Can you be a size 16 to be a teen model?

It will be very unlikely due to the fact that fashion and runway models are required to be sizes 0-4 and plus size models are generally between the sizes 12-18 (size 10 plus size models are not as common but are sometimes needed). It seems that you are somewhere in the middle and unfortunately, there is no market in the modeling industry for aspiring models that fall in between.