How many calories are you really burning on the treadmill?

Masterfile

Alex Hutchinson of the Globe and Mail recently posted a guest column on Weighty Matters. The blog's obesity doctor, Yoni Freedhoff, asked Hutchinson to answer the question "Can your treadmill really count calories?"

In his response, Hutchinson makes a couple of intriguing points: that if you're less fit than average, you'll burn more than the treadmill guesses, and if you're more fit, you'll burn less. What's more interesting is his pointing out that you really need to subtract how many calories you'd burn, say, watching Glee reruns on the couch from how many you're burning on the treadmill. For a 176-pound woman, that cuts 80 calories per hour from what you're estimated to have burned while exercising.

I'm surprised that he didn't talk about the research that's shown that many machines are not even calculating an average — they're just plain wrong.

A study from the University of California last year compared machines and VO2 analysis — the gold standard of how many calories people burn. Gym machines overestimated calorie burn, on average, by 19 percent; treadmills came in at 13 percent. The worst offender? Elliptical machines, which overestimated the calories you're scorching by 42 percent.