Fat Burning Benefits of High Intensity Interval Training (HIIT)


Author: Kate Headrick, Master Trainer’s Academy CPT Student

The United States has seen a dramatic rise in obesity over the past few decades and research has shown obesity’s alarming effects on the body. Exercise is a top recommendation, but with the demands of our busy lives, finding time to exercise can be difficult. High intensity interval training (HIIT) has emerged as a time saving strategy to reduce body fat and improve cardiovascular function, while reducing the time required for exercise. HIIT protocols involve short bursts of maximal effort, followed by longer periods of recovery, which is repeated for a prescribed number of repetitions. HIIT is an effective method for fat reduction and a valid strategy for reducing metabolic risk factors in overweight and obese populations.

HIIT training requires very little time and for that reason is becoming more popular. According to Zang, Tong, Qui, Nie, and He (2017), HIIT cardio of just 28 minutes 3 times per week was just as effective in burning abdominal fat as 60 minutes of moderate intensity steady state of the same frequency (p 3). Previous protocols have always linked volume and fat reduction increasing together in a linear fashion, relying on short periods of maximal effort followed by longer active recovery periods; and it is in these recovery periods that HIIT’s fat burning potential shines. The sheer intensity of HIIT extends our body’s excess post exercise oxygen consumption or EPOC (Trapp, Chisholm, & Boutcher, 2007). EPOC is the state in which the body’s metabolism is elevated after exercise (Clark, Lucett, McGill, Montel & Sutton, 2018)  Alahmadi (2014) found that the larger EPOC response from HIIT may have a role in elevating post-exercise fat oxidation due to increasing levels of epinephrine and norepinephrine generated during acute HIIT. It is during this extended EPOC period that fat is used as the primary energy source; and fat expenditure is correlated to the intensity of the previous exercise, making HIIT a front runner as opposed to low or moderate intensity exercise. It was also found that the elevated catecholamine levels increased overall fat oxidation during and after HIIT (Alahmadi, 2014).

HIIT is also effective for fat oxidation during exercise. A recent study performed at the College of Sports Sciences and Physical Science examined this link in obese and overweight men over a four week period. They found HIIT training improved fat oxidation by 31% in just 3 sessions per week for 4 weeks. The exact mechanism behind the fat oxidation was beyond the scope of this study, but their findings suggested that HIIT boosting the skeletal muscle’s capability to oxidize lipids, which could have an enormous impact in obese populations (Alahmadi, 2014). By improving the body’s ability to use skeletal muscle to oxidize fat we are potentially able to increase their ability to burn fat at rest and during other activities throughout the day. As trainers, this could be an incredible advantage in our tool box to help our clients achieve good health and reduce their risk of disease. Based on the information available and the data from numerous studies HIIT has proven to be a safe and effective method to burn fat. Additionally, because of the intensity of the exercise, it also improves skeletal muscles ability to metabolically adapt and extend the body’s fat burning window beyond the length of the exercise itself.  By utilizing HIIT protocols with our clients we can maximize their results and improve their quality of life.



  1. Zang, H., Tong, T.K., Qui, W., Nie, J., and He, Y. (2015). Effect of high intensity interval training protocol on abdominal fat reduction in overweight chinese women: randomized controlled trial. Kinesiology.
  2. Trapp, E. G., Chisholm, D. J., and  Boutcher, S.H. (2007). Metabolic response of trained and untrained women during high- intensity intermittent cycle exercise. Am J PhysiolRegulIntergr Comp Physiol, 293, R2370-2375.
  3. Alahmmadi, M.A. (2014) High-intensity Interval Training and Obesity. J Nov Physiother      4(2111). Doi: 10.4172/2165-7025.1000211
  4. Clark, M. A, Lucett, S. C., McGill, E., Montel, I., and Sutton, B. (Eds.) (2018). NASM essentials of personal fitness training (6th ed.). Burlington, MA: Jones & Bartlett Learning.

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