"I am hungry."
To fully explain we need to break down the sentence to see what is literally being said:
[My, implied] おなか [belly, stomach] が すきました [became empty]。 すく means "to become empty".
In order to be hungry now, one's stomach must have already become empty. This is just how it is expressed.
I'm sorry, that totally slipped my mind; you'll have to be set to a different language on web to get there for now. I usually come to the website to comment and search for the question. I had wanted to avoid copying and pasting the same info, but I guess I'll edit my comment; though a user above has now answered.
(EDIT-just realized I didn't read @DemiMurgos comment properly, and that he basically said everything I said in less words...)
That's not the reason why it's rude. It's ok to say your hungry as long as you say it politely. はらへた is very casual and impolite. The classroom uses polite speech. Use お なか が すきました。
The polite parts here are the use of お- (o) as a prefix for politeness, and also the use of the past tense polite form sufix -ました (mashita). When you omit them and use a slang, of course it's going to come out impolite. Casual speech is extremely common in anime, which is why anime isn't recommended for learning japanese (until you want to speak casually with your close friends).
As far as the male speech part goes, that's only true in casual language. It's not that women "can't" say it. It just sounds really awkward. It's the language equivalent of cross dressing. And guys aren't immune. Male tourists and immigrants that learn female casual speech from thier female teachers get fun poked at them for speaking like a girl until they learn. But all of this doesn't matter until after you learn polite form.
I was hungry (when I was walking home, for example) = お腹が空いていました. That's because being hungry is a state, right?
When you realize you're hungry, it happens in an instant, so お腹がすきました has it like "(I just realized) my stomach has become empty." When it doesn't surprise you or your companion anymore, you might say お腹がすいています - "My stomach is empty (and has been for some time now)." I don't think there's a big difference here between すきました and すいています though. Except if you want to say "I'm still hungry" when you've already eaten something - that would be お腹がまだ空(す)いています。
Literally it means - My stomach is emptied (technically this is passive but it sounds marginally better than my stomach emptied) - therefore if your stomach has already been emptied you are currently hungry. So.... おなか が すきました is translated as "I am hungry". Please take the time to read other comments on this thread before asking questions - this question has been asked and explained multiple times.
I'm not really good at grammar so maybe you can write the example and I can help you out.
Anyways, the reason why they use past tense in the sentence「お腹が空いた」it's because is an expression you use in a way that you just realized that "ohh... my stomach got empty", that's how they use it. The translation into "I am hungry" is just a way to make the sentence in english have meaning.
Also why caps? frick you man, it hurts my eyes.