Exploring the Associations Between Systematic Engagement in Physical Activity, Dietary Habits and Body Composition in a Sample of Greek Adolescents

Abstract

(1) Background: Adolescence is a critical period in human life, particularly in relation to the development of a healthy lifestyle. Physical activity, body composition and adherence to healthy dietary patterns are key indicators for preventing adolescent overweight and obesity. The aim of this study is to explore the associations between systematic engagement in physical activity, dietary habits and body composition in a sample of Greek adolescents. (2) Methods: In this cross-sectional study, 292 adolescent volunteers, aged 12 to 18 years, from high schools in the Attica region (169 boys [57.9%] and 123 girls [42.1%]) participated. The participants’ socio-demographic characteristics and physical activity levels were assessed through self-reported questionnaires. Their dietary habits were evaluated using the KIDMED questionnaire, and their body composition was determined via bioelectrical impedance analysis. (3) Results: The majority of the students (80.8%) was involved in organized exercise, either as part of a team or in individual sports activities. Physically active participants had significantly improved body composition profiles compared to their non-active peers. No significant differences were observed in the KIDMED scores between boys and girls. However, significantly higher KIDMED scores were found in the group of physically active adolescents compared to the non-active group, with this difference being more pronounced among boys. (4) Conclusions: Engagement in organized physical activity is associated with healthier dietary choices, contributing to a more favorable overall lifestyle profile among adolescents.

1. Introduction

Adolescence is a critical growth period marked by major physical and metabolic changes that impact future health [1]. The World Health Organization (WHO) defines adolescence as the period between 10 and 19 years, while youth refers to individuals aged 15 to 24 [2]. The recent Lancet Commission on Adolescent Health and Well-Being further divides this period into early adolescence (10–14 years) and late adolescence (15–19 years) [3]. While not as vulnerable as infants or children, adolescents remain a susceptible population due to heightened growth needs, poor dietary choices and high-risk behaviors [4]. During this time, adolescents face nutritional challenges including undernutrition, obesity and nutrient deficiencies. Importantly, eating habits and overall lifestyle characteristics established during adolescence, including physical activity and exercise, often persist throughout life [5,6,7].

The prevalence of childhood and adolescent obesity has dramatically increased in recent years, becoming a global public health concern [8]. According to the U.S. Centers for Disease Control and Prevention (CDC), the prevalence of childhood obesity in the United States during 2017–2020 was 19.7%, affecting approximately 14.7 million children and adolescents. Similarly, in the European region of the WHO, the prevalence of overweight and obesity among children and adolescents varies between 3% and over 10%, depending on the country [9]. Numerous studies have highlighted the growing problem of childhood obesity in Greece [10,11,12,13].

Obesity is a major risk factor for non-communicable diseases in adulthood, such as atherosclerosis, metabolic syndrome and type 2 diabetes [2,14]. Childhood obesity has been linked to a variety of health issues, including early puberty [15], early bone growth [16], sleep disorders [17,18], elevated insulin levels [19], psychological concerns due to poor self-image and eating disorders [20,21], and cardiovascular risk factors such as hypertension and hypercholesterolemia [17,22].

While many factors contribute to the development of obesity, a definitive explanation remains elusive. It is well known that obesity results from excessive fat accumulation, driven by a positive energy balance—where dietary energy intake exceeds energy expenditure [23]. Key factors associated with the development of obesity include physical inactivity, poor nutrition, alcohol consumption, and smoking [24,25]. The WHO reports that 80% of adolescents fail to meet the recommended exercise levels [26,27,28], which are set at 60 min of moderate- to vigorous-intensity exercise per day for children aged 5–17.

Physical activity provides several physical, mental and cognitive benefits to young people. Both aerobic and resistance exercise, in combination with nutritional programs, have been reported to improve body composition and metabolic parameters, whereas physical inactivity is associated with several detrimental health outcomes, being a significant risk factor for various non-communicable diseases (NCD’s) [29,30,31,32,33,34,35,36,37,38]. A recent systematic review and meta-analysis comparing the body composition of active and sedentary adolescents revealed that those who engage in regular physical activity exhibit better physical fitness, improved maximum oxygen uptake, greater strength and lower levels of fat mass than their sedentary counterparts [39]. There is a scarcity of data on the association of systematic engagement in physical activity, body composition and dietary habits among Greek adolescents. Findings from the Greek study EYZHN indicate that children and adolescents with excess body and abdominal fat demonstrate poor physical fitness [40], which is associated with increased cardiometabolic risk factors [41,42]. The EYZHN study also showed that children with good physical fitness tend to have healthier nutritional habits, a conclusion supported by numerous other studies [43,44,45,46].

The Mediterranean Diet has been extensively studied as a dietary pattern linked to improved health outcomes [47]. The Seven Countries Study was the first epidemiological investigation to report the benefits of this traditional diet [48]. Since then, numerous studies have confirmed various health advantages associated with the Mediterranean Diet [49,50]. This dietary pattern is characterized by high consumption of fruits, vegetables, legumes, whole grains, nuts and olive oil; low consumption of animal products and processed meats; and moderate to high consumption of fish, eggs, and white meat [47,51].

Adherence to the Mediterranean Diet among adolescents can be accurately estimated using the KIDMED score, developed by Serra Majem et al. in 2004 [47]. However, in recent decades, adherence to the Mediterranean Diet has been low to moderate, as there has been a shift toward a Western-style diet among adolescents [52,53,54]. This trend may be influenced by various cultural, socio-economic and geographical factors [55,56]. Additionally, adherence to the Mediterranean Diet may be impacted by other behaviors, such as engagement in regular physical activity, though this potential association has not been thoroughly explored in adolescent populations.

The primary objective of this study was to assess whether the dietary habits of Greek adolescents, particularly their adherence to the Mediterranean Diet, are associated with their participation in organized sports. A secondary objective was to compare body composition indices between adolescents who engage in regular sports activities, in specific sport activities and in no sports activities.

2. Materials and Methods

2.1. Study Design

This cross-sectional study investigated the dietary habits and body composition of adolescents, while considering their systematic engagement in sports. The study received approval from the Bioethics Committee of the University of West Attica (Reference number: 112168/14-12-2021).

2.2. Study Procedure

After receiving the necessary entry licenses from the Ministry of Education, the research team contacted 20 school principals to explain the survey’s purpose and request consensus for participation. Schools from all regions of the Attica basin (northern, southern, eastern, and western) were approached to ensure a representative population sample for Attica.

Fourteen schools (13 public and 1 private) agreed to participate in the study. Approval was then granted to briefly discuss the study’s goals with nearly every class in each school for 5 to 7 min, without disrupting the academic program. Five hundred (500) students were informed about the study. Parental consent forms were distributed to these students, who were asked to return them within two weeks. Students who returned signed parental and personal consent forms completed the study’s questionnaires and underwent body composition assessments during a school hour. Figure 1 shows the recruitment and participation process. Data collection occurred between March 2022 and the end of 2023.

2.3. Study Participants

In total, 292 adolescents returned signed parental consent forms and confirmed their own consent to participate. To be eligible for inclusion, participants needed to be aged 12 to 18 years, able to understand Greek, and provide a health certificate from a pediatrician. Adolescents with chronic diseases, those under pharmaceutical treatment, and those who had recently contracted COVID-19 or other viral infections were excluded.

2.4. Exercise Engagement and Physical Activity Assessment

Physical activity levels and engagement in daily exercise were assessed using a validated physical activity questionnaire. This questionnaire included questions about participants’ daily routines and their involvement in organized sports activities, such as team sports, gym activities or both [57]. The questionnaires used in the current study are included in the Supplementary Material (S1 and S2). Based on their responses, participants were categorized into those engaged in team sports, indoor gym activities or both and those not following any organized exercise regime. Organized exercise activities referred to weekly training schemes under the supervision of certified trainers which were not part of school activities and took place in sports clubs. The non-exercise group included adolescents who did not participate in organized team sport or indoor activities. The team sports group involved adolescents who were engaged in weekly training programs of team sports such as soccer, basketball, volleyball, etc. The indoor gym sport group included participants who were engaged in training programs of individual sports such as gymnastics, martial arts, weight lifting, etc. Finally the team and gym group involved participants who were engaged in both team and indoor gym activities.

The participants were also categorized according to their adherence to the WHO recommendations for physical activity among adolescents. The WHO recommends at least 60 min of moderate to vigorous physical activity (MVPA) per day [58]. MVPA was assessed by using the validated physical activity questionnaire, adding the daily time spent training in minutes for each active adolescent, evaluating the total weekly time in minutes and, finally, adding their total weekly training time in minutes for all exercise categories (team, gym, team and gym), as well as the recreational exercise time (exercise performed in their spare time).

2.5. Nutritional Assessment

Dietary habits were assessed using the KIDMED questionnaire [47]. The KIDMED questionnaire consists of 16 questions, 12 of which are positively scored (concerning the frequency of consuming vegetables, fruits, fish, legumes, olive oil, nuts, cereals, rice, pasta and yogurt), and 4 of which are negatively scored (concerning the frequency of consuming fast food, sweets and pastries and skipping breakfast). Questions that are positively related to the Mediterranean Diet are scored with +1 point, while items that are negatively related to the diet are scored with −1 point. The sum of these values provides a total KIDMED score, which measures adherence to the Mediterranean Diet. Based on their total score, participants were classified as having a high-quality diet (>8), medium-quality diet (4–7) or low-quality diet (<3).

2.6. Body Composition Assessment

Standing height was measured without shoes to the nearest 0.1 cm using a portable stadiometer (Seca 213, Seca, Hamburg, Germany). Body weight and composition, in terms of fat-free mass (FFM), fat mass (FM) and Basal Metabolic Rate (BMR), were assessed with a portable body composition analyzer utilizing bioelectrical impedance (BIA) (InBody H20B Body Fat Analyzer, Seoul, Republic of Korea). The software used for the analyses was the website myinbody.com (http://myinbody.com/qrintro.htm?CID=G52017237, accessed on 12 March 2024), which allows users to check and manage their InBody test results. Body Mass Index (BMI) was calculated using the formula weight (kg)/height² (m²). Based on the WHO growth reference charts for children aged 5–19 years, participants were classified as underweight (<5th percentile), normal weight (5th to 85th percentile), overweight (85th to 95th percentile) or obese (>95th percentile) [59].

2.7. Statistical Analysis

We performed statistical analyses on the full dataset and on stratified samples, specifically examining differences between early (12–15 years) and late (16–18 years) adolescents, as well as their subgroups defined by gender, sports engagement, and exercise modality. The normality of continuous variables was tested using the Kolmogorov–Smirnov test. Variables following a normal distribution are presented as the mean ± SD, while non-normally distributed variables are expressed as the median [25th–75th percentiles]. Categorical variables are reported as frequencies and percentages (%). Differences in anthropometric characteristics and KIDMED scores between genders and exercise groups were analyzed using the non-parametric Mann–Whitney U test for two independent samples and the Kruskal–Wallis test for k-independent samples with a post hoc Dunn’s test for pairwise comparisons. Comparisons regarding adherence to specific dietary behaviors between genders and exercise groups were performed using the chi-squared (χ²) test. All p-values were two-tailed, with statistical significance set at p < 0.05. Data analysis was conducted using the Statistical Package for Social Sciences (SPSS Inc., Chicago, IL, USA) version 25.0.

3. Results

3.1. Population Characteristics

This cross-sectional study included 292 adolescents (42.1% female), aged 12–18 years, recruited from various public and private schools across the Attica region. Most of the participants were from the final three classes of high school (Lyceum, Classes A, B and C). There was no significant difference in the percentage of male and female participants across classes. The median age of the sample was 15.0 years (14.0–16.0), and the majority of participants were of Greek nationality (94.2%), followed by Albanian (2.7%), Egyptian (0.7%) and other less often reported nationalities (2.4%).

Table 1. Anthropometric variables and KIDMED scores by gender.

Variables	Total Population			Early Adolescents		Late Adolescents
	All (N = 292)	Boys (N = 169)	Girls (N = 123)	All (N = 81)	Boys (N = 45)	Girls (N = 36)	All (N = 211)	Boys (N = 124)	Girls (N = 87)
Age (years)	15.0 (14.0–16.0)	16.0 (14.0–16.0)	15.0 (14.0–16.0)	13.0 (12.0–14.0)	13.0 (13.0–14.0) #	13.0 (12.0–14.0) $	16.0 (15.0–17.0)	16.0 (15.0–17.00) #	16.0 (15.0–17.0) $
Height (m)	1.70 (1.62–1.76)	1.76 (1.70–1.79) *	1.62 (1.58–1.67) *	1.64 (1.58–1.75)	1.72 (1.61–1.77) *#	1.61 (1.56–1.64) *	1.71 (1.64–1.77)	1.76 (1.72–1.80) *#	1.63 (1.59–1.67) *
Weight (kg)	61.8 (53.2–69.7)	66.6 (58.5–73.3) *	54.8 (50.5–62.8) *	55.8 (48.2–63.1)	58.3 (49.4–65.5) *#	51.6 (45.9–60.9) *$	64.6 (55.3–72.3)	68.0 (62.0–76.2) *#	55.3 (52.1–64.8) *$
BMI (kg/m2)	20.9 (19.3–23.2)	21.1 (19.3–23.5)	20.8 (19.3–22.7)	19.6 (17.9–20.9)	19.6 (17.7–20.8) #	19.8 (18.0–21.7) $	21.4 (20.0–23.6)	21.9 (20.3–24.1) #	21.1 (19.5–23.2) $
Body weight categories
Underweight (%)	4.5	3.0	6.5	2.0	2.2	2.8	5.2	3.2	8.0
Normal weight (%)	75.3	72.8	78.9	79.0	80.0	77.8	73.9	70.2	79.3
Overweight (%)	15.4	17.8	12.2	14.8	11.1	19.4	15.6	20.2	9.2
Obese (%)	4.8	6.5	2.4	3.7	6.7	0	5.2	6.5	3.4
FFM (kg)	26.9 (22.2–32.8)	31.8 (27.7–35.5) *	22.2 (20.4–24.4) *	24.6 (20.7–30.3)	27.5 (22.5–32.5) *#	22.3 (20.3–24.3) *	29.3 (22.5–33.4)	32.8 (29.9–36.3) *#	22.2 (20.4–24.8) *
FM (kg)	11.0 (6.9–15.8)	8.6 (5.8–13.1) *	13.8 (9.7–18.0) *	8.3 (4.5–14.5)	5.3 (4.0–9.5) *#	11.1 (8.3–16.0) *$	11.9 (7.9–16.2)	10.1 (6.8–13.7) *#	14.6 (10.9–18.6) *$
FM (%)	17.9 (11.8–25.4)	13.7 (9.5–18.3) *	24.7 (19.3–29.6) *	16.7 (8.0–25.6)	9.6 (6.6–17.5) *#	22.9 (16.5–26.7) *	18.2 (12.6–25.3)	14.5 (11.2–18.5) *#	25.2 (20.5–30.6) *
BMR (kcal/day)	1422.0 (1252.0–1630.0)	1595.0 (1450.0–1722.0) *	1254.5 (1186.2–1342.7) *	1340.0 (1206.0–1543.0)	1439.0 (1259.02–1620.7) *#	1260.0 (1181.0–1327.0) *	1506.0 (1267.0–1655.0)	1623.0 (1525.0–1751.0) *#	1253.0 (1187.0–1361.0) *
KIDMED score	6.0 (4.0–7.0)	6.0 (4.0–8.0)	6.0 (4.0–7.0)	6.0 (4.0–8.0)	6.0 (4.0–8.0)	7.0 (5.0–8.0)	6.0 (4.0–7.0)	6.0 (4.0–7.0)	6.0 (4.0–7.00)

Results are presented as medians (25th–75th Percentile). * p ≤ 0.05 for between-gender comparisons. # p ≤ 0.05 for comparisons between early adolescent boys and late adolescent boys. $ p ≤ 0.05 for comparisons between early adolescent girls and late adolescent girls. BMI: Body Mass Index. FFM: fat-free mass. FM: fat mass. BMR: Basal Metabolic Rate.

presents the basic anthropometric and body composition characteristics by gender. As expected, boys were taller and heavier and had higher values for FFM and BMR compared to girls. Conversely, girls had higher BF and BF percentages than boys.

3.2. Systematic Engagement in Sports

The majority of the participants (80.8%) were involved in organized exercise, either as part of a team or by participating in individual sports activities (

Table 2. Distribution of participants by engagement in sports and gender (N (%)).

Exercise	All Participants			Early Adolescents			Late Adolescents
Type of Exercise	All (N = 286)	Boys (N =167)	Girls (N = 119)	All (N =78)	Boys (N = 44)	Girls (N =34)	All (N = 208)	Boys (N = 123)	Girls (N = 85)	P for Gender
No Exercise	55 (19.2) 1	19 (11.4) 2	36 (30.3)	5 (6.4)	2 (4.5)	3 (8.8)	50 (24.0)	17 (13.8)	33 (38.8)	All: <0.001. Early Adolescents: p 0.086 Late Adolescents: <0.001
Team Sports	106 (37.1) 1	75 (44.9) 2	31 (26.1) 2	42 (53.8)	29 (65.9)	13 (38.2)	64 (30.8)	46 (37.4)	18 (21.2)
Indoor Gym Sports	92 (32.2)	52 (31.1)	40 (33.6)	17 (21.8)	6 (13.6)	11 (32.4)	75 (36.1)	46 (37.4)	29 (34.1)
Team and Gym	33 (11.5)	21 (12.6)	12 (10.1)	14 (17.9)	7 (15.9)	7 (20.6)	19 (9.1)	14 (11.4)	5 (5.9)
MVPA ≥ 60 min/day	190 (66.4)	126 (75.4)	64 (53.8)	61 (78.2)	37 (84.1)	24 (70.6)	129 (62.0)	89 (72.4)	40 (47.1)	All: <0.001. Early Adolescents: p 0.176 Late Adolescents: <0.001
MVPA ≤ 60 min/day	96 (33.6)	41 (24.6)	55 (46.2)	17 (21.8)	7 (15.9)	10 (29.4)	79 (38.0)	34 (27.6)	45 (52.9)

MVPA: Moderate- to vigorous-intensity physical activity. ¹ Percentage of exercise type in the total population. ² Percentage of exercise type for each gender.

). Notably, girls were less engaged in any form of exercise (30.3%) compared to boys (11.4%) (p < 0.001). Among adolescents involved in organized exercise, 37.1% participated in team sports, 32.2% engaged in gym-based activities and 11.5% were involved in both team and gym activities. Boys preferred team sports, while girls showed a preference for individual gym-based activities.

The most popular team sports for boys were basketball, soccer, track, volleyball and water polo, while girls preferred track, volleyball, swimming and tennis. In terms of indoor individual sports, boys preferred weightlifting, aerobic exercise and martial arts, whereas girls preferred martial arts, weightlifting, dancing, rhythmic gymnastics and gymnastics. Regarding compliance with the WHO recommendations for physical activity in adolescents, it was found that 66.4% of the total sample reported an average of at least 60 min of moderate- to vigorous-intensity physical activity (MVPA) per day. More boys than girls met the recommendations, with 75.4% of boys and 53.8% of girls reporting at least 60 min of MVPA per day.

3.3. Family Characteristics According to Adolescent Stage and Engagement in Exercise

As shown in

Table 3. Family characteristics according to adolescent stage and engagement in exercise.

	Early Adolescence		Late Adolescence
	No Exercise	Any Exercise	No Exercise	Any Exercise
Age of mother (in years)	47.0 (45.0–50.0)	47.0 (44.0–51.0)	48.0 (45.0–54.00)	49.0 (46.0–52.0)
Age of father (in years)	49.0 (47.0–56.0)	49.0 (46.0–54.0)	51.5 (47.0–61.2)	52.0 (49.0–55.0)
Marital status (%)	Single: 0.0 Married: 80.0 Divorced: 20.0 Widowed: 0.0	Single: 2.7 Married: 79.5 Divorced: 17.8 Widowed: 0.0	Single: 4.2 Married: 75.0 Divorced: 12.5 Widowed: 8.3	Single: 0.6 Married: 83.8 Divorced: 14.3 Widowed: 1.3
BMI of mother (Kg/m2)	22.8 (22.6–26.5)	23.7 (21.4–25.7)	23.6 (21.6–28.2)	23.9 (21.4–27.1)
BMI of father (Kg/m2)	23.9 (22.0–31.6)	26.9 (25.2–30.6)	27.5 (24.4–30.51)	27.4 (25.3–30.2)
Education of mother (in years)	14.0 (14.0–16.5)	16.0 (13.2–18.0)	12.0 (12.0–16.0)	16.0 (12.0–16.0) **
Education of father (in years)	12.0 (11.0–14.0)	16.0 (12.0–18.0) *	12.0 (12.0–16.0)	16.0 (12.0–16.0) **
Student’s daily hours of studying (in hours/day)	2.0 (1.65–3.0)	2.3 (2.0–3.0)	3.0 (2.0–4.8)	2.30 (2.0–3.3)
Having TV in the bedroom (% yes)	20.0	21.9	24.0	31.8
Student’s daily hours of TV gaming (in hours/day)	3.3 (2.5–5.5)	2.0 (2.0–3.0)	2.2 (1.3–3.1)	2.0 (1.0–3.3)

Comparisons between exercise groups in the same adolescent stage: * p < 0.02 for early adolescence, ** p < 0.007 for late adolescence.

, the education level of both the father and mother (in study years) was higher in late adolescents who were engaged in any kind of organized exercise regime compared to their no-exercise counterparts. The same was noticed but only for the educational level of the father in early adolescence. In addition, the percentage of late adolescents living in a single or widowed family was higher in the no-exercise group.

3.4. Anthropometric Variables According to Engagement in Sport Activities

As shown in

Table 4. (i) Anthropometric variables and KIDMED by type of exercise; (ii) anthropometric variables and KIDMED by type of exercise among early adolescents; (iii) anthropometric variables and KIDMED by type of exercise among late adolescents.

(i)
	Total Population (Ν = 286)
	No Exercise (N = 55)	Team Sports (N = 106)	Indoor Gym Sports (N = 92)	Team and Gym (N = 33)	p1
Age (years)	16.0 (16.0–17.0) a,b,c	15.0 (13.0–16.0) a,d	16.0 (15.0–16.0) b,d	15.0 (14.0–16.0) c	<0.001
Height (m)	1.65 (1.60–1.73) a,b,c	1.71 (1.62–1.79) a	1.70 (1.62–1.76) b	1.72 (1.64–1.79) c	0.009
Weight (kg)	56.5 (52.0–66.6) a	62.0 (52.7–68.5)	64.5 (54.3–72.4) a	65.3 (52.4–70.6)	0.074
BMI (kg/m2)	20.7 (18.6–22.9) a	20.8 (19.2–22.6) b	21.4 (20.1–24.0) a,b	20.7 (18.6–23.8)	0.037
Body weight categories
Underweight (%)	12.7	2.8	2.2	3.0	0.196
Normal weight (%)	70.9	79.2	73.9	72.7
Overweight (%)	12.7	14.2	17.4	18.2
Obese (%)	3.6	3.8	6.6	6.1
FFM (kg)	22.7 (20.1–30.3) a,b,c	28.2 (22.5–32.9) a	27.9 (22.9–33.7) b	30.1 (22.4–34.6) c	0.004
FM (kg)	13.8 (7.6–18.0) a,b	9.4 (6.0–13.4) a,c	12.4 (8.7–16.5) c,d	9.85 (4.35–13.6) b,d	0.001
FM (%)	22.5 (14.6–30.7) a,b	16.6 (10.2–22.6) a,c	19.6 (13.9–26.3) c,d	13.6 (6.75–20.9) b,d	<0.001
ΒΜR (kcal/day)	1275.0 (1176.0–1558.0) a,b,c	1467 (1264–1631) a	1452 (1273–1649) b	1547 (1311–1710) c	0.002
KIDMED score	5.0 (3.0–6.0) a,b,c	6.0 (4.0–8.0) a,d	6.0 (4.0–7.0) b,e	7.0 (6.0–9.0) c,d,e	<0.001
(ii)
Early Adolescents (N = 78)
	No Exercise (N = 5)	Team Sports (N = 42)	Indoor Gym Sports (N = 17)	Team and Gym (N = 14)	p
Age (years)	13.0 (12.5–13.5)	13.0 (12.0–14.0)	14.0 (12.5–14.0)	14.0 (12.7–14.0)	0.075
Height (m)	1.65 (1.56–1.71)	1.67 (1.55–1.78)	1.63 (1.59–1.74)	1.64 (1.60–1.76)	0.892
Weight (kg)	55.8 (44.0–60.7)	55.4 (46.7–64.8)	58.4 (53.6–63.6)	51.6 (48.1–63.2)	0.652
BMI (kg/m2)	19.6 (16.8–22.8)	19.5 (17.5–20.9)	20.1 (19.2–22.1)	19.2 (17.5–22.8)	0.484
Weight categories
Underweight (%)	0.0	2.4	0.0	7.1	0.945
Normal weight (%)	80.0	78.6	82.4	71.4
Overweight (%)	20.0	14.3	11.8	21.4
Obese (%)	0.0	4.8	5.9	0.0
FFM (kg)	22.7 (17.8–23.8)	25.2 (20.3–31.9)	25.0 (21.9–30.7)	24.0 (20.0–26.4)	0.359
FM (kg)	14.7 (6.0–21.1)	7.1 (4.5–12.9)	11.1 (5.2–16.0)	5.7 (2.1–14.1)	0.249
FM (%)	25.8 (14.4–34.8)	14.0 (8.6–22.6)	20.8 (10.1–26.7)	11.6 (3.4–25.6)	0.206
ΒΜR (kcal/day)	1275 (1104–1314)	1354 (1177–1602)	1351 (1238–1558)	1312 (1198–1411)	0.419
KIDMED score	5.0 (2.5–7.0)	6.0 (4.7–8.0)	5.0 (3.5–9.0)	7.0 (5.5–8.2)	0.329
(iii)
		Late Adolescents (N = 208)
	No Exercise (N = 50)	Team Sports (N = 64)	Indoor Gym Sports (N = 75)	Team and Gym (N = 19)	p
Age (years)	16.5 (16.0–17.0) a,b	15.5 (15.0–16.0) a,d	16.0 (15.0–16.0) b,d	16.0 (15.0–17.0)	<0.001
Height (m)	1.65 (1.59–1.73) a,b,c	1.73 (1.66–1.79) a	1.71 (1.64–1.76) b,d	1.74 (1.71–1.81) c,d	<0.001
Weight (kg)	58.25 (52.0–67.25) a,b,c	63.9 (56.85–71.07) a	66.5 (54.8–77.4) b	70.0 (62.9–72.8) c	0.006
BMI (kg/m2)	20.75 (18.67–22.9) a	21.20 (20.0–23.1)	21.7 (20.4–24.7) a	22.4 (20.2–24.8)	0.066
Weight categories
Underweight (%)	14.0	3.1	2.7	0.0	0.158
Normal weight (%)	70.0	79.7	72.0	73.7
Overweight (%)	12.0	14.1	18.7	15.8
Obese (%)	4.0	3.1	6.7	10.5
FFM (kg)	23.0 (20.32–30.95) a,b,c	30.4 (24.1–33.5) a	29.1 (23.2–34.7) b	32.6 (30.0–35.8) c	<0.001
FM (kg)	13.20 (7.55–17.85)	11.0 (7.4–13.6) a	12.7 (9.1–16.8) a	10.5 (5.1–13.6)	0.094
FM (%)	1283.0 (1179.0–1283.0) a,b	16.8 (11.8–22.6) a	19.5 (14.1–25.6) c	14.4 (8.4–18.2) b,c	0.002
ΒΜR (kcal/day)	1283.0 (1179.0–1567.0) a,b,c	1541.0 (1320.0–1657.0) a,d	1505 (1284–1692) b,e	1642 (1546–1736) c,d,e	<0.001
KIDMED score	4.5 (3.0–6.0) a,b,c	6.0 (4.0–7.7) a,d	6.0 (4.0–7.0) b,e	8.0 (6.0–9.0) c,d,e	<0.001

¹: p for comparison between groups after Kruskal–Wallis test. ^a, ^b, ^c, ^d, ^e: The same letter indicates a significant difference between groups. BMI: Body Mass Index. FFM: fat-free mass. FM: fat mass. BMR: Basal Metabolic Rate.

i, when comparing anthropometric variables between active and inactive participants in the total population, the exercise groups demonstrated improved body composition (in terms of fat-free mass, body fat and, consequently, BMR) compared to the inactive group. Furthermore, when these variables were compared among the different types of exercise, the team sports group exhibited the best body composition profile in comparison with the other exercise groups. In the early adolescent stage (Table 4ii), there were no significant differences between the groups, whereas in the late adolescent stage (Table 4iii), there were significant differences between the non-exercise group and all of the other groups in terms of height, weight, FFM and BMR. More details of the differences between the exercise groups are presented in Table 4iii.

Specifically, the Kruskal–Wallis test indicated a significant difference in fat-free mass, body fat and BMR across the four different exercise groups. Post hoc comparisons using Dunn’s test with Bonferroni correction for multiple testing revealed that the fat-free mass of the inactive group was significantly lower than that of all other exercise groups. Moreover, participants in the team sports group had significantly lower total body fat than both inactive participants and those in the indoor gym sports group. The BMR of the inactive group was also significantly lower than the BMR of all other exercise groups. However, no significant differences were found between the groups regarding weight.

Similarly, significant differences were observed in anthropometric characteristics between students who reported a daily average of at least 60 min of moderate to vigorous physical activity and those who did not meet the WHO guidelines. As indicated in

Table 5. Anthropometric variables and KIDMED scores according to compliance to WHO physical activity guidelines.

	MVPA ≥ 60 min/day			MVPA < 60 min/day
	Total Population (N = 190)	Early Adolescents (N = 78)	Late Adolescents (N = 129)	TotaL Population (N = 96)	Early Adolescents (N = 17)	Late Adolescents (N = 79)
Age (years)	15.0 (14.0–16.0) #	13.0 (12.0–14.0) *	16.0 (15.0–16.0) *^	16.0 (15.0–17.0) #	13.0 (12.0–14.0) *	16.0 (15.0–17.0) *^
Gender (% girls)	33.7 #	39.3	31.0 ^	57.3 #	58.8	57.0 ^
Height (m)	1.71 (1.62–1.78) #	1.64 (1.58–1.76) *	1.73 (1.66–1.78) *^	1.67 (1.62–1.74) #	1.68 (1.61–1.71)	1.67 (1.62–1.75) ^
Weight (kg)	62.7 (53.4–70.0)	54.0 (46.5–62.8) *	66.4 (57.3–72.8) *^	60.1 (53.2–68.4)	59.1 (52.8–66.3)	60.4 (53.2–68.6) ^
BMI (kg/m2)	20.8 (19.2–23.2)	19.5 (17.7–20.9) *	21.4 (20.3–23.8) *	21.1 (19.4–22.9)	20.4 (19.3–21.6)	21.3 (19.4–23.0)
Weight categories
Underweight (%)	3.7 #	3.3	3.9	6.3 #	0.0	7.6
Normal weight (%)	76.8 #	78.7	76.0	71.9 #	76.5	70.9
Overweight (%)	16.8 #	16.4	17.1	12.5 #	11.8	12.7
Obese (%)	2.6 #	1.6	3.1	9.4 #	11.8	8.9
FFM (kg)	28.3 (22.9–33.6) #	23.8 (20.2–30.6) *	31.2 (25.2–34.9) *^	24.6 (21.3–30.8) #	25.1 (22.8–29.1)	23.8 (21.1–31.3) ^
FM (kg)	9.7 (6.0–13.8) #	6.7 (4.3–12.4) *$	10.9 (7.5–13.8) *^	13.9 (9.5–18.7) #	13.4 (8.7–19.2) $	13.9 (9.7–18.5) ^
FM (%)	16.3 (10.5–21.7) #	13.3 (7.1–24.9) $	16.6 (11.6–21.2) ^	23.3 (15.1–30.1) #	22.9 (14.6–31.9) $	23.3 (15.1–30.1) ^
ΒΜR (kcal/day)	1472 (1288–1657) #	1310 (1179–1554) *	1575 (1369–1705) *^	1340 (1279–1508) #	1353 (1280.0–1550.0)	1314 (1221–1573) ^
KIDMED score	6.0 (5.0–8.0) #	7.0 (5.0–8.0) $	6.0 (5.0–8.0) ^	5.0 (3.5–5.5) #	5.5 (4.7–8.2) $	5.0 (3.0–6.0) ^

Results are presented as medians (25th–75th Percentile). * p ≤ 0.05 for between adolescent stages in same MVPA group. # p ≤ 0.05 for comparisons between total population engaging in MVPA ≤ 60′ per day and total population engaging in MVPA ≥ 60′ per day. $ p ≤ 0.05 for comparisons between early adolescents engaging in MVPA ≤ 60′ per day and early adolescents engaging in MVPA ≥ 60′ per day. ^ p ≤ 0.05 for comparisons between late adolescents engaging in MVPA ≤ 60′ per day and late adolescents engaging in MVPA ≥ 60′ per day. BMI: Body Mass Index. FFM: fat-free mass. FM: fat mass. BMR: Basal Metabolic Rate. MVPA: Moderate- to vigorous-intensity physical activity.

, students who complied with the WHO guidelines had a significantly lower total body fat and fat percentage, as well as a significantly higher height, fat-free mass and BMR, compared to students who did not comply. Moreover, early adolescents who met the WHO guidelines exhibited a better body composition profile in terms of body fat mass and percentage, as well as BMR, than those who did not meet the recommendations. Almost the same results were noticed in late adolescents who met the WHO guidelines; they presented a lower FFM, body fat mass and percentage, and BMR compared to those who did not meet the WHO guidelines. Early adolescent students who met the WHO guidelines presented lower body weight, BMI, FFM, body fat mass and percentage, and BMR in relation to late adolescents students.

3.5. Adherence to the Mediterranean Diet According to Gender and Engagement in Sport Activities

The KIDMED score of the total population indicated medium adherence to the Mediterranean Diet pattern. No significant differences between the KIDMED scores of boys and girls were observed (Table 1), or, as shown in Table 4ii, between different types of exercise groups. However, a significantly higher KIDMED score was noted in all groups of active adolescents compared to the non-active group (Table 4i,iii). A comparison between the different types of exercise revealed a significantly higher KIDMED score in the team and gym group compared to the other two groups in Table 4i. In late adolescents (Table 4iii) significant differences between the non-exercise group and all the other groups are presented, as well as differences between the team sports group in relation to indoor gym sports group and team and gym group, differences between indoor gym sports group compared to team sports group and team and gym group and differences between team and gym group compared to team sports group and indoor gym sports group. The same result was observed between adolescents who complied with the WHO recommendations of 60 min of moderate to vigorous physical activity per day and those who did not comply (Table 5). More specifically, early adolescent and late adolescent students who met the WHO guidelines showed better KIDMED scores than those who did not comply.

To identify which aspects of dietary habits contributed to the higher KIDMED scores in the exercise groups, we compared the responses to each question of the KIDMED questionnaire (

Table 6. Eating habits according to gender and engagement in exercise in late adolescents.

	Late Adolescence (N = 208)
	All (N = 208)		Boys (N = 123)		Girls (N = 85)
Eating Habits	No Exercise (N = 50)	Any Exercise (N = 158)	No Exercise (N = 17)	Any Exercise (N = 106)	No Exercise (N = 33)	Any Exercise (N = 52)
Q1: Takes a fruit or fruit juice every day	62.0	77.8 *	47	79.2 *	69.7	75.0
Q2: Has a second fruit every day	28.0	31.0	11.8	32.1	36.4	28.8
Q3: Has fresh or cooked vegetables regularly once a day	70.0	80.4	52.9	78.3 *	78.8	84.6
Q4: Has fresh or cooked vegetables more than once a day	26.0	29.7	17.6	30.2	30.3	28.8
Q5: Consumes fish regularly	6.0	25.9 *	5.90	25.5	6.1	26.9 *
Q6: >1/week to a fast food restaurant	62.0	69.0	64.7	69.8	60.6	67.3
Q7: Likes pulses and eats them >1/week	46.0	69.0 *	52.9	68.9	42.4	69.2 *
Q8: Consumes pasta or rice almost daily	64.0	70.9	64.7	71.7	63.6	69.2
Q9: Has cereals or grains for breakfast	60	62	52.9	60.4	63.9	65.4
Q10: Consumes nuts regularly	20	31	5.9	28.3 *	27.3	36.5
Q11: Uses olive oil at home	98	96.2	94.1	94.3	100.0	100.0
Q12: Skips breakfast	64	69	58.8	68.9	66.7	69.2
Q13: Has a dairy product for breakfast	50.0	70.3 *	58.8	72.6	45.5	65.4
Q14: Has commercially baked goods or pastries for breakfast	78.0	84.2	88.2	84.0	72.7	84.6
Q15: Takes two yoghurts and/or some cheese (40 g) daily	30.0	47.5 *	5.90	43.4 *	42.4	55.8
Q:16 Takes sweets and candy several times every day	60.0	70.9	76.5	74.5	51.5	63.5

Results are presented as percentages of a positive results to each question. * p < 0.05 for all late adolescence exercise vs. no exercise.

). We present the results only for the late adolescent group since the classification of the early adolescent group into gender and exercise subgroups led to very few cases of each subgroup, which did not allow for a valid statistical analysis. A higher percentage of late adolescents in the exercise group answered positively to questions Q1 (Takes a fruit or fruit juice every day), Q5 (Consumes fish regularly, at least 2–3 times per week), Q7 (Likes pulses and eats them >1/week), Q13 (Has a dairy product for breakfast, such as yogurt or milk) and Q15 (Takes two yogurts and/or some cheese, 40 g daily). The higher percentage of positive answers to questions Q1, Q7 and Q15 can be attributed to boys, while the higher percentage of positive answers to questions Q5 and Q13 can be attributed to girls.

4. Discussion

This cross-sectional study explored the relationship between frequent participation in organized exercise, body composition and adherence to the Mediterranean Diet (MD) among Greek adolescents in the Attica region. It is well established that physical activity provides several physical, mental and cognitive benefits to young people. Both aerobic and resistance exercise, in combination with nutritional programs, have been shown to improve body composition and metabolic parameters, whereas physical inactivity is associated with several detrimental health outcomes [33,34,35,36,37,38,39,40,41,42]. The findings of this study revealed that 80.8% of the adolescents engaged in regular sports club activities, while 19.2% did not participate regularly in sports, with more boys (88.6%) than girls (69.8%) participating in regular exercise activities. Additionally, among girls, a higher proportion (30.3%) were not engaged in any form of exercise compared to boys (11.4%). This result suggests that while the majority of Greek teenagers follow a regular exercise regimen, there is still a significant difference between genders, with boys participating more actively than girls. Similar gender differences have been observed in other studies, indicating that boys tend to be more active than girls across Europe. This gender disparity is consistent with other European studies, such as Eime et al. (2019) and Emmonds et al. (2024), which report higher male participation in sports across age groups [60,61]. Possible reasons include greater access to sports opportunities for boys and gender differences in competence, especially in skills like ball handling [62,63]. Another study by Marcues et al. showed similar results [64], while a study by Grams et al. showed that Spanish girls were less active than Spanish boys [65]. Furthermore, the percentage of early adolescents (6.4%) not engaged in regular exercise is significantly lower in comparison with late adolescents (24.0%). This may be explained by the fact that older adolescents face more intense school pressures and abandon or minimize other recreational activities. The relationship between youth involvement in organized physical activities and fitness could be confounded by pre-existing fitness levels and socioeconomic status. In our sample, paternal and maternal education were found to be significant determinants of adolescents’ regular engagement in sport activities. Adolescents whose parents had a higher level of education presented a lower percentage of inactivity compared to those whose parents had a lower level of education. Fitter youth may self-select to engage in these activities, while those from families with greater resources may have enhanced nutritional and physical activity opportunities, potentially influencing their fitness outcomes.

In terms of body size and composition, significant differences were noted between boys and girls in height, body weight, FFM, body fat percentage, visceral fat and BMR. The difference in height might be explained by the fact that the more physically active group may had a higher level of physical maturation or that their height provided some advantage for athletic participation. It should be noted that no exercise group was more likely to be underweight and not obese. This may be explained by their dietary options, possibly attributed to their socioeconomic characteristics. Regularly active adolescents generally had better body composition, although subgroup analysis did not find significant differences between active and inactive boys and girls. The differences in body composition between active and non-active adolescents likely stem from the higher proportion of boys in the active group. This aligns with studies like Manzano-Carrasco et al., which found higher fat mass in pubertal girls and more muscle mass in pubertal boys, with no significant differences in BMI between the two sexes in the pubertal stage [66]. A meta-analysis by Mateo-Orcajada et al. also showed lower body fat, fat mass and fat mass index in active adolescents compared to their sedentary peers [40]. This suggests that moderate to vigorous exercise leads to long-term fat loss, while sedentary behavior is associated with fat accumulation, especially in the abdominal region [67,68]. In addition, Galan-Lopez et al. found a higher percentage of body fat in girls in relation to boys, whereas the higher levels of lean body mass in boys explained their higher ability to attain higher levels of strength, speed and cardiorespiratory fitness. However, this could also be due to a higher level of physical inactivity or sedentarism in girls, a fundamental determinant of NCDs [44,69,70].

Regarding dietary habits, adolescents showed moderate adherence to the MD, with a median KIDMED score of 6.00. However, physically active adolescents had better adherence to the MD, consistent with findings from other studies. The same results were observed when this analysis was conducted separately for boys and girls; for instance, Galan-Lopez et al. (2018) and Muros et al. (2017) reported a positive relationship between high performance in a resistance test and MD adherence [44,71]. Similarly, Evaristo et al. (2018) showed a relationship between high adherence to MD and both high levels of health-related physical fitness and high levels of health-related quality of life [72]. This relationship may be explained by the fact that both behaviors, adherence to healthy diet and regular engagement in physical activity, are constituents of a healthy lifestyle and depend on the motivation, rooted in the perceived value of health, of individuals and their families, which influences the adoption of health-promoting behaviors.

According to the KIDMED questionnaire, the healthier nutritional habits of active adolescents were due to better adherence to the prudent habits of eating one serving of fruit a day, eating fish regularly, eating pasta or rice five or more times per week, eating nuts at least three times a week, consuming dairy products during breakfast and having two yogurts or cheese daily. In the group of active boys, the higher KIDMED score was attributed to the greater consumption of fruits, vegetables, nuts and dairy products. In addition, the group of active girls had a better adherence to the MD than inactive girls by eating more vegetables, fish, legumes and dairy products in their breakfast.

These findings have been confirmed by several studies. Moradell et al. showed in the HELENA study that adolescents who met the physical activity (PA) guidelines and screentime recommendations had higher intakes of healthy foods (e.g., fruits, vegetables, and dairy products) [73]. Lopez-Gil et al. found significant associations between PA levels and MD scores [74]. Food choices such as cereals, fruits and vegetables appeared more likely in the diets of active adults and children than in inactive groups [75]. Lazarou et al. (2010) found that children who maintained high levels of PA adopted healthier dietary choices [74,76,77]. In addition, Ottevaere et al. found higher fruit intake in active males compared to the lowest-PA group [78]. Finally, the German KIGGS study (second wave) found associations between PA levels and consumption of healthy food and beverages in German children and adolescents [77]. The exercise groups participated in physical activities outside of school; thus, their personal resources may have allowed them access to better diet options as well as improved opportunities to participate in club activities.

The present study has some limitations that should be discussed. First, this was a cross-sectional study; therefore, it is not possible to demonstrate a causal relationship between the variables studied. Second, the sample size was relatively small and the findings of the present study are not representative of the Greek adolescent population; while the results are not generalizable to all adolescents in Greece, the results likely have implications regarding the impact of adolescent dietary choices and participation in organized physical activities on adolescent health. Nevertheless, the participants were recruited from all areas of the Attica region, where more than 50% of the total Greek population lives. Another limitation of this study is the low participation rate among schools and the adolescents. Despite efforts to recruit a larger sample, the study faced several challenges. Participation was limited due to several factors: a lack of agreement to participate from a significant number of schools; low parental consent for eligible students, which aligns with previous research indicating adolescent and family hesitancy to share personal information or undergo body measurements due to privacy concerns; the fact that data collection was constrained by school curriculum priorities; and other objective problems (such as absence due to illness, exams, etc.) on the data collection day. Moreover, the questionnaires that were used were self-reported; thus, there is a possibility that some participants reported eating habits and physical activity engagement that did not actually describe the real situation. Nevertheless, in order to ensure that the participants completed the questionnaires as unaffectedly as possible, anonymity was ensured. Furthermore, the study tools did not aim to examine the motivations and barriers to recreational physical activity, considering self-perception, peer and socioeconomic influence and available access to physical activity options. Finally, the use of a bioelectrical impedance analyzer such as an impedance scale is not the gold standard for estimating the percentage of FFM.

5. Conclusions

This cross-sectional study among Greek adolescents living in the Attica region highlights that boys participate more frequently in organized sports compared to girls. Additionally, it was revealed that teenagers living in the Attica region who engage in regular exercise exhibit better body composition and healthier eating habits than their non-exercising peers. These findings underscore the benefits of physical activity and the Mediterranean Diet during adolescence, a critical period characterized by rapid physical and psychological changes. Regular participation in organized sports can lead to significant long-term health benefits, including improved cardiorespiratory fitness, regulation of body composition (such as fat mass, body weight and BMI) and overall well-being. Future research should aim to address the motivations for and barriers to recreational physical activity, as well as to explore the interplay between nutrition and exercise in adolescents to understand how these lifestyle choices impact long-term health outcomes. Given the profound changes occurring during adolescence, this research is vital for guiding interventions that promote healthy behaviors and prevent chronic diseases.