Childhood and adolescent obesity has become one of the most vital challenges to overcome in the present age. Physical fitness, physical activity and the Mediterranean diet (MD) are valuable tools for its prevention and treatment. The main objective of this study is to analyze the associations between health-related physical fitness components, body composition and adherence to the MD in 917 adolescents aged from 13- to 16-years-old. The ALPHA-Fitness Test was used to measure physical fitness and body composition, and the Adherence to the Mediterranean Diet (KIDMED) questionnaire was employed to assess the adherence to the MD. The associations between variables were tested according to gender and age a generalized linear model (GLM) univariate analysis (two factors) and one-way analysis of variance (ANOVA, with Bonferroni posthoc). As to the body composition and physical fitness variables, significant differences were obtained in both genders but not in relation to the adherence to the MD. The boys performed better in the physical fitness tests. Age was a determinant factor in adherence to the MD in the total sample, lowering as the age of the sample increases. Both the boys and girls who had a significantly higher performance in the endurance test were those who showed high/medium adherence to the MD. It is concluded that higher levels of cardiovascular endurance in boys and girls are associated with a medium and high adherence to the MD.

Childhood and adolescent obesity are currently among the greatest challenges for public health. Physical activity, physical fitness, and adherence to the Mediterranean diet (MD), representing powerful indicators of healthy lifestyles, are shown as determinant factors in the prevention and treatment of obesity. The aim of the present study has been to analyse the relationship between health-related physical fitness components, body composition, and adherence to MD in 387 Icelandic adolescents of 13–16-years old (54% boys). The ALPHA Fitness Test was used to measure physical fitness and body composition. The KIDMED questionnaire was used to assess the adherence to MD among participants. Associations between variables were tested according to gender and age using linear regression models and analysis of variance. Participants with high/medium adherence to MD showed significantly higher endurance scores in both the boys and the girls. Gender differences were found. The boys in high/medium MD categories had significantly lower fat percentages and ran a 4 × 10 m sprint faster than the girls. The girls scored higher than the boys in endurance and speed-agility tests. It can be concluded that a high and medium adherence to MD is associated with high and very high endurance in both the girls and the boys.

Sleep is a vital element of adolescents’ overall health; it influences their body and mind and thus affects their quality of life. Adequate sleep quality and duration are essential for maintaining optimal metabolic health and lowering the risk of developing several medical conditions, such as cardiovascular disease. The current study aimed to assess the perceived sleep quality and duration of 1717 European adolescents from three different European countries (Spain, Iceland and Estonia) aged 13- to 16-years (900 boys, 817 girls) using the Pittsburgh Sleep Quality Index (PSQI). A multivariate analysis of variance (MANOVA) was performed to examine differences between groups and two-factor analysis of variance (ANOVA) was used to analyze city and age differences. The probability of having poor sleep quality and duration was calculated by Odd-Ratio (OR). Our study found poor sleep quality in 44% of the boys and 53% of the girls, whereas 68% and 69%, respectively did not get the recommended hours of sleep (i.e., 8–10 h). No difference was found between adolescents from Estonia, Iceland and Spain regarding sleep duration. In contrast, Spanish and Estonian adolescents reported higher probabilities of having poor sleep quality. Finally, girls had a significantly higher probability of poor sleep quality than boys.

This study aimed to investigate the role of self-identity, defined as salient and enduring aspects of one’s self-perception (Sparks, 2000), in relation to adolescent physical activity (PA) intentions within the Theory of Planned Behaviour (TPB). School students aged 12 to 18 from two cultural groups (Estonia and Spain) completed measures of attitudes, subjective norms, perceived behavioural control, self-identity, and intentions for PA. Four weeks later participants completed self-reported measures of PA. A structural equation model showed that self-identity had a direct effect on PA intention (β = .33, p < .01) and PA behaviour (β = .31, p < .01). The model accounted for 45% of the variance of PA behaviour from which 4% can be attributed to self-identity. The effect of self-identity on PA was also partially mediated via intention. The multi-group comparison between two cultural groups indicated that no invariances existed between the models of the observed samples.