Here's a few common sentences that we use in daily life to say that we are hungry!

#1 SPEAK LIKE A FRENCH PERSON : To be hungry.

I'm starving ! 
Really popular expressions used by young people instead of J'ai faim.  You should use it when you want to eat a lot.

Popular expression to say that you are really hungry.

I'm a bit hungry. ''Creux'' means something empty inside.
So its an image to say '' my stomach is a bit empty''
French people offently say ''J'ai un petit creux'' when they want to eat a little snack, ice cream...