[Grammar] Is Dave ill?

[benjic]

"Is Dave ill? He's lost a lot of weight."
Yes, he's looking very slender these days, isn't he?"

Could a kind teacher please show me where the error is in this sentence and why.
Thankyou

 

[Drear Pooson]

Not a teacher.

To me, slender is thin in a healthy or fit way.

How about gaunt?



DP

 

[5jj]

Even just thin will convey the message you want.