Talk to Pediatrician on Childhood Problem Of 8 Yr

My 8 year old daughter is having eating and listening problem. she never had urge to eat and when we try to talk her out and ask to chew the bite she is having in mouth she dont listen to me or her mother even beaten. Somone ask me to consult a psychiatrist. We have consult many pediatricians for medicines related to hunger but it does not work. she is also under weight (12 kgs at 8 year age).