There is a reason why trail mix has that name. As a rule, nuts pack more calories by weight than any other food. A 1-lb. bag of mixed nuts is a bag with a nourishing 2,700 calories in it, 50 percent more energy than would be found in a pound of straight table sugar. Dried fruits do not pack the same caloric content, although at 80 or 90 calories per ounce they have the same hefty value as cheese. What they bring to the trail mix are vitamins. Most modern dried food packs simply cannot match the virtues of old-fashioned trail mix.
Canned goods are a mixed prospect. They rarely pack the kind of calorie-to-weight ratio to justify hauling them. On the other hand, having a preserved, tasty, prepared food item that can be cooked over a campfire in its own can has its virtues. Soldiers and campers have been dining on Spam and franks and beans for decades, and that can't be all wrong. It's usually a good idea to have some canned items for the sake of variety, but treat them as relishes. They weigh so much that they should never be at the core of a backpacking menu.
Compared to canned meat, dried meat is a lot lighter. That means more protein can be hauled for the same amount of weight. At 70 calories per ounce, beef jerky is actually a little under most dried fruits, but it is a useful source of protein. Another virtue of dried meat is that it is usually seasoned, so it can serve both as meat and seasoning when combined with other foodstuffs in camp cooking. The rule should always be to pack far more dried meat than canned meat, and there is no reason to bring salted meat along at all.
Rice and Beans
Rice has a very low calorie-to-weight ratio from a backpacking point of view, at a measly 37 calories per ounce. Kidney beans are only a little better at 39 calories per ounce. However, both are dried foods that need little more than water and a campfire to cook. They can also be combined with wild herbs, dried meats and foraged foodstuffs like freshly caught fish and edible wild vegetables and tubers to make soups and stews. Few things liven up a camp dinner after a few hard days on the trail than a really good camp stew, and it's hard to imagine one without at least the beans. These are great foods to pack for the sake of variety.
Pasta and Noodles
Pasta averages a solid 110 calories per ounce, and ramen noodles an even better 130. The latter only need water to make into soup, but both ramen and pasta can easily be turned into tasty backpacker meals. A little olive oil and some sun-dried tomatoes (70 calories per ounce) sprinkled with oregano will liven up any camp meal. Ramen can be used to make an improvised lo mein when cooked with a little meat, some soy sauce, and whatever wild vegetables can be found. These are foods that combine tastiness, light weight, a high calorie count and versatility into one solid backpacking package.
Dried Food Packs
Dried food packs of the type found in camping goods stores and served with the U.S. military's MREs have some of the quality of canned food, but with none of the awful weight drawbacks. There are a wide variety of processed meals to choose from, with the military's current MRE menu alone having 24 entrees. The ultra-weight conscious should skip canned goods and go strictly with dried food packs, and in general they are a good idea and worth looking at.