Well my kids are now 14, 13, and 11, and from the time they were old enough to ask for anything, they were taught they are not welcome to take whatever they want, they must ask for it. If their chores aren't done they don't get it (not meals of course, but snacks, etc). If they don't finish it, the next time they ask they get told no. If they didn't clean up their mess from it, they get told no. It makes them responsible for whether or not they get snacks. If they eat something sugary for a snack they next day or later that same day they have to eat something better for them. I let them choose from several things on hand, but snacks are not a free for all and sometimes they need to be things like peanut butter and apples or baby carrots, etc. If they get caught stealing the food, yes I consider it stealing, I bought it, they lose snack priveledges for a little while. My kids never go hungry, we aren't on a budget with food to where they will run out of things to eat, but they are responsible for what they take and the mess associated with it. I am more lax on it now that they are older than i used to be, but they still ask, since it's just how it's always been done.