Basic rule-of-thumb trail math I use for calories is 100 cal/oz for carbs and protein, 200 cal/oz for fats. That's for completely dry grocery store stuff like pasta, rolled oats and nuts. I shoot for a mix that gives me about 130 cal/oz average. I carry about two pounds, about 4000 calories, per day (including some fresh fruit and veg that really blows the weight budget, but I think is necessary for long-term trail nutrition).

Like Dogwood says, if someone comes up with 250 cal/oz trail food, that's a breakthrough. Or like he says, flavored olive oil, and you really don't want to live on that. I haven't tried it, but have stories of those who have and it's not pretty. (And nearly fatal in one case and that's a long story.)