Table 1.
Characteristics of the included studies
| Author, publication year | Country | Study design | Total subjects | Inclusion criteria | Characteristics of participants | MD adherence scoring system ‡ |
MD adherence dimensions | HRQoL measure ‡ | HRQoL dimensions | Adjusted variables | Funding | |||
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Gender and age | BMI (kg/m2) | Physical activity | Weight † | |||||||||||
| Costarelli et al., 2012 [14] | Greece | Cross-sectional | 359 (13–16 years old) | Participants signed consent forms and received a full verbal and written explanation of the purpose of the study and its anonymous nature | 46.2% boys Median age: 13.1 years (IQR: 0.5) | 19.9 (SD, 3.2) | NR | Normal weight: 80.6% Overweight: 15.6% Obesity: 2.5% | KIDMED index | 16 dichotomous items (yes/no): 12 items: behaviors consistent with the Mediterranean diet 4 items: behaviors inconsistent with the Mediterranean diet | KIDSCREEN-27 | 5 Dimensions: 1. Physical well-being (5 items) 2. Psychological well-being (7 items) 3. Parent relations and autonomy (7 items) 4. Social support and peers (4 items) 5. School environment (4 items) | Number of meals, number of meals (with family), BMI, obesity, father’s education level, mother’s education level, gender | Institutional support. Human Ecology Laboratory, Department of Home Economics and Ecology, Harokopio University of Athens |
| Muros et al., 2017 [15] | Spain | Cross-sectional | 456 (11–14 years old) | Twenty-four adolescents were excluded for failing to complete some testing element or failing to attend class on their testing day | 48.5% boys Mean age: 12.57 years (SD, 1.17) | 19.75 (SD, 3.85) | PAQ-C score: 2.92 (SD, 0.64) | Normal weight: 75.7% Overweight: 16.7% Obesity: 5.5% | KIDMED index | 16 dichotomous items (yes/no): 12 items: behaviors consistent with the Mediterranean diet 4 items: behaviors inconsistent with the Mediterranean diet | KIDSCREEN-27 | 5 Dimensions: 1. Physical well-being (5 items) 2. Psychological well-being (7 items) 3. Parent relations and autonomy (7 items) 4. Social support and peers (4 items) 5. School environment (4 items) | BMI, physical activity | NR |
| Zervaki et al., 2017 [16] | Greece | Cross-sectional | 400 (14–17 years old) | Participants that signed consent forms received a full verbal and written explanation of the purpose of the study and its anonymous nature | 49.5% boys Median age: 15.8 years (IQR: 1.03) | 21.7 (SD, 3.1) | NR | Normal weight: 75.0 Overweight: 21.5 Obesity: 3.5% | KIDMED index | 16 dichotomous items (yes/no): 12 items: behaviors consistent with the Mediterranean diet 4 items: behaviors inconsistent with the Mediterranean diet | KIDSCREEN-27 | 5 Dimensions: 1. Physical well-being (5 items) 2. Psychological well-being (7 items) 3. Parent relations and autonomy (7 items) 4. Social support and peers (4 items) 5. School environment (4 items) | Number of meals, number of meals (with family), age, obesity, father’s education level, mother’s education level, BMI | NR |
| Evaristo et al., 2018 [17] | Portugal | Cross-Sectional | 946 (12–18 years old) | All students that agreed to participate in the study | 53.3% boys Mean age: 14.5 years (SD, 1.8) | 21.1 (SD, 3.8) | NR | NR | KIDMED index | 16 dichotomous items (yes/no): 12 items: behaviors consistent with the Mediterranean diet 4 items: behaviors inconsistent with the Mediterranean diet | KIDSCREEN-10 | It contains 10 items regarding family life, peers, and school life | Physical fitness, age, sex, pubertal stage (Tanners A and B), socioeconomic status, sleep duration, BMI | Portuguese Foundation for Science and Technology (FCT) grants |
| Esteban-Gonzalo et al., 2019* [18] | Spain | Cross-Sectional |
(a) 536 children at primary school (6–7 and 9–10 years old) (b) 987 adolescents at secondary school (12–13 and 15–16 years old) |
(i) To study in the first/fourth grades (6–7 and 9–10 years old, respectively) for children and seventh/tenth grades (12–13 and 15–16 years old, respectively) for adolescents at baseline and (ii) to not have physical disability or health problems, which may limit the levels of physical activity | Primary school: 49.8% boys Mean age: 8 years (SD, 1.5) Secondary school: 51.3% boys Mean age: 8.2 years (SD, 1.5) | NR | NR | Overweight and obesity Primary school: Boys: 35.6% Girls: 36.9% Secondary school: Boys: 39.0% Girls: 21.9% | KIDMED index | 16 dichotomous items (yes/no): 12 items: behaviors consistent with the Mediterranean diet 4 items: behaviors inconsistent with the Mediterranean diet | KIDSCREEN-10 | It contains 10 items regarding family life, peers, and school life | Age, socio-economic status, prevalence of overweight, and obesity | DEP 2010- 21,662-C04-00 grant from the National Plan for Research, Development and Innovation (R + D + i) |
| Ferrer-Cascales et al., 2019 [19] | Spain | Cross-Sectional | 527 (12–17 years old) | NR | 45.5% boys Mean age: 14.43 years (SD, 1.52) | NR | NR | NR | KIDMED index | 16 dichotomous items (yes/no): 12 items: behaviors consistent with the Mediterranean diet 4 items: behaviors inconsistent with the Mediterranean diet | KIDSCREEN-52 | 10 Subscales: 1. Physical Well-Being 2. Psychological Well-Being 3. Mood and Emotions 4. Self-Perception 5. Autonomy 6. Parent Relations and Home Life 7. Financial Resources 8. Social Support and Peers 9. School Environment 10. Social Acceptance | NR | Self-funded |
| Delgado-Floody et al., 2020 [20] | Chile | Cross-Sectional | 619 (10–13 years old) | (i) To be a student of a public school in the La Araucanía region, (ii) to have a regular physical education class and (iii) to be aged between 10 and 13 years. The exclusion criteria were as follows; (i) having musculoskeletal disorders or (ii) any other known medical condition, which may alter the participant’s health and PA levels; and (iii) to have scholars commitment that they could be interrupted by the study measurements | 55.9% boys Mean age: 11.72 years (SD: 1.07) | 21.57 (SD, 4.68) | NR | Normal weight: 50.4% Overweight: 25.2% Obesity: 24.4% | Krece Plus test | The questionnaire contains 15 items, where the maximum possible score was + 11 and the minimum was − 5. Each item has a score of + 1 or − 1, depending on whether it approximates the ideal of the MD. The total points are accounted and, according to the score, the nutritional status is classified as follows: (1) “low” nutritional level, ≤ 5; (2) “moderate” nutritional level, 6–8; and (3) “high” nutritional level, ≥ 9 | KIDSCREEN-10 | It contains 10 items regarding family life, peers, and school life | Age, sex | Research Project R01/18 from the Universidad de Los Lagos and by private fundings |
| Rodriguez-Rosado et al., 2020 [21] | Spain | Cross-Sectional | 114 (8–10 years old) | Parents/tutors of participants signed informed consent | Male: 9.53 years (SD, 0.64) Female: 9.54 years (SD, 0.6) | Male: 18.8 (SD, 4.52) Female:18.4 (SD, 4.19) | PAQ-A: Male: 3.82(0.76) Female:3.56 (0.83) | NR | KIDMED index | 16 dichotomous items (yes/no): 12 items: behaviors consistent with the Mediterranean diet 4 items: behaviors inconsistent with the Mediterranean diet | KIDSCREEN-27 | 5 Dimensions: 1. Physical well-being 2. Psychological well-being 3. Autonomy and relationship with parents 4. Social relationships and Peer pressure 5. School environment | NR | NR |
| Caamaño-Navarrete et al., 2021 [22] | Chile | Cross-Sectional | 634 (11–13 years old) | Chilean schoolchildren aged between 11 and 13, without musculoskeletal disorders or any other known medical conditions that may alter the participants’ health and PA levels | 55.5% boys Mean age: 11.95 years (SD, 0.85) | 21.6 (SD, 4.58) | 2.64 h/week (1.42) | NR | KIDMED index** | Each item has a score of + 1 or – 1, depending on whether it approximates the ideal of the MD. The sum of all values from the administered test is categorized into three different levels: (1) > 8, optimal MD; (2) 4–7, improvement needed to adjust intake to Mediterranean patterns; and (3) ≤ 3, very low diet quality | KIDSCREEN-10 | It contains 10 items regarding family life, peers, and school life | NR | NR |
| Mitri et al., 2021 [23] | Lebanon | Cross-Sectional | 798 (11–18 years old) | Students suffering from physical disabilities or who were absent on the days of the data collection were not invited to participate in the study | 52.9% boys Mean age: 15 years (SD, 2.07) | NR | PAQ C/A: 2.46 (0.75) | Normal weight: 55.4% Overweight: 20.2% Obesity: 19.3% | KIDMED index | 16 dichotomous items (yes/no): 12 items: behaviors consistent with the Mediterranean diet 4 items: behaviors inconsistent with the Mediterranean diet | KIDSCREEN-27 | 5 Dimensions: 1. Physical well-being 2. Psychological well-being 3. Autonomy and relationship with parents 4. Social relationships and Peer pressure 5. School environment | School type, grade, age, skipping meals, father's education level, number of meals, number of meals with family, and physical activity | Self-funded |
| Mozzillo et al., 2021 [24] | Italy | Cross-sectional | 420 (13–17 years old) | Age 13.0–17.0 years; Caucasian ethnicity; overweight or obesity; first visit at the outpatient clinic. The exclusion criteria were secondary causes of obesity (genetic, endocrine, or iatrogenic forms) and other chronic diseases or mental illnesses | 44.5% boys Median age: 14.0 years (IQR: 13.2; 15.0) | 31.2 (IQR: 28.7; 34.2) | 0 h/week (0–3) | 82.3 (IQR: 73.6; 93.2) | KIDMED index | 16 dichotomous items (yes/no): 12 items: behaviors consistent with the Mediterranean diet 4 items: behaviors inconsistent with the Mediterranean diet | Pediatric Quality of Life Inventory (PedsQL) |
4 Dimensions: 1. Physical functioning 2. Emotional functioning 3. Social functioning 4. School functioning |
BMI, father’s education level (year), mother’s education level (year), exercise (hours/week) | Self-funded |
Data are presented as mean (SD) or median (IQR)
*Originally a longitudinal study, it was considered the baseline cross-sectional cohort
**The original article states that the Kreece Plus scale was used, but the KIDMED scale is cited and used
†Obesity classification (%) IOTF cutoff points, except in Delgado et al. and Mitri et al. classified with CDC criteria
‡ Self-reported score
BMI (body mass index), MD (Mediterranean diet), HRQoL (Health-Related Quality of Life), KIDMED (Mediterranean Diet Quality Index), KIDSCREEN (KIDSCREEN test), PedsQL (Pediatric Quality of Life Inventory), Krece Plus (Krece PLus test), SD (standard deviation), IQR (interquartile range), NR (not reported), PAQ-C (Physical Activity Questionnaire for Older Children, a five-point scale), PAQ-A (Physical Activity Questionnaire for Adolescents, a five-point scale), PAQ C/A (Physical Activity Questionnaires for Children and Adolescents, a five-point scale)