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  • ‘From the lab’ HIT effects on body composition and abdominal fat loss

    High intensity training (HIT) has often been reported in gyms throughout the land as a superior way to reduce whole-body and abdominal fat. A recent study from scientists at the Graduate School of Physical Education, Kyung Hee University provided data to support this notion and further elucidate the role of HIT on improving body composition.

    HIT refers to a number of short bursts of intense exercise that are completed in relatively quick succession. It has become a popular mode of training in recent years, most notably because many view it as an effective method for improving fitness in a relatively short space of time. It has also been purported as an efficient means of burning fat – a claim which has percolated on scientists for years. The majority of research shows that it is the total amount of exercise and not the mode or intensity that best reflects total fat loss. However, recent research opposes this; proposing that HIT has a greater fat burning effect than other forms of training i.e. low intensity training (LIT). Take for instance a study by Coker et al. (2009) who found that 12 weeks of HIT significantly reduced visceral fat when compared with LIT. A study by Nicklas et al. (2009) and another by Irving et al. (2009) yielded similar results, however all failed to underpin a precise mechanism through which this effect occurred.

    This intrigued the researchers at Kyung Hee University who, determined to see for themselves, recruited twenty-two untrained middle-aged individuals and split them into three groups: control, low-intensity (LI), and high-intensity (HI). They then asked the subjects to perform 14 weeks of training at an intensity representative of the group they were assigned to (LI = 50% maximal oxygen consumption; HI = 70% maximal oxygen consumption) with the volume of exercise calculated relative to kilograms of body weight.

    The scientists demonstrated that HI was the most beneficial form of training for improving body composition. HI significantly reduced:
    • Body weight by 4.3% vs. control 1.6% vs. LI 2.5 %
    • Hip circumference by 3.6% vs. control 1.6% vs. LI 2.8%
    • Waist circumference by 4.6% vs. control 1.2% vs. LI 2.5%
    • % body fat also reduced by 5.1% vs. control 0.6% vs. LI 0.6%, however this failed to reach statistical significance (albeit very close!).

    On the contrary, LI only showed a significant decrease in hip circumference (just!) whereas cardiorespiratory fitness was enhanced by similar amounts in both LI and HI conditions - indicating that HIT is just as good as LI for improving fitness levels and is rather affected by the total energy cost of activities.

    The precise mechanisms underpinning the above effects failed to be determined in the present study, most notably because the sample size employed was too small to detect any statistical significance in blood markers and inflammatory proteins. The merits of this research are that it was a well controlled and completely randomised study – thereby giving the researchers confidence that the exercise training programme was implemented appropriately. However, this study also has its limitations. Firstly, the study only employed female, middle-aged over-weight or obese Korean females thereby making extrapolation of the results to the general population difficult – would we see the same effect in a 21 year old male elite athlete and/or a 70 year old sedentary female? Secondly, both daily dietary intake and energy expenditure were not monitored throughout the intervention period. This means that factors such as self-motivational differences between groups may have compromised results – did those in the HI group perform more physical activity and impose additional dietary restriction in between testing bouts? Readers are thus asked to be cognisant of these limitations. Nevertheless, the data provided in this study offers support to the findings of previous research and provides a good model for further research to probe the residency of HIT in the hierarchy of fat loss training regimes.

    Lee, M. G., Park, K. S., Kim, D. U., Choi, S. M., & Kim, H. J. (2012). Effects of high-intensity exercise training on body composition, abdominal fat loss, and cardiorespiratory fitness in middle-aged Korean females. Applied Physiology, Nutrition, and Metabolism, 37, 1019-1027.
    Coker, R. H., Williams, R. H., Kortebein, P. M., Sullivan, D. H., & Evans, W. J. (2009). Influence of exercise intensity on abdominal fat and adiponectin in elderly adults. Metabolic Syndrome and Related Disorders, 7, 363-368.
    Irving, B. A., Weltman, J. Y., Patrie, J. T., Davis, C. K., Brock, D. W., Swift, D. et al. (2009). Effects of exercise training intensity on nocturnal growth hormone secretion in obese adults with the metabolic syndrome. Journal of Clinical Endocrinology and Metabolism, 94, 1979-1986.
    Niklas, B. J., Wang, X., You, T., Lyles, M. F., Demons, J., Easter, L. et al. (2009). Effect of exercise intensity on abdominal fat loss during calorie restriction in overweight and obese postmenopausal women: a randomised control trial. American Journal of Clinical Nutrition, 89, 1043-1052.
    Comments 1 Comment
    1. k.jacko's Avatar
      Err....so there 'appears' to be evidence of HIT being beneficial for fitness and fat-burning, but they don't know why and the study isn't conclusive.
      I wonder whether this article will only serve to add confusion to the debate.

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