Hey, you look so thin, are you ok？
嘿，你看上去好瘦啊，你还好吗？
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.
这个词就是表示，瘦的跟皮包骨似的。
Slim describes someone who is not too thin but looks healthy.
苗条，就是指这个人看上去不是特别瘦，看上去很健康。
Petite is used to describe girls who are short and slim.
娇小的，用来形容女生比较苗条，还比较矮。
Lean means someone who is slim.
lean 通常用来形容比较瘦的男生。

She is a dancer, she looks petite.
她是一个舞蹈演员，她看上去很娇小。
He is lean because he is a long distance runner.
他很瘦，因为他是一个长跑运动员。

Obese is someone who is not fit at all and has more fat than usual.
Obese 指的是过度肥胖。
chubby
胖乎乎的 （指微胖）
Curvy: usually to describe a woman who has a great body but she is not slim.
有曲线的，前凸后翘的，不瘦不胖。