I am a runway model and they like you to look tall, elegant, and thin but not to this, am 5'8ft and weigh 48kg and I model on the runway.
Well you have to have a pencil shape to your body that goes straight down meaning you have to be well porportioned but as for commercials and photos, the requirments are different.
There are different types of models. Runway models are expected to be tall and thin. (Think human hangers) Commercial modeling doesn't have such strict requirements.