If you're backpacking for a day or a weekend, you can take whatever food you like and enough fresh water to keep you sated. But if your hike is going to last several days, you need to pack the right type of foods and be prepared to find natural sources of water.
Hiking and backpacking burns a lot of energy. According to the Appalachian Trail Conservancy, hikers should pack between 1.5 to 2 pounds (.68 to .91 kilograms) of high-calorie food for every day on the trail. Don't bring any cans, or foods, such as vegetables and fruits. Fruits and vegetables are high in water and heavy to carry. If you're hiking in cold weather, it takes more calories to stay warm. As such, the ATC advises hikers to bring 2.5 pounds (1.13 kilograms) of food per day [source: Appalachian Trail Conservancy].
Snacking on the trail is encouraged. Snacks, such as chocolate, energy bars, dried fruit and nuts are good for a quick nibble and can easily be transported. In fact, it's better to constantly snack instead of eat large meals. Snacking gives you more energy [source: Appalachian Trail Conservancy].
Chances of finding a water cooler on any trail are nil. Before heading out, know where natural springs and other fresh water sources are located. Plan carefully, because these sources can dry up in the summer [source: Appalachian Trail Conservancy].
Boiling is one way to purify water. Another is to treat it with iodine or chlorine tablets. Although boiling is time consuming, it's the best way to destroy bacteria and other organisms that can cause illness. Let the water boil fiercely for at least one minute.
Water filters are also handy. If you're going to be using a portable water filter, make sure it's from a reliable manufacturer. Although some water filters claim to remove certain types of bacteria and organisms, they may not [source: Appalachian Trail Conservancy].