MBP and LMWP were positively associated with obesity in boys in a concentration-effect manner. In the 11–13 y group, LMWP level was positively associated with all obesity indices, including subscapular ST, WC and HC, %BF, BMI, BMIZ, and BSA. The Q3 and Q4 of MBP were significantly associated with higher BSA, BMI, BMIZ, subscapular ST and HC.In girls, inverse associations were found between urinary MEHP, MEHHP and ∑MEHP and obesity (p=0.05). The gene discussed is MBP; the disease is obesity due to melanocortin 4 receptor deficiency.