I have three children, one with CF. There is no forcing a child to eat but sometimes it helps to encourage them. My 6yr old with CF eats all the time although he is very thin. My oldest whom is a healthy 11yr old rarely eats. Just be patient and in time it will all fall into place. It gets very frustrating especially when a child has an illness because you tend to worry more. Everyday is a challenge but it does get better!!!!