How can you tell if your leopard gecko is eating?

I usually put few Cricket in her tank and leave for a bit min sense she doesn't eat when I'm there with her and i comes back making sure the cricket are not hiding or die in her water. I do this a lot just in case such as feed then wait then comes back and wait and sometimes in the middle of the night. Now i was wonder because she looks fat ( not her tail) I'm not to sure if she would eat it or just eat her shed?