Do you burn more calories if you walk faster?

My exercise of choice nowadays is walking, and my primary reason for exercising is to keep my weight in check, though I also do it because it’s healthy to stay active in general.

Today I decided to answer a question I’ve wondered for a while: when my exercise is constrained by time rather than distance, will I burn more calories if I walk faster?

It may seem like the answer to this question is obviously yes, and indeed that was my working hypothesis which I wanted to prove or disprove, but I’d argue that it’s not actually entirely obvious. For example, if most calorie burning comes from your increased heart and breathing rates, and if you’re in good enough shape that those don’t go up significantly when you walk a little faster, then maybe the difference in your calorie burn rate isn’t significant.

If you’ve been tracking your walks with a fitness watch as I have been for several years (a Garmin), it turns out that this question is pretty easy to answer. Here’s what I did:

• I loaded a list of all of my historical walking activities in the Garmin Connect web app by going to the activities page, filtering it to walking activities, and then scrolling down repeatedly until all the activities loaded.
• I exported the displayed list as a CSV.
• I loaded the CSV into LibreOffice Calc and wrote formulas to convert the HH:MM:SS string Time field into a Time (Hours) numeric field and the MM:SS Avg Pace field into a Speed (MPH) numeric field.
• I added a Calories/Hour field calculated by dividing Calories by Time (Hours).
• I created an X/Y Chart of the Speed (MPH) and Calories/Hours fields.

Here’s the result:

In short, yes, walking faster burns significantly more calories per hour.

Caveat: this assumes that the calorie burn numbers calculated by my watch are accurate, or at least sufficiently accurate to make my calculations meaningful. I am assuming that Garmin knows their business here, but who knows, that may not be a valid assumption.

I figured that now that I’d confirmed that if I want to burn more calories and my exercise is constrained by time then I should walk faster, but what about when my exercise is constrained by distance? If I know in advance how far I’m going to walk, does it matter how fast I walk? This too, is easy to answer:

Well, what do you know. It doesn’t matter how fast I walk if I know in advance how far I’m walking. Good to know!