I'm gonna add some stuff here. Crunches burn very little calories, but it is very good or building core strength. I would continue building up all your core muscles, as a strong foundation will prevent the house from breaking (aka, injuring yourself, strains, etc). Don't forget to stretch either. You should try some strength training beyond crunches, as muscle mass burns more fat than fat does (In other words, you'll burn calories watching TV with muscle vs fat). 15 minutes on the treadmil is alright, but I hate to say it, and this is what gets me to give up almost every time... it just isn't enough. You really got to up the ante here to burn those calories. Walk more, jog longer, take the stairs, jumping jacks, jump rope... however, begin at a pace you are comfortable with. Do too much too fast and you'll burn out or worse, you'll hurt yourself.
Also, I'm not sure how much you know, but doing crunches won't get rid of your belly. Spot training to get rid of fat does not work. You just gotta burn it out of ya. I still recommend you keep doing crunches.
Also, doing any sort of muscle work will tire yourself out and leave yourself open to injury. When you build muscle, you get small tears in your muscle fibers. Your body also used up all kinds of energy and chemicals that the muscles use. If you don't give your body time to rest, you'll be doing more than just burning out and being frustrated that you can't do as much as you did last time: you can seriously hurt yourself. I work out Tues, Thurs, and soon to be Sat.
As for food, eat 6 times a day, small meals, full and hearty. I don't know what the good combo is, but a nutritionist said protein for breakfast, not carbs. Carbs later, but that's all I remember from her, and saddly I no longer have my notes that I took.
However, poor eating or not eating enough does more than make you crumble to a gorge-fest. Your metabolism slows down as well, meaning your body will conserve energy and not burn as many calories idly as say, a high metabolism. So when you break down and pig out (like I do ^^; ) then those 1000 calorie meals will take longer to burn off than if you pigged out with a high metabolism.
Also, don't kill your muscles! Well, don't lose muscle mass at least. Eat protein, drink protein, inject protein... just get protein! Also, I would take vitamin supplements to make up for anything you may be lacking. I often have more energy when I do take them. Do your research on those though, Vitamin A = bad, so don't take more than whats recommended. Vitamin D = bad, but thats harder to OD on. Several other things are bad, like the metals they add and what not (I've been reading alot on Vitamins). Fish oil is good too, just got to be careful of the brands you get, else you might get some nasty mercury laden oil (but don't be too afraid to actually, you know, do it, just exercise some caution is all).
I'm not an expert and I still have trouble keeping up with the stuff. I'm just going off of what I've read from official sources, such as experts, books, etc, and from what I learned back in the day of weight lifting.