I agree with Eric Bailey about the calorie burn and appetite lose. Just the high altitude ups your calorie burn. They say it takes two weeks for your body to adjust to what your doing to it. If your out that long your appetite may catch up, but otherwise I think the only way you could keep up would be to take a day off during the week, and who's going to do that? I try to minimize weight lose but it always happens. Getting your weight up before you go can help.
I look at calories per ounce when choosing what to take. I have found energy bars to be a waste, except maybe for the Snickers Marathon bar. Most have a lot of sugar and I can't get ten feet on one. For breakfast I have Old Fashioned Oatmeal with Nido freeze dried whole milk, Spiru-tein protein powder, and raisins. Sometimes I add peanuts. Just add it with boiling water to a insulated bottle and let it cook. Nature's Path Pumpkin Flax Granola can be substituted for for the oatmeal for a faster breakfast, but cold. I plan to add flax seed meal to the mix this year (something I read). Oberto's pork jerky, peanut M&M's, cashews, dried tomatoes, walnuts, and peanuts are good snacks. Mountain House is good. The Sweet & Sour and Chili Mac with Beef are my favorite, two serving size only. Get the propak type or it gets bulky fast. Mission Wraps (Walmart) are good, high calorie, hold up well, and can be used with the MH chili mac to make a burrito. I also carry Bear Creek freeze dried soup (Walmart). Tortilla and Hot & Sour are my favorite. I add twice the recommended amount to boiling water in the insulated bottle to up the calories. Tyson's sausage crumbles are good if the OAT cooperates and are high calorie. Add to the Mountain House or the soup. High fat is good. Foil packaged tuna IN OIL and salmon are good for lunch and when taking a break. I also take Alpine Apple Cider mix. Great before getting into the tent for the night and helps you get more water down. Hard boiled eggs are good for the first few days, but I don't do that much. A frozen steak would be good the first day too, but you would have to build a fire, and I never do that.
A hiking buddy goes all week on peanuts, raisins, and jerky. Thats all he eats all week, every snack, every meal. For me variety is important, otherwise consumption goes down.