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Original Research ARTICLE Provisionally accepted The full-text will be published soon. Notify me

Front. Physiol. | doi: 10.3389/fphys.2019.00912

Effects of a 12-week very-low carbohydrate high-fat diet on maximal aerobic capacity, high-intensity intermittent exercise, and cardiac autonomic regulation: non-randomized parallel-group study

  • 1University of Ostrava, Czechia
  • 2Auckland University of Technology, New Zealand
  • 3University of Graz, Austria

Purpose: The aim of this non-randomized parallel group study was to examine the 12-week effects of a very low-carbohydrate high-fat diet (VLCHF) on maximal cardiorespiratory capacity, high-intensity interval training (HIIT) performance and cardiac autonomic regulation.
Methods: Twenty-four recreationally trained participants allocated to either a VLCHF (N=12) or a habitual diet (HD; N=12) group completed 12 weeks of a diet and exercise (VLCHF) or an exercise only intervention (HD). Maximal graded exercise tests (GXT) were performed at baseline, after 4, 8 and 12 weeks. A supervised HIIT session and the 30-15 Intermittent Fitness Test (30-15IFT) were conducted once a week.
Results: Total time to exhaustion (TTE) in both GXT and 30-15IFT largely increased in both VLCHF (p = 0.005, BF10 = 11.30 and p = <0.001, BF10 = >100, respectively) and HD (p = 0.018, BF10 = 3.87 and p = <0.001, BF10 = >100, respectively) groups after 12 weeks. Absolute maximal oxygen uptake (V ̇O2max) was not changed in both groups but relative V ̇O2max increased in VLCHF in concert with reductions body mass (66.7±10.2 to 63.1±8.5 kg). Cardiac autonomic regulation did not reveal any between-group differences after 12 weeks. VLCHF diet induced an increase in β-hydroxybutyrate, which tended to normalize during the intervention period.
Conclusions: The 12-week VLCHF diet did not impair high-intensity continuous or intermittent exercise lasting up to 25 min, nor did it impair maximal cardiorespiratory performance or autonomic nervous system activity.

Keywords: nutritional ketosis, Graded exercise test, 30-15 intermittent fitness test, beta-hydroxybutyrate, Heart rate variability

Received: 08 Apr 2019; Accepted: 03 Jul 2019.

Edited by:

Jun Sugawara, National Institute of Advanced Industrial Science and Technology (AIST), Japan

Reviewed by:

Jonathan P. Little, University of British Columbia, Canada
Carl J. Lavie, Ochsner Medical Center, United States  

Copyright: © 2019 Dostal, Plews, Hofmann, Laursen and Cipryan. This is an open-access article distributed under the terms of the Creative Commons Attribution License (CC BY). The use, distribution or reproduction in other forums is permitted, provided the original author(s) and the copyright owner(s) are credited and that the original publication in this journal is cited, in accordance with accepted academic practice. No use, distribution or reproduction is permitted which does not comply with these terms.

* Correspondence: Dr. Lukas Cipryan, University of Ostrava, Ostrava, Czechia, lukas.cipryan@osu.cz