The purpose of the study was to determine the change in body weight and body mass index (BMI), as well as diet behaviors at 4 months after intervention between obese adolescent girls who participated in the school-based nutritional education program, addressed by pediatrician, compared to those who attended regular nutritional class. Methods: 49 obese girls were recruited from a secondary school. Those, were randomized into 2 groups of intervention and control. The intensive interactive nutritional program was provided to the intervention group. Weight and height, dietary record and % fat consumption, as well as self-administered questionnaires on healthy diet attitudes were collected at baseline and 4-month follow-up, and then compared between two groups. Results: There was a statistically significant change of BMI in the intervention group by 0.53±1.16 kg/m² (P = 0.016 ) compared to the control group ( 0.51±1.57 kg/m²,P = 0.063 ) but no significant change in calorie and % fat consumption between groups. The attitudes on healthy eating behaviors in the intervention group were shown improving significantly (P <0.001 ). Conclusions: Interactive and intensive nutritional education program as shown in the study was one of the most successful school-based interventions for obese adolescents.