Drink as much as possible. You can survive much longer without food than you can without water. Even if you do eat, you still need water in your system in order to metabolize that food, much in the same way that wood needs oxygen in order to burn. Many people find that meat is not a necessity when backpacking. Protein in sufficient quantities can be found through many lighter foods that won't spoil, such as nuts, beans, and peas.
Peanuts are fairly high in protein, as well as lentils.
Jerky, in all it's wonderful forms, is great for its flavor and munchability. Plus, it won't spoil the first day you hit the trail. Carbohydrates keep your muscles fed with energy, and also help to keep your body warm as well. Fat, typically, is not a desired food item during the regular hustle and bustle of everyday life. At least not if you listen to TV commercials.