I hiked over 5,000 miles on the PCT in Asolo Falcon boots ... and was definitely an outlier. About 90% of thru-hikers wear trail runners. Just ask a typical thru-hiker and you will be greeted by wild enthusiasm for this lightweight, cushy footwear that breathes and dries out quickly. I like the Asolo Falcon boots because they are reasonably lightweight, provide good ankle support, and keep my feet dry everywhere except stream crossings. However ... they are heavier ... and that matters. But how much does it matter?
Let's see if we can figure that out quantitatively for a person weighing 150 lbs. You could pick a different shoe, but to get a comparison, I'll use the Brooks Cascadia 19, with weights per pair from the REI website.
Asolo Falcon: 32 ounces (pair)
Brooks Cascadia: 19: 21.4 ounces (pair)
Difference: 10.6 ounces, or .662 lbs, almost exactly two-thirds of a pound.
The Mountain Tactical Institute did a quantitative comparison of heartrate, backpack weight, and ankle weights and determined that for typical hiking speeds, we can assume that one ounce of ankle weight is equivalent to four ounces of backpack weight. In other words, that 10.6 ounces of additional shoe weight is equivalent to about 42.4 ounces of additional backpack weight, or 2.65 pounds.
Next question ... for a person weighing 150 pounds ... what is the impact on calories and speed of an additional 2.65 pounds in the backpack?
Outside magazine published an article with a calculator in it "The Ultimate Backpacking Calorie Estimator" and we can estimate calorie usage with just a few extra assumptions. Let's assume a 150 pound hiker, 2.5 mph hiking speed, and 7.5% uphill grade (the PCT average), and a 25 pound pack as the base line. Result: 195 calories per mile. Add 2.65 pounds and we get 197 calories per mile, or about 40 calories over the course of a 20 mile hike.
Doesn't a heavier pack slow you down? The Mountain Tactical Institute also looked at that and found "every 1% of your body weight in your pack makes you six seconds slower per mile." So, applying the 2.65 pounds of backpack equivalent weight, for a 150 pound person it will take about an additional 3.5 minutes to hike 20 miles.
So the cost of wearing lightweight boots over a 20 mile hike would be about 40 calories and 3.5 minutes. The benefits of boots are typically: fewer foot problems during the hike, better ankle protection, easier to kick steps in snow, better edging in slippery conditions. Boots also have a downside in addition to weight: they are less convenient for wet stream crossings. Many people will say that you "can't get your boots dry," however I did not find that to be true on my hikes.
Just for fun ... here is my song about ultralight backpacking, which I do think makes sense, but maybe not as an obsession:
