Hey, you look so thin, are you ok？
嘿，你看上去好瘦啊，你還好嗎？
He is way too skinny for my taste.
他太瘦了，不是我的菜。

Scrawny means someone who is so thin that their bones can be visibly clear on their body.
這個詞就是表示，瘦的跟皮包骨似的。
Slim describes someone who is not too thin but looks healthy.
苗條，就是指這個人看上去不是特別瘦，看上去很健康。
Petite is used to describe girls who are short and slim.
嬌小的，用來形容女生比較苗條，還比較矮。
Lean means someone who is slim.
lean 通常用來形容比較瘦的男生。

She is a dancer, she looks petite.
她是一個舞蹈演員，她看上去很嬌小。
He is lean because he is a long distance runner.
他很瘦，因為他是一個長跑運動員。

Obese is someone who is not fit at all and has more fat than usual.
Obese 指的是過度肥胖。
chubby
胖乎乎的 （指微胖）
Curvy: usually to describe a woman who has a great body but she is not slim.
有曲線的，前凸后翹的，不瘦不胖。