Hi. I Have A Son Who Is 9 1/2. Weighs

hi. i have a son who is 9 1/2. weighs 49 lbs. i constantly worry if he is getting enough. he isnt a huge eater, but excels in schools and never gets sick. has had the flu, once in his life. has great energy, but cant put a lbs on save his life. his father is 6 f 2 inches. i am 5 f 2 inches. We are thin build but he is just bones. i feed him a lot of fat, but keep gluten out for our entire family. but eat very well. is this a concern?
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