June 25, 2025, 2:24 pm | Read time: 7 minutes

Many recreational athletes often ask themselves the same question: Which sport is best for burning body fat? A study compared incline walking with running—and the findings were surprising.

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Walking Uphill on the Treadmill? A Good Idea!

In the cardio area of a gym, you’ll find people engaged in various endurance sports: some are running on the treadmill, others are rowing or using a stepper or elliptical trainer. And then there are those who walk uphill on the treadmill at a steep angle. This method is called Incline Walking. It may look a bit unusual, but it is actually an effective way to burn fat, as a study shows.

In recent years, a specific workout with Incline Walking has become established: it’s called “12-3-30” and was invented by fitness influencer Lauren Giraldo. The American spread the workout on social media and claimed to have lost about 29 pounds in two years with it alone, without dieting. The formula is easy to break down:

• The treadmill is set to a 12 percent incline.
• The walking speed is three miles per hour, which is about five kilometers per hour.
• The workout lasts 30 minutes.
• You should not support yourself with your arms.

Researchers Compared Incline Walking with Running

In a study published in the journal “International Journal of Exercise Science,” American researchers wanted to compare the metabolic activities of the 12-3-30 workout with those of self-paced running.¹ They recruited 16 participants who were at least 18 years old. Seven were female, and nine were male. All were from the university environment of the University of Nevada in Las Vegas (USA). The average age of the participants was 25.3 years, and the average weight was 166 pounds. They were healthy participants without significant overweight who exercised regularly.

Excluded from participation were individuals who were pregnant or could be, suffered from chronic underlying conditions such as diabetes, heart disease, or kidney disease, or did not meet the inclusion criteria for physical fitness.

Within one week, participants had to complete a self-paced run and a 12-3-30 treadmill workout. During the self-paced run, they chose the intensity and speed that felt comfortable. However, participants had to stop running once they burned the same amount of calories as in the 12-3-30 workout.

The duration of the self-paced run and the energy consumption, broken down into carbohydrate and fat consumption, were measured.

Incline Walking Led to Better Fat Burning

The data analysis provided interesting results. Participants burned calories faster while running. However, they relied more on carbohydrates than fat as an energy source. In contrast, during Incline Walking at lower intensity, fat was the preferred energy source. The results show that 33 percent of calories were burned from fat while running, compared to 40 percent when walking at a 12 percent incline. Although participants burned the same number of calories, Incline Walking is seven percent more effective for fat burning than running, according to this study.

The downside is that the 12-3-30 workout is more time-consuming because you burn calories more slowly overall than when jogging at your own pace, which is usually over five kilometers per hour. So, to burn as many calories as jogging, you have to walk longer.

In response to a FITBOOK inquiry, Michael Wong, Assistant Professor-in-Residence of Kinesiology & Nutrition Sciences at the University of Nevada, summarized the findings as follows: “On average, the same amount of calories was reached about six minutes faster through jogging. Interestingly, the 12-3-30 showed about eight percent higher use of fat as an energy source compared to jogging.” The researcher emphasizes that 12-3-30 training like Incline Walking is easy to implement, especially for previously inactive people. However, he also wanted to avoid creating false hopes about walking as a miracle weight-loss method and therefore stressed: “Nevertheless, the total number of calories burned remains the decisive factor for fat and weight loss, not the ratio of fat to carbohydrate consumption in a single workout.”

How Better Fat Burning Occurs

The less intensive training method of Incline Walking provides better results than more intensive jogging–albeit with a higher time investment. Personal trainer Jörn Giersberg summed up the principle for us as follows: “When you move slower and longer, you are more likely to tap into the fat metabolism, or fat oxidation, than with more intensive movement. As soon as you become more intense, move faster, have a higher incline, etc., you switch to carbohydrate metabolism for energy production.”

Endurance training at lower intensity is also called Zone 2 training. This involves running or walking for a longer period with a relatively low heart rate. Specifically, you should train at 60 to 70 percent of your maximum heart rate (HRmax). To determine this precisely, you must first calculate your HRmax. We explained how to do this in a previous FITBOOK article.

However, there is also a simple rule of thumb: If you can talk to a training partner while running without getting out of breath, you are likely in Zone 2. This can also be well assessed in other sports such as swimming. As long as the effort feels easy and you feel like you could continue for hours, it is likely Zone 2 training. It should feel like a “sweet spot” between effort and relaxation. To benefit from fat burning, the training should last at least 30 minutes.

Our expert Enrico Zessin recommends 45 to 60 minutes (or more) of Zone 2 training two to three times a week.

Can the Findings Be Applied to Older and Overweight People?

The focus of this study was on young, normal-weight individuals. Therefore, the findings cannot be generalized to other target groups. Wong also confirmed this to us. However, he can imagine that 12-3-30 training could be a good exercise option for older and overweight people: “One possible advantage of 12-3-30 over jogging is that there is no flight phase where the body is in the air. In 12-3-30, one foot is always on the treadmill, which means less impact on the ankles, knees, and hips. This can be beneficial for people with joint pain caused by overweight or age-related conditions such as osteoarthritis.”

He added a caveat: “Nevertheless, untrained older adults or overweight or obese individuals might find 12-3-30 very challenging. In such cases, it would be sensible to adjust speed, incline, or duration. A possible starting point could be four kilometers per hour at a six percent incline for 15 to 20 minutes–with gradual increases over time. This corresponds to the principle of progressive overload, which allows the body to adapt while minimizing the risk of injury.”

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Study Limitations and Outlook

“The main limitation of our study is the relatively homogeneous participant group: healthy, physically active college students. This limits the applicability to other populations–such as older people, physically inactive individuals, or those with chronic conditions,” Wong explained in response to a FITBOOK inquiry and suggested: “Future studies should investigate how different target groups respond both metabolically and subjectively to the 12-3-30. A direct comparison with other popular training methods such as high-intensity interval training (HIIT), strength training, or new fitness trends would also be insightful–not only in terms of calorie consumption but also regarding long-term effects on fitness, weight regulation, and training adherence.”