Background: Inconsistent results have been reported about the relationship between low RMR and obesity. The purpose of this study was to investigate the relationship between RESTING METABOLIC RATE and body composition factors in obese and normal weight gymnastics children. Materials and Methods: 20 obese and 21 normal-weight boys, aged 8-12 years, participated in this study. In the first session, data regarding the participants’ anthropometrical (weight, height, waist to hip ratio (WHR)) and body composition (body fat percentage (BF%), body fat weight (BFW), and lean body weight (LBW)) measurements were recorded. In the next session, at first, subjects rested for 15 min and then performed a modified Bulk exhausting test. The subjects were connected to the mouthpiece of gas analyzer throughout the rest and exhausting test and VO2max, RER, and RMR were conducted in both groups. Results: Significant difference was observed for a mean of VO2max, weight, BF%, BFW, LBW, and WHR between the two groups (P=0/001). The mean of RMR per kg body weight was significantly lower in the obese group than in the normal-weight group (P<0/05). There was no significant difference in the RER variable between the two groups (P>0. 05). There was a significant linear relationship between RMR with weight, WHR, BFW, LBW, and VO2max in the obese group (P≤ 0/05). Conclusion: Based on the results of the present study it can be concluded that the difference between the weight of obese and normal-weight beginner gymnast children is partly due to low RMR; and the lower RMR in obese children might be due to their low cardiorespiratory fitness.