I was assuming the styrofoam had zero weight, actually. But food isn't pure carb and protein and fat, it has lots of water. Looking at my labels, my bread is under 3 cal/g, my hot dogs are 2, eggs are under that, *dry* pasta is under 4.
http://www.calorie-count.com/calories/item/20421.html
gives similar numbers for chicken or cooked noodles, say.

I'd also looked up lo mein and sweet and sour chicken, but there was a wide range of values, from under 1 to 3.