The concept is simple: cut the combined weight of all your gear to a fraction of what you typically carry, and then go twice as far as you otherwise would. Not so simple is executing the concept. It's easy enough to go and buy the lightest pack, sleeping bag and shelter, but will you be prepared for a night or two (or more) in the woods with your system? Are you ready for the weather? You need to make sure you are prepared for the same conditions you'd expect on a standard trip when you are on a fast and light trip.
The reality is that to go light you need to think differently. You need to think about what you're bringing, how you are using it, how you can be more efficient. Here's an example: In standard backpacking the rule is to have at least 2 liters of water (4 1/2 pounds) with you. When I hike the Rae Lakes Loop, a 45 mile trip through Kings Canyon, I carry one 21 oz. bike sized water bottle, which carries 1 1/2 pounds of water. Why carry 4 1/2 pounds of water with you as you are hiking by a stream? I fill my bottle whenever it's empty, and keep myself well hydrated, but never carry more than the one small bottle, saving 3 pounds.
The key to successful fastpacking is developing a system. Anything you carry should have multiple tasks.
Let's take a look at some packs to start. I use a Golite Team pack when I am going light. The pack weighs about 2 lbs. Right there I am saving close to 6 pounds compared to my standard backpack! The team pack has almost no padding in it, and no structure or frame to it. If you were to load it up like a standard pack you'd be in for an uncomfortable hike for sure. The first thing I put in my pack is my foam sleeping pad, rolled up into a hollow cylinder, and lowered into the pack verticallly. The sleeping pad becomes the back pad for the pack, as well as a "soft frame" for the pack, and it protects the nylon pack skin from sharp objects inside the pack.
Now how about a sleeping bag. The key here is to go as light as possible while still staying warm at night. Above all else, get a sleeping bag that fits you well. If the bag is too big, you'l be carrying too much weight and too much bulk, but more importantly you'll be colder in a bag that is too big for you. Do you need a 20º degree bag on a 20º night? What if you sleep with a hat on? What if you fill a nalgene bottle with hot water and throw that in your bag with you before bed? What if you sleep a little closer to your tent mate and conserve body heat? Do some situps in your sleeping bag to generate some heat before you fall asleep, or if you wake up in the middle of the night.Do you think you could get away with a 30º bag? It'll save you a pound or more!
Do you need a tent? Seriously, do you? Why? If you hike in the Sierras in summer, it is unlikely to rain on you at night. A tent does provide a sense of privacy, but is a few minutes of privacy worth carrying 5 pounds through the woods all day? If you feel you need to carry a tent, try going simple, small and light. A sil-nylon tarp can be strung up between two trees, or between two trekking poles to provide shelter if you need it. In addition to being light (about a pound) and simple, these tarps pack down to the size of a grapefruit. Less gear volume equals less pack volume, which equals a lighter and more comfortable pack. If you feel you must have a more traditional tent, look for something small and light. Something that weighs around 3 pounds, like the Golite Trig 2 or Eisenhower Tunnel tents. These tents are light, but you do need to pitch them with consideration to the wind, to get some ventilation in the tent.
Once you have these harware items taken care of , you can start focusing your attention on your clothes. Are you bringing a change of clothes? Why? leave it behind. Are you wearing everything at night? If not, you can probably leave some more behind. All your clothes should work together in a layering system, and you should be wearing everything you have at night. Are you wearing a hat to keep warm?
How about stoves, and cooking pots. I've become pretty partial to the Jetboil system on fast and light trips. Jetboils stoves are a compact system that incorporates a stove, pot, cup, and even a french press for coffee, although I have to confess to using high quality instant coffee on my fast and light trips. The Jetboil boils water quickly, and efficiently. The fuel weight savings can be significant. Titanium pots and cups are another option, but the titanium cups get really hot.
And fast and light food? Even if you bring good food, try to make it fast food. Part of the fast and light equation is moving quickly and efficiently. An hour spent cooking could have been an hour of hiking. Look for food that either just needs to be heated, or cooked briefly.
Once you have your gear list pared down to the minimum, you'll see your pack is significantly smaller and lighter. One of the big dividends is hiking in trail runner type shoes rather than hiking boots. You save weight and gain comfort.
Plan your days wisely. Get up early in the day and start moving right away. I will often pack up my sleeping bag and start moving, while eating a Clif or Luna Bar, and I'll stop to make coffee after an hour of hiking. Similarly, sometimes I'll stop for dinner, then hike as far as I can until it's too dark to continue. Obviously there are limitations to this plan if you are in a big group, or if you need to make it to a designated site.
It's important to remember that fastpacking isn't for everyone. If your perfect backpacking trip involves cooking trout on the cast iron skillet your father used when you were young, by all means bring the cast iron skillet! But if you want to lighten your load, and see how comfortable backpacking can be, give the fast and light program a try.
If you're interested in reading more, here's a couple of good books on the subject.
Richard Bothwell