you 5 yr old weigh?

*Not sure if this is the right spot but someone please move if it wrong*

My Son will be 5 in September and we noticed over the last few weeks he really doesn't eat much.. He is extremely thin.. He is 110cm tall and weighs 18kg..

you can see his ribs and when he is leaning over slightly is spine just sticks out.

I know he has gotten taller but surely that wouldn't just explain the sudden thin ness..

We are going to take him to the Dr on monday but I was just curious what others weighed at this age

oh and also should mention he is generally still active.. he is a little tired this week as he has a tiny cold