I just made a special meal request, at the bottom of the page:
> If you can't find a suitable meal from the options we offer, you're welcome to bring your own food. Please ensure it doesn't require heating or refrigeration. Also remember to plan your meal around the security screening restrictions on liquids, pastes and gels.
So go wild!
You're allowed to bring an amount for "consumption during your trip". I've brought fast food from outside and eaten it on the plane. TSA had no issues. I regularly pack a few bags of chips/fruit when flying on short trips.
I also bring a refillable water bottle.
I have frequently brought a full meal through. For my last trip I had a to-go box in my hand as I walked through security (so it wasn't hidden in my bag).
The only time I ever had a problem was when my meal was a burrito wrapped in aluminum foil, and there I just got a secondary search.
You can buy food once you're in the secure area, of couse, but it's generally quite expensive.