In short, the theory that everything tastes better on trail (i.e. while hiking, camping or especially backpacking). Long hiking trips bring out the gourmand in everybody. The premier example of this is brown sugar and cheese, which probably sounds horrible, and is, at sea level, but completely and utterly rules the world at altitude in the backcountry after a few hard miles.
Another example of the principles of backcountry flavor (sometimes pronounced "backcountry flava") in action: I am a bagel snob of the worst variety. Strictly speaking, I refuse to believe there exists any such thing as a real bagel west of the Hudson River, and don't even start with me on those plastic-wrapped, donut-shaped lumps of probably not even boiled before baking dough that pollute the shelves of grocery stores. So full of preservatives you can't even pound nails with 'em after a day... *shudder*. The one exception to this snobbery of mine is at altitude. Even the most horribly repulsive, preservative-filled, storebought pseudobagels taste like joy on trail; there's few better ways to ingest a quarter pound of bread in a hurry. Yum.
Most recently, while hiking some 70 miles of the Pacific Crest Trail with a friend who'd devoted several months to that endeavor and invited all her friends to join her for one- or two-week intervals of the same, I was introduced to the concept of stove-free hiking. This involved, much to my dismay on the colder mornings, no hot food. I was seriously worried. Sure, it spared us carrying a lot of extra weight in stove and fuel and fuel bottles, not to mention cooking pots, but how much bread and cheese can a person eat? Answer: half a pound of bread and half a pound of cheese daily, with the bread divided between lunch and dinner. The extra calories were made up of Luna Bars and other granola bar spinoffs, hummus and other spreads (mmmm, olive tapenade), and lots of chocolate. Damn, chocolate is good stuff, and never better than after a long uphill. Sugar and fat, something my body needs anyway!
But for me the best backcountry flavor discovery of the trip was the packages of predrained tuna. Have they come to your local grocery store yet? Marketed for convenience, these plastic-foil envelopes contain ready-to-eat tuna goodness, chunk white or albacore (mmmm, albacore), in water or oil (mmm, oil). Now, I love tuna. Lots. So much that it's one of the greatest obstacles between me and becoming a vegetarian. I eat it straight from the can at home when I'm craving protein... but the typical can of tuna is four ounces, minus water drained off. On the last dinner of our trip, I ate half a pound of tuna singlehandedly. It was pure bliss, and I couldn't eat tuna for weeks after that binge, even after I got home and had been eating normally for some time. Backcountry flavor drove me to it.
The moral of the story: Everything tastes better on trail. But don't take advantage of this lightly.