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The viral 12-3-30 workout possesses all the hallmarks of a typical TikTok fitness trend: a self-descriptive name, an easy-to-remember hashtag, and the promise of an easier way to burn fat—in this case, by walking on a treadmill for 30 minutes at three miles per hour and a 12 percent incline. Naturally, the workout also came with an entirely anecdotal success story, which helped it gain popularity. Influencer Lauren Giraldo claimed to have lost 30 pounds by doing the incline walking routine five times per week. However, with the publishing of a recent University of Nevada study, the 12-3-30 workout now also has something else going for it: peer-reviewed research. It’s the reason why you might have seen this trend bubbling back up into your feed. In addition to validating the fat-burning effects of the 12-3-30 workout, the study also pits it against running, and even determines that walking at an incline can burn fat at a higher rate than a self-paced run. But what does that mean for you, and is the study as straightforward as it seems? We talked to the experts to find out. What does the research actually say? The study, published in a recent edition of the International Journal of Exercise Science, set out to compare the metabolic impacts of incline walking (specifically, the 12-3-30 workout) and running. To make sure they were comparing apples to apples, the researchers matched the workouts for calorie expenditure. In other words, subjects burned the same number of calories while doing both activities. With this common denominator, the researchers were then able to observe how the two activities differed in terms of their total time and rate of calorie expenditure, as well as the amount of fat and carbohydrates that each activity utilized for fuel. 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). “If you had one person walking consistently to lose fat and you had another person running consistently to lose fat, the individual that is burning more calories is going to see more results, because at the end of the day this all usually comes down to calories in versus calories out,” says Ghafari. In this case, that person would be the runner. Run or walk, if you are so inclined If there’s a positive headline to take away from this incline walking vs running study, it should be that people who are unable to run have another effective, research-backed way to burn fat. “Incline walking is easier on the joints [than running], and it's just something you're probably more likely to do,” Dr. Del Toro Badessa says. “As a coach and nutrition educator, I love 12-3-30 for certain goals and populations,” says Ghafari. “For those on GLP-1s, those returning from injury, or people building aerobic capacity, incline walking builds strong metabolic foundations without jacking up joint strain.” The research is also a reminder to runners that you can adjust the pace of your runs to achieve different goals. For example, you could get the exact same fat-burning effect from running as you would from the 12-3-30 workout, simply by training with a heart-rate monitor and keeping yourself in zone two. No wearable? No problem. “The easiest test is if you can carry on a conversation,” says Dr. Del Toro Badessa. “f you're able to talk in a full sentence while still running, then you are probably in the fat oxidation zone. In a self-paced run, you're probably in more of a zone three, and pushing zone four sometimes. You tend to go into higher aerobic, cardiometabolic zones with these self-paced jogs where you can't necessarily speak.” At the end of the day, the best fat-burning exercise for you will be the one you enjoy the most (or hate the least) and you’re able to do consistently, says Dr. Del Toro Badessa says. “The best workout that you can do for yourself is one that you're going to do again.”
