High intensity intermittent exercise helps shift fat and brings many other benefits

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A few weeks back I wrote about a study regarding what is often termed ‘high intensity intermittent exercise’ (HIIE). As it names suggests, this form of activity involves blasts of explosive exercise (such as sprinting or cycling) interspersed with periods of much less intense effort. The study I wrote about revealed HIIE to improve running speed in relatively fit individuals, though I used the blog post to share other evidence which suggests that this form of exercise can bring considerable improvements in terms of fat loss and insulin functioning (improved insulin sensitivity). What is more, the benefits of this form of exercise seem to generally exceed those of ‘steady state’ exercise such as running at a continuous speed.

Since I wrote that blog post, another study on HIIE has been published [1]. The target participants here were young (average age 25), overweight (average body mass index 28/29) men. The men were divided randomly into two groups. One group were not instructed on exercise (sedentary) and served as the ‘control’ or comparison group. The other group undertook a HIIE regime over 12 weeks.

Each session was made up of the following exercise:

5 minutes warm up on a stationary bicycle
20 repetitions of 8 seconds sprinting followed by 12 seconds of easy peddling (overall intensity was about 90 of maximal output)
5 minutes warm down on the bicycle

The sessions were performed 3 times a week.

The HIIE induced a number of significant changes including:

  • weight loss (average loss 1.5 kg)
  • fat loss (average loss 2.0 kg)
  • a reduction in ‘visceral’ fat (fat found in and around the organs that is particularly strongly linked with chronic diseases such as heart disease and type 2 diabetes)
  • a reduction in waist circumference
  • an increase in fat-free mass (mainly muscle)
  • increased fitness
  • increased power output
  • reduced carbohydrate metabolism
  • increased fat metabolism (average increase of 13 per cent)

No significant changes were seem in terms of measurements such as blood glucose levels, blood fat levels, measure of insulin sensitivity and resting metabolic rate.

Overall, it appears that HIIE in this group of young men brought significant benefits in a range of parameters that one would expect would translate into better health and relative protection from chronic disease. I find the fact that there seemed to be a shift from carbohydrate to fat oxidation interesting, but there is a commonly-held belief that lower intensity activity is better for fat burning while more intense activity burns just carbohydrate. This could lead some to conclude that high intensity exercise might not be so good for ‘fat burning’. Actually, this study suggests that this is not true, and adds to other evidence we have which has found HIIE to be generally superior to steady state, less intense activity in terms of fat loss.


1. M. Heydari, et al. The Effect of High-Intensity Intermittent Exercise on Body Composition of Overweight Young Males. Journal of Obesity Volume 2012;1-8 doi:10.1155/2012/48046

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