【了】liao v finish；complete；adv completely entirely 【没吃了】have not eaten up completely 。

People in China don't use 没吃了 了 can't be used in negative

没吃:上一次没有吃。 没吃了:以前吃过，但已经不吃了。

我们不用“没吃了”这个词，“了”表示已经发生的事情，比如“我到了”，意思是“我到达这里”这件事已经发生。如果还没有吃饭，只用“没吃”就可以表达了。

沒吃 didn't eat 『還』沒吃 haven't eaten yet 『有段時間』沒吃了 didn't ate sth for a while only saying 沒吃了 doesn't make sense to me. u have to add time before it.