OP if you're still on here and reading these responses I'm finding this to be quite amusing, man, you ask a simple question and you certainly get a deluge of answers don't you?
I've read all your posts and you sound to be quite reasonable. I don't think you're starving your children. I don't think you're being controlling of their food.
In fact I think you're being quite generous by including extra pocket money and allowances for them to buy what they want when they want. (I never had that growing up, I worked three jobs from the time I was 12 to the time I was 19 to be able to afford whatever I wanted and mostly, what I wanted was to save for University so I almost never got snacks)
The fact that they're going through the cupboards at night and eating all your food like a bunch of locusts more likely is because they are bored / think they're hungry but they're not really hungry.
I'd almost guarantee it although yes it is true that growing teenagers do require more calories, more than likely this is boredom snacking.
And what you're mentioning about them using up all the condiments and all the dips and all the sauces in the fridge? Yeah, I have a sibling like that. A condiment that should last a family of six four to six weeks, he will consume in two sittings and see nothing wrong with it because he likes dips and sauces, loves to slather them all over his food.
And it's so incredibly frustrating because, you sound like you're the main person who does the grocery shopping and planning, and making the meals. And if you think there's something in the fridge that you're going to use for supper and then you come down in the morning and it's all been consumed, you just throw your hands up and go what the hell!!
And no, mentioning that your children go into the freezer to open and eat the packages of sweet corn and peas and all that kind of thing, that's not abuse for God sakes, I used to do the same thing. They're large packages, relatively inexpensive, I'd pour half a container of frozen peas into a bowl, microwave it, throw a knob of butter on top, and eat it as a snack. I still do.
And for those saying that your daughters eating frozen sweet corn is going to give them food poisoning, are the girls actually eating at Frozen and uncooked? Or are they cooking it first such as heating it up in the microwave or on the stove top? I really doubt they're eating it frozen like ice cream but if they are, then yes, there can be a listeria contamination just like with anything else that's raw, raw foods there's always an increased chance of a contaminant. Cooking the food does decrease that risk. There's nothing inherently wrong with sweet corn. So, I think you're getting a bit of alarmist advice on that front.
If your daughter's like to snack on frozen vegetables and you can get huge (like 2 to 5 kg sized family packs) a frozen vegetables that they like, then yeah, if it's inexpensive, tell them to snack on that. It'll work out too inexpensive per gigantic serving even though that should be enough for an entire family meal, and they're eating it in one night, well, at least there's a lot of fiber in it.
I hate to say it but if they're being that locust like in their eating habits, where you go downstairs and you've got a full kitchen and you come down in the morning and all the food is gone, you might have to lay some ground rules for them, this isn't being controlling, this isn't being abusive, they're the ones who are out of control and abusing the family open food policy.
But if I were you, aside from putting limits on things (like for instance, you each can have one banana after 8:00 p.m. only please, I don't want to come downstairs and find that 8 bananas are gone)
Consider purchasing huge family sized bulk portions of inexpensive filling food such as low sugar cereal, frozen vegetables, and air popped popcorn. All those things are very cheap and can be filling. And more than likely it's not that they're eating because the poor girls are so hungry and they're starving, it's just because they feel in a snacky mood so they reach for the first crunchy / salty / sweet easy to find thing that they can find.
There's a difference between eating out of hunger and eating out of habit. A lot of people can't tell the difference.