thin person
skin and bones
scrag

The thin person cannot displace an amount of water equal to his/her weight.

"Starveling" is a word for a thin or poor person lacking food.

I met a thin person once who ate one Lay's potato chip and stopped.

One possibility is that none of their responses will work as a thin person.

I am a small and thin person and being fat was great!

A moment later the front door opened and a thin, dark person appeared.

She was a small, thin, quick-moving person with large dark eyes.

Start living life like a thin person, and make breakfast a healthy habit.

One person's fat is another person's thin and so forth.

The thinnest person, a woman of some height, ordered for the group.