Objectives: Childhood and adolescence are stages in which changes occur both mentally and at a body level and in which habits are acquired that persist for many years in the child's life. The objective of the present study was to analyze body composition and physical fitness based on the practice of physical activity, diet and body image of soccer players at school age. Methods: The sample consisted of 41 players of Alcantarilla football with an average age of 13.12 ± 2.41 years. The following variables of body composition were evaluated: waist / hip ratio (WHR), body mass index (BMI), fat mass (FM), fat-free mass (FFM), total body water (TBW), basal metabolic rate (BMR), fat mass index (FMI), fat-free mass index (FFMI). The physical fitness variables evaluated were: staircase test, resting heart rate (HR), diastolic blood pressure (SBP) and systolic blood pressure (DBP), Course Navette (CN; stage, distance, speed), VO2max, HRmax, HR 1.5, 3 and 5 min post-CN, maximum oxygen saturation (SO2max), SO2 3 and 5 min post-CN. The diet was evaluated using the KIDMED Mediterranean diet adherence questionnaire. Physical activity was assessed using the PACE questionnaire. The body image was analyzed using the Stunkard silhouettes. Findings: The results showed that both the basal metabolic rate (p = 0.002) and the resting systolic blood pressure (p = 0.000) were significantly higher in active subjects than in inactive subjects. Regarding diet, BMI was significantly lower in subjects with a poor diet (p = 0.06) in comparison to subjects with an optimal diet. Finally, according to the body image, the Course Navette result was significantly higher in those who wanted to be larger than in those who were satisfied or wished to lose weight. Conclusions: Therefore, it is recommended to carry out intervention programs to improve the level of physical activity, diet and body image, as this will have a positive effect on body composition and physical fitness.