"In the 20-minute bout," Boutcher says, the actual hard exercise totaled just 8 minutes, "so it's not that much exercise." But the payoff was significant.
Over the course of four months, participants lost an average of 6 pounds of body fat. By comparison, those who cycled at a steady pace for 40 minutes, without mixing in the interval sprints, lost less than 2 pounds.
You can throw all kinds of predator-chasing-prey evolutionary theories at this one, but to me it's just another mark against marathon-style running as a form of exercise. I have never understood why people go running when they can get exercise much more pleasurably -- why not play soccer, basketball, or my sport of choice, racquetball? But as Scott Adams eloquently explains, perhaps the best reason to avoid marathon-style running (at least on pavement or concrete) is your precious knees.
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Related: TIME cover story 8/9: Why Exercise Won't Make You Thin
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Addendum: See the comments for a thoughtful retort from reader Bob.
