High-intensity interval training (HIIT) is worth considering if “that stubborn body fat isn’t going away”, according to a study which found that HIIT increases fat-burning more than aerobic exercise.
The study, by Professor Zeljko Pedisic and colleagues from Victoria University in Melbourne, Australia, which was published in the British Journal of Sports Medicine, pooled results from 18 controlled intervention trials on the effects of HIIT on the rate of fat-burning during exercise. The intervention trials included a total of 511 adult participants who did supervised HIIT, moderate-intensity aerobic exercise, or a non-exercising control group. The duration of exercise interventions ranged from two to 14 weeks. In almost all studies, participants engaged in three HIIT sessions per week.
What are the key findings?
A few sessions of HIIT per week will turn your body into a fat-burning “machine”. HIIT will make you start burning more fat not just during the HIIT sessions, but also during other types of physical activity, such as brisk walking, swimming and playing sports.
Fat metabolism will improve after only four weeks of HIIT, and will continue to improve with time.
After 12 weeks of HIIT, each minute of physical activity is expected to burn an additional 0.13 grams of fat. For someone who engages in 150 minutes of physical activity per week, this could lead to 10kg of additional fat burned in a decade.
Overweight individuals may expect greater increases in fat burning, compared with “normal”-weight individuals.
You could also improve fat metabolism by engaging in aerobic exercise (e.g. jogging). However, that would require a much higher time commitment, and the improvements would be smaller.
Why is this important?
These findings may help more than 2bn overweight people in the world to improve their fat metabolism and reduce weight. They may also help billions of others to prevent unwanted weight gain over time.
“According to the recent Worldwide Survey of Fitness Trends, HIIT is among the most popular types of workouts. If you are not already doing it, maybe you should give it a go,” said Pedisic.
Study details
Effects of high-intensity interval training (HIIT) and sprint interval training (SIT) on fat oxidation during exercise: a systematic review and meta-analysis
Muhammed Atakan, Yasemin Guzel, Nipun Shrestha, Sukran Kosar, Zeljko Pedisic.
Published in the British Journal of Sports Medicine on 20 July 2022
Abstract
Objective
To investigate the effects of high-intensity interval training (HIIT) and sprint interval training (SIT)
on fat oxidation during exercise (FatOx) and how
they compare with the effects of moderate-intensity continuous training (MICT).
Eligibility criteria for selecting studies
Studies using a between-group design, involving adult participants who were not trained athletes, and evaluating effects of HIIT or SIT on FatOx (vs no exercise or MICT) were included.
Results
Eighteen studies of fair-to-good quality
were included; nine comparing HIIT or SIT with no exercise and eleven comparing HIIT or SIT with MICT.
A significant pooled effect of these types of interval training on FatOx was found (mean difference in g/min (MD)=0.08; 95% confidence interval (CI) 0.04 to 0.12; p<0.001). Significant effects were found for exercise regimens lasting ≥4 weeks, and they increased with every additional week of training (β=0.01; 95% CI 0.00 to 0.02; p=0.003). HIIT and/or SIT were slightly more effective than MICT (MD=0.03; 95% CI 0.01 to 0.05; p=0.005). The effects on FatOx were larger among individuals with overweight/obesity.
Conclusion
Engaging in HIIT or SIT can improve FatOx, with larger effects expected for longer training regimens and individuals with overweight/obesity. While some effects seem small, they may be important in holistic approaches to enhance metabolic health and manage obesity.
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