Screen time on weekdays (min/day)	191.00	161.00	0/840	173.00/209.00	185.00	149.00	0/780	162.00/208.00	198.00	173.00	0/840	169.00/226.00	0.501	0.077	−0.148/0.270
Screen time on weekends (min/day)	313.00	191.00	0/840	292.00/335.00	309.00	184.00	0/840	281.00/338.00	318.00	199.00	15/840	285.00/351.00	0.696	0.045	−0.180/0.270
Health-related quality of life (a.u)	3.99	0.83	1/5	3.90/4.08	4.05	0.813	1/5	3.92/4.17	3.82	0.837	2/5	3.78/4.06	0.181	−0.15	−0.379/0.072
Body image perception (a.u)	2.28	1.27	1/5	2.13/2.42	2.27	1.35	1/8	2.06/2.48	2.28	1.17	1/6	2.08/2.47	0.988	0.002	−0.223/0.227

Mean: arithmetic average; SD: standard deviation; Range: difference between minimum and maximum values; CI 95%: confidence interval; IQR: interquartile range; p: p-value; d: effect size (Cohen’s d).

shows the KIDMEX index data, screen time, health-related quality of life and body image perception of the sample, as well as sex differences. No differences were found in any of the variables analysed when divided by sex. Figure 1 illustrates comparative graphs that display the gender differences in the study variables.

Table 3. Comparison of KIDMEX index, screen time, health-related quality of life and body image perception of the sample by sex and age.

	All Participants (n = 305)					Males (n = 164)					Females (n = 141)
	Primary School (n = 167)	Secondary School (n = 138)				Primary School (n = 94)	Secondary School (n = 70)				Primary School (n = 73)	Secondary School (n = 68)
Variable	Mean ± SD	Mean ± SD	p	d	CI 95%	Mean ± SD	Mean ± SD	p	d	CI 95%	Mean ± SD	Mean ± SD	p	d	CI 95%
KIDMED index (a.u)	7.43 ± 2.46	7.14 ± 2.56	0.319	0.115	−0.11/0.34	7.49 ± 2.49	7.26 ± 2.65	0.566	0.091	−0.22/0.40	7.34 ± 2.42	7.01 ± 2.47	0.428	0.134	−0.20/0.46
Screen time on weekdays (min/day)	159.00 ± 148.00	229.00 ± 167.00	<0.001	−0.446	−0.67/−0.22	151.00 ± 134.00	231.00 ± 158.00	<0.001	−0.550	−0.87/0.23	169.00 ± 164.00	228.00 ± 178.00	0.045	−0.341	−0.68/−0.01
Screen time on weekends (min/day)	283.00 ± 181.00	349.00 ± 197.00	0.002	−0.351	−0.58/−0.12	260.00 ± 158.00	375.00 ± 197.00	<0.001	−0.656	−0.98/−0.33	313.00 ± 205.00	323.00 ± 194.00	0.774	−0.049	−0.37/0.29
Health-perception quality of life (a.u)	4.19 ± 0.68	3.75 ± 0.92	<0.001	0.541	0.31/0.78	4.19 ± 0.68	3.86 ± 0.94	0.009	0.419	0.10/0.73	4.18 ± 0.67	3.65 ± 0.90	0.001	−0.666	0.32/1.01
Perception of body image (a.u)	2.09 ± 1.14	2.50 ± 1.38	0.005	−0.326	−0.55/−0.10	1.94 ± 1.15	2.73 ± 1.48	<0.001	−0.608	−0.93/−0.29	2.29 ± 1.09	2.26 ± 1.25	0.908	0.020	−0.32/0.35

Mean: arithmetic average; SD: standard deviation; p: p-value; d: effect size (Cohen’s d).

shows the differences between children in primary school (6th year) and those in secondary school (2nd year) regarding the KIDMED index, screen time, health-related quality of life and body image perception. Differences were found between primary and secondary education students in screen time during the week (p = < 0.001; d = −0.446) and during the weekend (p = 0.002; d = −0.351), perception of health-related quality of life (p = < 0.001; d = 0.541) and perception of body image (p = 0.005; d = −0.326), with higher values for secondary school children. Differences were found in all variables except for the KIDMED. In the case of boys, differences were found in all variables except the KIDMED (screen time during weekdays (p < 0.001; d = −0.550), screen time at weekends (p < 0.001; d = −0.656), health-related quality of life (p = 0.009; d = 0.419) and perception of body image (p < 0.001; d = −0.608)), with higher values in male secondary school students. Meanwhile, differences were found between girls in primary and secondary education in screen time during the week (p = 0.045; d = −0.341) and health-related quality of life (p = 0.001; d = −0.666), with higher values in female secondary school students.

4. Discussion

The purpose of this study is to determine the differences in screen time, level of adherence to the Mediterranean diet, health-related quality of life and perception of body image in children and adolescents according to sex and educational stage. Addressing the reality studied through a multidimensional approach allows for a holistic understanding of how gender and educational stage influence lifestyle habits and personal perceptions, which are determining factors in the comprehensive development and health of young people. The results could help in the design of more effective and personalised educational and public health interventions.

In the case of this study, the data revealed higher levels of screen time, health-related quality of life and perception of body image in secondary school students compared to primary school students. The results show us a high level of screen time that greatly exceeds the WHO recommendations for this population (Asociación Española de Pediatría, 2024). Specifically, there is an increase in screen time, both on weekends and on weekdays, among secondary school students compared to primary school students. These findings are consistent with those of Marks et al. (2015), who observed an increase in screen time and sedentary behaviour in secondary school students compared to primary school students. This growing trend is particularly relevant because excessive screen time significantly contributes to the total amount of sedentary time (Wang et al., 2019). Additionally, studies such as those by Wärnberg et al. (2021), Tambalis et al. (2018) and Ródenas-Munar et al. (2023) show how screen time is associated with low adherence to the Mediterranean diet in both children and adolescents. More screen time can lead to more unhealthy eating habits and lifestyle profiles in schoolchildren (Tambalis et al., 2020). Furthermore, there is considerable evidence that increased screen time is associated with poor quality of life and an unhealthy diet (Stiglic & Viner, 2019), while a correlation has also been found between screen addiction behaviours and decreased PA in young adolescents (Rocka et al., 2022).

Similarly, studies such as the PASOS study (Gómez et al., 2023) confirm that non-compliance with WHO recommendations on screen use in children and adolescents is much higher than stipulated (Gasol Foundation Europa, 2023), with greater adherence to screen use among males and adolescents (Gómez et al., 2023). This is consistent with the results of this study, which show that children and adolescents spend excessive amounts of time in front of screens, with a considerable increase from primary to secondary school. This increase may be due to their growing independence and the intensified use of digital technologies for both educational and recreational activities (J. Qi et al., 2023). Similarly, the use of screens as a socialising and entertainment tool, through social networks and video games, considerably increases screen time (Paulich et al., 2021). The decline in mental health is another negative consequence of this behaviour. It seems to not only depend on the amount of time spent in front of a screen, but also on the purpose for which the screen is used during adolescence (Santos et al., 2023). Individuals with more hours of screen time reported having a poorer HRQOL (Motamed-Gorji et al., 2019).

Another difference in the results in relation to the educational stage is that there is a significant relationship between the levels of study and the perceived HRQOL of the students, which is higher in secondary school students than in primary school students. These results differ from those reported in other studies, such as that of Bar-Haim Erez et al. (2020), in which primary school students report greater satisfaction with their quality of life than secondary school students. Or the study by S. Qi et al. (2020), which stated that as people get older, they face increasingly complex and difficult challenges related to personal and environmental circumstances. Moreover, another study claims that primary school students reported fewer problems in dimensions related to physical functioning, while secondary school students reported more problems related to psychological well-being (Pan et al., 2020).

Nonetheless, the results of this study are in line with those of Santana Vega et al. (2012), who found that secondary school students tend to have clearer personal, academic and professional goals than primary school students and therefore have a higher perception of quality of life. Furthermore, gender differences in subjective well-being are observed in adolescents, but not in children, suggesting that the gender gap in subjective well-being begins at the age of 12 (Esteban-Gonzalo et al., 2020). At the same time, satisfaction with body image correlates with health-related quality of life, whereby secondary school students who are more satisfied with their bodies perceive that they have a better QOL (Ureña et al., 2015).

The transition to early adolescence is a critical stage that presents biological, psychological and social challenges when developmental trajectories may diverge towards healthy adjustments or psychological problems such as anxiety and depression (Rudolph et al., 2001). Most of the health parameters considered are significantly impaired by the experience of a stressful event (Roth et al., 2023). The experience of a stressful event in adolescence has been identified as a predictor of poorer sleep quality, brain changes and modifications in physical health parameters, which may reduce self-perceived health-related quality of life (Roth et al., 2023). Academic stress, due to increased school demands, adaptation to new environments and pressure to meet new challenges and expectations, can negatively affect young people’s emotional well-being (Evans et al., 2018). On the other hand, given that the transition to secondary school involves a significant disruption of friendship groups and an adjustment of social status, the importance of social relationships makes sense. In adolescence, such relationships are crucial, as self-esteem, perceived competence and acceptance depend to a large extent on them (Gillison et al., 2008). In addition, changes in physical activity, in which there is a tendency towards insufficient levels of regular exercise, may contribute to a decrease in physical and emotional well-being (Montero & Juan, 2016; Vega et al., 2010).

Therefore, although studies tell us that most adolescents adapt relatively quickly to their new environment in terms of dimensions of well-being (Gillison et al., 2008; Roth et al., 2023) along the same lines as the results of this study, it is imperative to interpret these findings with caution. Additional research on this phenomenon is needed to more accurately and fully capture the complexity of the multiple factors that influence this dimension.

Measuring this construct in childhood and adolescence can be useful to describe the health of a population and establish comparisons, to identify health problems, to evaluate the scope and impact of interventions and help in their design, or to focus resources according to needs (Jaimes-Valencia et al., 2019).

This study shows higher values of body image perception in secondary education, which translates into a greater perception of overweight or obesity. These data are consistent with those of the study by Abd El Aal Thabet Omar et al. (2021), which show that secondary school boys and girls have a negative attitude towards their body image in relation to their weight. Further studies show that boys tend to underestimate their body weight while girls tend to overestimate it, highlighting the danger of students normalising overweight statuses (Song et al., 2023). Body image, as a social construct widely shared by individuals, is influenced by social aspects and parental influence and can be associated with a decrease in quality of life (Liu et al., 2019).

Whilst body dissatisfaction is common to both age groups, secondary school is a particularly sensitive stage, and there are certain aspects that heighten this feeling. This is in line with our study, in which a higher score in secondary school indicated a greater perception by these students of having a body that is overweight. Studies such as the one by Gonzaga et al. (2023) report a notable increase in body image dissatisfaction among adolescents over the last decade. This dissatisfaction is closely associated with physical activity levels and body composition. Anton-Păduraru et al. (2021) further link obesity in adolescents to low self-esteem, highlighting how weight-related factors significantly impact body image perception and emotional well-being during adolescence. Studies such as those by Sollerhed et al. (2022) relate adolescent well-being to a positive conception of body image, which includes body appearance, body image and high levels of PA. Furthermore, a positive body image has been highlighted as an important component of psychological well-being. Conversely, dissatisfaction with body image has been linked to low self-esteem; depression; and medical, mental and social difficulties (Singh & Manju, 2022). Different factors influence body satisfaction in boys and girls (Gomes et al., 2021). All this is exacerbated by the increase in sedentary time and the use of social networks, which promote unrealistic models. This can lead adolescents to engage in healthier behaviours (balanced diet and exercise) and not-so-healthy behaviours (the use of harmful substances to lose weight or dieting without professional supervision) in order to feel better about their image.

Physical change is experienced when a child loses his or her childish body during puberty, which increases their concern about their body image (Enríquez Peralta & Quintana Salinas, 2016). This is why adolescence is a critical period for this aspect. Most adolescents consider the importance of physical appearance over interest in the opposite sex. In the representation of the male body, models with an athletic build are prioritised, and in the case of females, slimmer bodies are prioritised (Pérez-Mármol et al., 2023). Salazar Mora (2008) is still up to date when he states that in the current era, there is a cult of youth with slim body aesthetic patterns and society is characterised by the cult of the body, which is a highly significant pressure for the adolescent group (Salazar Mora, 2008).

Furthermore, different social networks and media have an impact on young people’s perception of their body image, setting unrealistic standards of beauty (Fardouly & Vartanian, 2016). This biased representation can lead adolescents to internalise these ideals and perceive their own weights as inadequate or overweight, even when their weight is normal. In turn, in adolescence, young people are forging their body image through experiences, personal performances, the consequences of their own actions and the approval and disapproval of others. The peer group usually responds to official social models, so they are likely to suffer from uncertainty and dissatisfaction with their own bodies (Salazar Mora, 2008).

Finally, no significant differences were found in relation to adherence to the Mediterranean diet between primary and secondary school students, both of whom showed a medium level of adherence. This may be due to the fact that the eating habits of children tend to be established at an early age. Therefore, primary school children who already have a diet that follows the principles of the Mediterranean diet are likely to continue with this trend in secondary school (Chong, 2022). Furthermore, family influence affects adherence; thus, the same habits will be followed within the same family regardless of educational stage (Buja et al., 2020; Franic et al., 2022).

In terms of the analysis by sex, this study did not find significant differences in any of the variables. These results differ from studies such as that of Arrayás Grajera et al. (2018), which states that, although boys and girls are similar in regards to their desire to lose weight, girls feel more dissatisfied with their body image than boys. The study by Tripathi & Mishra (2019) found significant differences in the levels of use of screen devices according to sex. Additionally, when considering health-related quality of life, there are studies that state that girls and female adolescents experience a lower health-related quality of life in relation to their health than boys, due in part to the earlier development of girls and sex differences in pubertal development (Svedberg et al., 2013).

However, other studies, such as the one by Pearson et al. (2009), support our results, arguing that, in relation to adherence to the Mediterranean diet, no significant differences were found according to sex in adolescence. In the same way, another study highlights that most research analysing the degree of adherence to the Mediterranean diet among Spanish adolescents and adolescents from different countries has not found significant differences between sexes either (Tapia-Serrano et al., 2021). Regarding other variables, there are studies such as the one by Maljur et al. (2022) that have observed no significant differences in screen time between students of both sexes. Another example is the study by Gómez-Mármol et al. (2013), which states that no significant differences were found in body image dissatisfaction between boys and girls. In terms of quality of life, sex differences, usually favouring boys, can be reduced or even reversed when girls are physically active. This highlights the importance of promoting physical activity, especially among girls, to improve their quality of life (Sánchez-López et al., 2009).

The results of our study, which show the inexistence of significant differences between boys and girls in eating habits, self-perception of body image, health-related quality of life and screen time, could be explained by their current access to resources in this context and the convergence in the processes of socialisation. The widespread availability and use of mobile devices and digital platforms have homogenised consumption patterns, with both genders accessing a wide variety of content in a similar way. This suggests that, while there may be significant differences in specific activities (Sevil Serrano et al., 2018), overall screen use tends to converge between the two genders. Public health interventions and educational policies aimed at promoting healthy lifestyles have contributed to a decrease in traditional disparities, which favours uniform behaviours and perceptions regarding food and body image (Colás & Castro, 2011; Carballo et al., 2023; García Cabrera et al., 2015; Mastorci et al., 2020). Moreover, the current social context, characterised by a greater equality in opportunities and a homogeneous dissemination of health information, means that both boys and girls can develop a balanced perception of their well-being and quality of life (Heredia-Bolaños & Grisales-Romero, 2019).

The study underlines the importance of implementing integrated strategies in both public policies and school programmes. In the former, it is necessary to develop regulatory frameworks that facilitate the transition in educational stages, promoting healthy lifestyles and considering that the change in school environment is a critical moment for the adoption of behaviours related to well-being. In the same way, schools are positioned as a strategic environment for the design of curricular interventions aimed at the prevention and improvement of students’ comprehensive health, allowing for early detection. The synergy of these two spheres can contribute to increasing the effectiveness of interventions during this formative stage.

Despite these promising insights, the study has several limitations that should be considered. Firstly, being a study with a small sample, the representativeness of the results is limited, requiring more studies of this type within the Galician community. Likewise, no anthropometric measurements were taken to verify and contrast the body image self-concept of the participating children and adolescents with objective data. Secondly, as the data were collected via a self-administered questionnaire, the responses may have been inaccurate. Although the study was supervised by researchers, the attitude and degree of cooperation of the participants could have influenced the accuracy of the responses.

To enrich future research and overcome some of the limitations of the present study, we suggest the use of objective measures such as accelerometers to assess physical activity and nutritional biomarkers to contrast and complement the information obtained through self-reports. These objective tools would not only provide methodological rigour but would also facilitate the comparison of results between studies and different contexts, offering a more accurate view of behaviours and health status in the child and adolescent population. In addition, for future studies, it is recommended that additional statistical analyses, such as a multivariate analysis of variance or an analysis of covariance, are conducted to control for other confounding variables that may influence the results.

Furthermore, in terms of relevant factors, there are no known studies that jointly analyse adherence to the Mediterranean diet, screen time, the health-related quality of life and body image of Galician children and adolescents. Taking into account that the Galician community is at the bottom of the quality-of-life index in Spain (UNICEF, 2018), this type of study is considered to be of special relevance. Furthermore, specifically, in the municipality of Oleiros, which has the highest per capita income in Galicia and to which this sample belongs, there are no studies that analyse this subject.

Prioritising health-related quality of life in children and young people is important as they represent the future of society. Therefore, adopting a multidimensional perspective that encompasses physical, mental and social well-being lays the foundations for sustainable development (Ródenas-Munar et al., 2023).

Screen time is very high in both children and adolescents due, among other reasons, to the digital literacy that surrounds the educational environment. Therefore, it might be interesting to develop future lines of research that focus on studying other opportunities for engagement and learning to move towards a balance in this literacy, which would allow for a reduction in sedentary and screen time. However, although there are plenty of studies on screen time, it would be interesting to investigate the nature of the content offered on each device, as well as how children and teenagers interact with it.

Similarly, the issue of children’s physical self-concept from the perspective of their parents is essential to address, investigating which role models parents’ perceive as ideal and healthy for their children and how they perceive their children’s body image. It is essential to further explore the role of the family and socio-economic environment in shaping health habits. The influence of the context in which children and adolescents live can largely determine their eating practices, use of electronic devices and perception of their own body image.

Investigating these variables from an integrated and multidimensional perspective would allow for the identification of risk and protective factors, contributing to the development of more effective and personalised intervention strategies in the field of both public policies and school programmes.

5. Conclusions

The results of this study reflects several key dynamics related to health and lifestyle habits in children and adolescents. The decrease in adherence to the Mediterranean diet highlights the need to educate children about the importance of a balanced diet from an early age, also taking into account the affordability of healthy foods. The analysed sample showed no significant differences in the KIDMED index based on educational level or sex, which reflects the homogeneity in the eating patterns of the studied population.

On the other hand, excessive screen time represents another relevant factor identified in this study, which increases particularly during secondary education. This emphasizes the need to analyse the impact of digital device usage, both in educational settings and during leisure time, given its association with various negative consequences for physical, psychological and social health. In this context, it is essential to implement effective strategies aimed at mitigating this behaviour and promoting healthy lifestyle habits among young people.

Furthermore, the study reveals that a group of secondary school students perceive themselves as overweight, likely influenced by factors related to puberty and social environments. These variables make body image a defining aspect at this stage, with a significant impact on student development. This finding underscores the importance of educational interventions focused on fostering healthy habits and reducing gender-based stereotypes.

Finally, the study shows a higher level of health-related quality of life (HRQOL) in secondary school students compared to primary school students, suggesting that increased autonomy and adaptation during secondary education may positively influence their physical and emotional well-being.

The variables previously mentioned are closely linked to the health-related quality of life perceived by children and adolescents. The perception of their own body in comparison with their peers and society; the amount of time spent using screens, which restricts them from carrying out other activities that are more beneficial for their physical, psychological and social health; and the type of diet, which directly influences their health and physical constitution, are all aspects that must be studied. This analysis is essential to ensure proper development in childhood and adolescence and to train future adults to understand the importance of maintaining healthy habits throughout their lives.

Contrary to previous research that has generally addressed these variables in an isolated manner or in heterogeneous samples at a national or international level, our study is distinguished by a multidimensional approach and focuses on a specific and little explored environment, which allows us to precisely identify the dynamics of this context. Moreover, the significant homogeneity found between genders in all the domains studied suggests that contextual factors specific to the Oleiros environment could be modulating the traditionally expected differences, which opens up new lines of research on the levelling role of educational and social environments. This approach offers novel evidence for the design of interventions and public policies, expanding existing theoretical knowledge and providing a solid basis for the development of educational and health strategies that are adapted to the specific needs of children at this formative stage.