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Table 1 Characteristics of the included studies

From: Adherence to Mediterranean diet associated with health-related quality of life in children and adolescents: a systematic review

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
  1. Data are presented as mean (SD) or median (IQR)
  2. *Originally a longitudinal study, it was considered the baseline cross-sectional cohort
  3. **The original article states that the Kreece Plus scale was used, but the KIDMED scale is cited and used
  4. Obesity classification (%) IOTF cutoff points, except in Delgado et al. and Mitri et al. classified with CDC criteria
  5. Self-reported score
  6. 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)