Backpacking trips are essentially like endurance events. It's OK to eat differently when you're backpacking compared to your regular BB diet. You will be burning mainly carbs and fats for fuel. These should be the backbone of a backpacking diet. Most backpackers burn more calories than they consume so you don't have to worry about getting fat, especially on longer trips. Because many backpackers drink less water than normal, it's a good idea to not eat too much protein. However if you're anal about protein then protein powders are ultra light to carry. Just find one that mixes easily without a blender. But remember that carbs are protein sparing, especially for endurance activities......