matt and i are big into hiking and backcountry camping. one of the things we have learned through our experience is that LIGHTER is BETTER. when you're hiking 10, 12 km to a campsite, you want to cut back on the weight in your pack as much as possible. but, that being said, it's also really important to bring enough food - you burn a lot of calories doing trips like that, and it's important to eat enough to keep up your strength (never know when you'll have to fight a bear!! okay, that doesn't happen... yet?)
things like trail mix and granola bars (and holy shit, chocolate covered pretzels - why did nobody ever tell me how amazing they are???) are great nutrient-dense, easy trail foods.
since i'm slightly obsessive about making things myself, and because i feel a heck of a lot better about eating things when i can pronounce all of the ingredients, i have been making my own granola bars!
they are really easy to make, keep well, and are such a great on-the-go snack. you can wrap them in plastic wrap or tinfoil (or better yet, reusable plastic bags!) to grab in a pinch.