sunken fontanelle

Hi Doctor,
My daughter is 4 years old. Her head is not rounded; because she has sunken fontanelle,her head apex has same as straight pit. Also her chest bones are notable and apparent, same as african famine children.
from birth until 3 years old, she used to **** faeces 3 times to 4 times a day.
She is very thin, although she eat well. What is the treatment for her? Is she have dehydration or less calcium ratio.
Please help me,,,
Thank you very much.