Body weight is not always the best indicator of health and a thin person still needs to eat well and exercise regularly.

体重并不总是健康的最佳指标，瘦的人仍然需要吃得好，有规律地锻炼。

youdao

If a thin person eats a lot, I'll follow suit.

如果一个瘦的人吃很多，我就会跟着吃很多。

youdao

What happens when a thin person takes a small portion?

那么，当和一个胃口很小的瘦子一起吃饭时又会如何呢？

youdao

At about nineteen-thousand meters, the air is so thin and the amount of oxygen so small that a person needs a lot of special equipment to survive.

VOA: special.2011.04.06

Conversely, BMI may underestimate body fat in a very small-framed person, someone who has very little muscle mass, or a person who carries his or her excess weight mainly around the midsection and has very thin arms and legs (the so called apple shaped body type).

CNN: Can BMI be adjusted for muscular builds?