A few minutes of short, intense exercise can be more effective for burning body fat than running or any other type of long-duration exercise. Don’t believe it? Let’s take a look at what science says.
Before we begin, let’s define a few types of training terms:
HIIT (High-Intensity Interval Running): HIIT protocols vary greatly from study to study. Durations range from a few seconds up to 2, 3, or 4 minutes, with 4–12 repetitions at 80–90% of maximum heart rate.
MICT (Moderate-Intensity Continuous Running): >30 minutes at a moderate intensity.
SIT (Sprint Interval Training): 4–10 repetitions × 30 seconds at maximum intensity, with 4–5 minute rests between each sprint.
REHIT (Reduced-Exertion High-Intensity Interval Training): 2–3 sprints at maximum possible intensity for 10 to 20 seconds, with 3–4 minute rests between each sprint.
This systematic review of studies analyzed the effectiveness of high-intensity running training compared to moderate-intensity running, and the authors concluded that high-intensity training (HIIT) is just as effective as moderate-intensity training. In some included studies, HIIT was even superior in reducing body weight.
It’s important to note that high-intensity workouts last on average 50% less time than moderate-intensity workouts. Therefore, HIIT is much more efficient considering the time invested. [1]
Another study showed similar results: HIIT led to similar reductions in body weight and, additionally, resulted in better cardiorespiratory fitness in a shorter period. Thus, HIIT continues to be superior. [2]
In a study with overweight women, 8-second sprints with 12-second rest intervals were compared with continuous training at 60–70% of maximum heart rate for 30 minutes. The sprint group (HIIT) saw a greater reduction in body fat percentage as well as improvements in other body measurements. [3]
The big question: which is the most effective training in a short amount of time?
A study comparing HIIT vs SIT in young women found that after 8 weeks of training, both HIIT and SIT resulted in improvements in anthropometric measures and cardiorespiratory fitness, even without changes in dietary intake. Moreover, the SIT protocol led to greater reductions than the HIIT protocol in skinfold thickness. Both protocols seem to be efficient time-saving interventions. [5]
In another meta-analysis of 18 studies comparing the effectiveness of SIT vs MICT vs HIIT for fat loss, it was concluded that practicing either HIIT or SIT can improve fat burning, with greater effects observed in longer-duration programs (>4 weeks) and in individuals with overweight/obesity. [9]
Although there are no studies comparing these two types of exercise in terms of fat loss, several studies do compare their influence on the cardiorespiratory system.
One study compared 10-second sprints with 30-second sprints and showed that the protocol of 4–6 repetitions of 10 seconds, with 2 to 4 minutes of rest, 3 times per week for just 2 weeks, can equally increase VO₂max (a measure of cardiorespiratory fitness) when compared to the 30-second sprint protocol. [6]
Another study compared REHIT and MICT in patients with diabetes and concluded that REHIT is superior to five times the volume of moderate-intensity walking in improving aerobic fitness. The same results were found in another 8-week study. [7][8]
According to scientific literature, high-intensity exercises appear to induce better cardiorespiratory responses and lead to more significant fat burning when compared to continuous, moderate-intensity running.
Following a HIIT or SIT protocol seems to be ideal for enhancing fat burning. And from an efficiency standpoint—considering that most people don’t have much time available to train—the best options are undoubtedly high-intensity protocols.
