Hi Sir. I Want To Ask That My Age Is

hi sir. i want to ask that my age is 17 and i eat so much because i get hungry very soon when ever i eat i get (poo) due to this i am very skinny and my weight is 45 kg and i am very weak. after 10 to 15 min i get hungry and eat some thing .....i eat healthy food... and do exercise like jogging daily....
plzz tell me then why i am so skinny