Background: Self-efficacy in obese children is significantly lower compared to normal weight children. Exercise program has positive impact on one's body composition and self-efficacy. The purpose of this study was to examine whether voluntary participation exercise program improves obese children's self-participation in exercise.
Method: Participants within the 85th percentile or higher body mass index (BMI) values were enrolled. They were divided into either self-exercise group (n = 14) or control group (n = 14). Body composition and self-efficacy were measured before and after the 12 week intervention program.
Results: Weight (P < 0.05) was significantly decreased after the exercise program. BMI and percentage of fat were also decreased but the decrease was not statistically significant. Percentage of skeletal muscle (P < 0.05) significantly increased after the exercise program compared to the pre program value. Self-efficacy (P < 0.01) significantly increased after the program and it showed significant positive correlations with height, skeletal muscle mass, skeletal muscle to weight ratio, but manifested significant negative correlation with %fat in all participants. Positive change in self-efficacy showed significant negative correlations with change in weight, BMI and fat mass among the control group.
Conclusion: This study shows that voluntary participation exercise program may be a useful intervention method to improve weight, BMI, skeletal muscle mass, and self-efficacy in obese and overweight children.

Keywords: 자기효능감, 신체조성, 비만아동, 운동