Fats are good for a slow, long burn. You'll get those out of nuts, chocolate, cheese, sausage, that kind of thing.

Protein is a very slow burn, nor does it burn as hot, but it makes all kinds of nasty waste products, so you'll need more water. Most animal protein sources have a lot of salt in them, so you need even more water.

Trick is, those aren't fast burst foods. These are entree, hunker down type things, because you won't want to be doing much that needs blood out at the limbs while you are digesting these. At least I don't.

One good thing to look at might be halva. Am_Fear recently brought it up, and I think it has been mentioned before. I'm always partial to Joyva, and it fine frozen.