What I am going to say is this. The people who think weight doesn't matter are wrong. And the people who think weight is the only thing that matters are wrong. And when you get down to the heart of it, none of us really believes either of those extremes either. The truth lies somewhere between.
Now this study, done by a doctor and published in a medical journal proves one thing really well: People will take one very limited study (sample size of one!) and if it confirms their notions of how they think things are (or should be) they'll point to it as "scientific proof". It's not.
I walk to work these days. The trip is four blocks over flat terrain. I could randomly flip a coin to decide if I'm going to wear sandals, running shoes or hiking boots for my commute. Let's say I track my commute times for six months and they turn out to be exactly the same. From this do we conclude that I'm an idiot for having three different kinds of footwear? Or do we conclude that people who buy sandals are idiots? Or do we conclude that, yes, I really do have too much time on my hands?
Over the years I actually have bike commuted various distances (depending on my jobs my bike commute has been as short as a mile each way to 20 miles each way) and I have found that weight of my commuting bike is one of the least important factors to commute times. On my commutes I've found many factors that matter more than weight. Timing at stoplights, traffic, wind & other weather all have a much greater impact than dropping a couple of pounds off the weight of my bike frame. But in other circumstances, a difference in weight can be an appreciable difference.
Weight isn't trivial. Ounces add up to pounds and when the road goes up you notice those pounds. Ask any experienced bike tourist if weight matters or not. If they've been on the road for a while, the odds are they've sent some things home. And it's not just about speed, sometimes it's about comfort. I'm sure many a tourist has packed panniers and trailer with all the comforts of home only to realized when climbing some mountain pass that those comforts aren't making them very comfortable at all.
It comes down to figuring out how much weight matters to you, in your circumstance. I remember being in my first real road race, more than thirty years ago. It was a hundred-plus mile road race and as we neared the end, I saw one of the fast guys, the guy who tended to win everything, pour the water out of his bottle. "Lightening up for the sprint," my buddy told me. The rest of the peleton took this as a cue and we all started tossing full bottles and Silca pumps into the ditch. I swear I saw the color of at least a few jersies shift to red as the hammer dropped and the sprint ripped the pack to pieces. Weight mattered a hell of a lot in those few seconds.
For commuting and your commute, maybe weight isn't what you need to worry about. Analytic Cycling is a good site for those of us who like to play with numbers to see how various factors relate to bicycle riding. Weight matters a bit and so do lots of other things. At the end of the day we all get where we're going.
Keep 'em rolling,
Kent "Mountain Turtle" Peterson
Issaquah WA USA