The headline result, and the reason why people like Bulletproof founder and self-proclaimed biohacker Dave Asprey are talking about the 12-3-30 workout again, is that the study found incline walking to use a higher percentage of fat for fuel than running. Specifically, while incline walking, subjects burned an average of 40.6 percent of their calories from fat, compared with an average of 33 percent for running. That result, on its own, would make it appear that incline walking is more effective at burning fat than running. However, that’s actually not the case at all.
The (real) takeaway you need to know
“Here’s where people get tripped up,” says Joe Ghafari, certified personal trainer, nutritionist, and nutritional educator at the weight-loss company Eden. “The body uses different fuel sources—carbs or fat—depending on exercise intensity. Low-to-moderate intensity, like walking uphill, keeps you in that fat-oxidation sweet spot. That’s what we often refer to as ‘zone two’ heart rate, and it is awesome for building metabolic endurance and improving how your body burns fat over time. But just because you’re using a higher percentage of fat doesn’t automatically mean you’re burning more total fat or hitting a bigger calorie deficit.”
Incline walking may burn a higher percentage of fat for fuel than running, but it also takes much longer to do so. In the data, we can see that running burned significantly more calories per minute than incline walking. Subjects torched an average of 13 calories per minute while running, versus 10 while incline walking. That’s a huge difference. It also means that participants had to run just 23 minutes to burn the same amount of calories as they did with 30 minutes of incline walking.
“The data shows that when matched for total calorie burn, incline walking led to a higher percentage of calories burned from fat compared to running,” Ghafari says. “But it doesn’t mean incline walking burns more total fat. While incline walking uses more fat as fuel percentage-wise, the total fat burned might still be less.”
The fat of the matter
If you’re looking to burn some fat, you really can’t go wrong with either incline walking or running—although running will probably still get you there faster, due to the overall higher calorie burn. Ultimately, the success of your weight-loss efforts will hinge on your ability to maintain a caloric deficit.
“If you’re trying to lose weight and lose fat, the answer is a run, because of the caloric expenditure,” says Cristina Del Toro Badessa, MD, wellness physician and director at tktk Artisan Beaut.
In the study, incline walking burned about 22 percent more calories from fat than running did. But the subjects only ran for 23 minutes, which is 25 percent less time than they spent incline walking. So, with a little back-of-the-napkin math, we can see that running would actually utilize about the same amount of fat as incline walking over the same period of time (while also burning roughly 25 percent more total calories).
