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• Letter to the editor
  Matthew A Hollings, Jeff S Coombes, Yorgi Mavros, Shelley E Keating and Maria A Fiatarone Singh
  Published on: 3 June 2019
• Response to 'A few unanswered questions'
  Ricardo B Viana
  Published on: 13 May 2019
• A few unanswered questions
  Anoop Balachandran
  Published on: 29 April 2019

• Published on: 3 June 2019

  Letter to the editor

  • Matthew A Hollings, PhD Student University of Sydney
  • Other Contributors:
    • Jeff S Coombes, Professor
    • Yorgi Mavros, Lecturer
    • Shelley E Keating, NHMRC Early Career Fellow
    • Maria A Fiatarone Singh, Professor

  After careful appraisal and following our own investigations, we are concerned that the article “Is interval training the magic bullet for fat loss? A systematic review and meta-analysis comparing moderate-intensity continuous training with high-intensity interval training (HIIT)” [1] may have some data extraction and analysis errors that warrant further review by the editor and authors, and which more concerningly, may impact the original conclusions of the article.

  We were initially concerned about the reported results within the Thomas et al. paper [2], particularly the biological plausibility of a mean between-group fat-loss difference of 13.44 kg over 12 weeks. Given that the authors did not report any study-level data, we decided to investigate the effect size within this paper. However, this study [2] did not report any fat mass data, only % body fat data. Given that the authors of the review [1] reported “When studies provided insufficient data for inclusion in the meta-analysis (five studies), the corresponding authors were contacted via email to determine whether additional data could be provided; however, no corresponding authors responded.”, it is unclear how an unpublished mean difference of -13.44 kg in favour of HIIT/SIT could be presented within the fat mass analysis of this review. Furthermore, when reviewing another of the included studies [3], we found that fat mass data were reported, but not included in the current meta-analysis [1]. Given the m...

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  After careful appraisal and following our own investigations, we are concerned that the article “Is interval training the magic bullet for fat loss? A systematic review and meta-analysis comparing moderate-intensity continuous training with high-intensity interval training (HIIT)” [1] may have some data extraction and analysis errors that warrant further review by the editor and authors, and which more concerningly, may impact the original conclusions of the article.

  We were initially concerned about the reported results within the Thomas et al. paper [2], particularly the biological plausibility of a mean between-group fat-loss difference of 13.44 kg over 12 weeks. Given that the authors did not report any study-level data, we decided to investigate the effect size within this paper. However, this study [2] did not report any fat mass data, only % body fat data. Given that the authors of the review [1] reported “When studies provided insufficient data for inclusion in the meta-analysis (five studies), the corresponding authors were contacted via email to determine whether additional data could be provided; however, no corresponding authors responded.”, it is unclear how an unpublished mean difference of -13.44 kg in favour of HIIT/SIT could be presented within the fat mass analysis of this review. Furthermore, when reviewing another of the included studies [3], we found that fat mass data were reported, but not included in the current meta-analysis [1]. Given the marginal level of significance for the fat mass outcome in the review (MD, CI; -2.28, [-4.00, -0.56]), it is possible that if these data had been excluded/included the primary conclusion of this article (that HIIT training resulted in superior fat mass loss compared to moderate intensity aerobic training), may be altered.

  Additionally, upon review of the first two data points in the % body fat plot, we also have concerns regarding the calculated effect sizes. We are unable to confirm the accuracy of the calculations, given the lack of study-level data reported and the absence of effect size (ES) calculation methods in either the review article methods or the registered protocol on PROSPERO (CRD42018089427). Whilst the Thomas et al. [2] paper reported % body fat data graphically, and we acknowledge there may be some minor differences in data points depending on which graph analysis tool was used, the Trapp et al. [3] paper reported all pre- and post- mean and standard error data, so our ES and CI calculations should be identical to those in the review if the same calculation method was used. However, our calculated ES using the pooled baseline SD for ES calculation (-3.30 [-13.36, 6.76]) varied significantly from that reported by the Viana et al (-9.59 [-16.97, -2.20]). Presuming that the authors are presenting mean difference data (as suggested in their forest plot figures), there should be no disputing this value as -3.30, based solely on study-level data. Our analyses only examined data from these two studies, so we can neither verify nor refute the results presented for the remaining 34 included studies.

  Finally, we question the inclusion of one of the studies in the review. Viana et al. have included the study by Boer and Moss [4] that used 70-80% VO2peak for their moderate intensity exercise. This is outside the 40-60% VO2max ‘criteria’ for moderate intensity provided by the authors.

  In conclusion, we have grave concerns about the accuracy of the data extraction and analysis, as well as study selection in the Viana et al review [1]. We would ask the editors therefore to request clarification and transparency in the methods used to derive the statistical comparisons presented in the published review. At minimum, a published correction of the article is needed, given the likelihood that this review will be highly cited by others who do not have the time or the statistical knowledge to question the findings. However, if the conclusions of the article are in fact driven by the errors in data extraction and analysis noted above, then full retraction may be indicated.

  [1] Viana RB, Naves JPA, Coswig VS, et al Is interval training the magic bullet for fat loss? A systematic review and meta-analysis comparing moderate-intensity continuous training with high-intensity interval training (HIIT) Br J Sports Med. Published Online First: 14 February 2019.
  [2] Thomas TR, Adeniran SB, Etheridge GL. Effects of different running programs on VO2max, percent fat, and plasma lipids. Can J Appl Sport Sci 1984;9:55–62.
  [3] Trapp EG, Chisholm DJ, Freund J, et al. The effects of high-intensity intermittent exercise training on fat loss and fasting insulin levels of young women. Int J Obes 2008;32:684–91.
  [4] Boer PH , Moss SJ . Effect of continuous aerobic vs. interval training on selected anthropometrical, physiological and functional parameters of adults with Down syndrome. J Intellect Disabil Res 2016;60:322–34

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  Conflict of Interest:
  None declared.

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• Published on: 13 May 2019

  Response to 'A few unanswered questions'

  • Ricardo B Viana, Ph.D. candidate Federal University of Goiás

  Dear Dr. Anoop Balachandran

  We would like to thank you for your insightful and interesting comment.

  Regarding the first point, we presented the 28.5% to illustrate the relative difference in total absolute fat (kg) change between interventions, so the reader could have information about the relative difference between groups. We would like to highlight that it was only possible to perform this analysis using the within group changes, since the change between group analysis was showed in absolute values.

  About the second point, it was not our purpose to analyse lean body mass; however, we agree that this topic is very important for health and athletic performance purposes. This is an unanswered question and we are performing studies to test the effects of interval training on lean body mass to help shedding light in the topic.

  Best regards.

  Conflict of Interest:
  None declared.

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• Published on: 29 April 2019

  A few unanswered questions

  • Anoop Balachandran, Assistant Professor Queens College

  The study raises two questions that one of the authors might be able to help with:

  First, the authors report both within group and between group changes in body fat in the abstract. But it is unclear why the authors chose the within-group changes (28% fat loss) as the study conclusion than the between-group change.

  The within group change showed a fat loss of 0.45 kg (28%) in favor of interval training (IT), while the between-group changes showed a large difference of 2.28 kg of fat loss in favor of IT. Considering the large difference in fat loss, and some studies recommending to avoid within group differences in meta-analysis, it would be helpful if the authors could comment on this.

  Second, maintaining lean body mass (LBM) is one of the primary reasons to include exercise as part of a weight loss strategy. So it is not clear why the authors chose not to include lean body mass as one of the outcomes. It would have certainly helped the reader to make a decision regarding the choice of exercise for weight loss.

  Finally, congratulations to all the authors for asking a very relevant question!.

  Conflict of Interest:
  None declared.

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