Gorp.. huh? What's that?

As for stuff high in calories; up here in Canada, the military has these little pouches of high calorie food called LMCs (Light Meal Combat). They're pretty much these vacuum sealed pouches of high calorie candy, fruit, and so on.

Dried papaya, mango, and banana, chocolate bars, pop tarts, nuts, juice crystals with little pouches to throw them in and add some water in to make a sweet drink, freeze dried cheese (Yeah, it's as gross as it sounds!), jerky, and so on. They're designed to give soldiers a high calorie boost while doing winter exercises.

Trust me, marching around all week with a pair of snow shoes and a ruck sack on your back burns a lot of calories.