Resumen Introduccion. La composicion corporal ha demostrado ser un importante indicador de salud. Objetivo. Analizar la Composicion corporal en escolares de 13 a 14 anos, pertenecientes a la zona centro y sur oriente del Tolima. Materiales y metodos. Participaron 335 estudiantes (Hombres 49,9%; 50,1% mujeres) con rango de edad 13-14 anos. Se evaluo IMC, perimetro de cintura y porcentaje de grasa. Los instrumentos fueron: bascula, tallimetro y cinta metrica. Resultados. Se encontraron diferencias de genero en las variables estudiadas, con mayor IMC y porcentaje graso entre las mujeres (20,4kg/m2 vs. 19,0kg/m2 y 26,2% vs. 17,6%, respectivamente); sin embargo, el perimetro de cintura fue similar en los hombres y mujeres (68,2 cm vs 68,1cm). En ambos sexos, la edad se asocio con aumentos del IMC (p<0,05) y con el porcentaje graso entre las mujeres (p<0,05), al contrario de lo que ocurrio en los hombres, donde la edad se asocio inversamente con la grasa corporal (p<0,05) y el IMC. Conclusiones. Se deben generar estrategias orientadas a cambiar habitos alimenticios y promover la actividad fisica escolar. Palabras clave: indice de masa corporal; adiposidad; genero; cintura. Abstract Introduction. Body composition has been an important health indicator. Objective. Analyze body composition in schoolchildren aged 13 to 14, belonging to the central and southern area of Tolima. Materials and methods. 335 students participated (Men 49.9%; 50.1% women) with age range 13-14 years. BMI, waist circumference and fat percentage were evaluated. The instruments were: scale, height meter and measuring tape. Results. Gender differences were found in the variables studied, with higher BMI and fat percentage among women (20.4 kg / m2 vs. 19.0 kg / m2 and 26.2% vs. 17.6%, respectively); however, the waist circumference was similar in men and women (68.2 cm vs 68.1 cm). In both sexes, age was associated with increases in BMI (p <0.05) and with the fat percentage among women (p <0.05), contrary to what happened in men, where age was associated inversely with body fat (p <0.05) and BMI. Conclusions. Strategies oriented to change eating habits and promote physical school activity should be generated. Keywords: Body mass index; gender adiposity; waist.