These words are banded around a lot in the mountain culture and have made their way into all the various sports that I regularly pursue. From trail running and alpinism, where they make sense, drifting into skiing and even mountain biking.
The fast and light thing makes sense in trail running, where you need the agility and speed to complete objectives. The fast part of this makes sense, but the light really takes a bit of thinking. Knowing the route and your body makes the biggest difference and doing this takes experience.
Knowing your body. ‘Be bold, start cold’ knowing how you warm up means leaving that extra, ‘just in-case layer’ in the car and dealing with the chill as you start moving. Knowing that just a long sleeve capilene layer and a wind-shell will be warm enough, start with both, remove the wind shell as you warm up, roll the sleeves up as you get into the meat of the day and then putting the wind shell back on for the blustery ridge at the summit.
Being able and willing to retreat if things go sideways allows a margin of comfort in your choices and would encourage anyone who is trying out going further faster lighter to have that mental leeway to call it quits or come back another day.
Knowing the route. A small amount of time the evening before allows a lighter approach to be taken. Knowing that half-way through the day you will get to reliable meltwater or safe drinking water allows much less to be carried, and in turn allows a smaller bottle thus saving further weight. Knowing you get to a mountain refuge after two thirds allows a refuel without carrying weight. Knowing a quick and easy retreat allows less just in-case material to be carried. It also lightens the mental load, which may be the biggest load lightener of all!
Weather reports in pretty much anywhere that the fast and light mantra works will be incredibly accurate for 48 hours and the accuracy drops off from there. This allows a freedom of knowing when to commit and when to quit. Failure is not failure if you learn something, whether that is about fuelling, route, gear or technique.
So next time you’re out, try leaving a bit more food at home, leave a bit of water in the car for your return, and experience the mountains unburdened by the weight of the world on your shoulders!