Hi, I had gone through your question and understand your concerns. 50 Kg eight for 9 year child is a cause of concern , you have not mentioned height of child, any family history of obesity, dietary history of child, outdoor activities of child. You are right that before labeling it due to food intake and lack of physical activity , we need to rule out hormonal causes including thyroid status, right department for this is endocrinology/ endocrinologist , better will be combined approach of pediatrician and endocrinologist. Hope this answers your question. If you have additional questions then please do not hesitate in writing to us. Wishing your child good health. • DISCLAIMER: - All the information provided here is for information purpose only , it is not a substitute for the advice of a physician after physical examination , it is not intended to replace your relationship with your doctor. This information in no way establishes a doctor-patient relationship. Before acting anything based on this information do consult your doctor. I recommend that online users seek the advice of a physician who can perform an in-person physical examination