天生长不胖英文怎么说

"天生长不胖"通常用英语表示为"naturally thin"或"naturally slender." 这个表达方式源自于英语中"thin"和"slender"这两个词的意思，都表示瘦的或苗条的。

例句：

She has always been naturally thin, no matter how much she eats. (她总是天生长不胖，无论吃多少都是这样。）
He has a naturally slender build and doesn't have to worry about gaining weight. (他天生身材苗条，不用担心会发胖。）