AUTHOR=Dostal Tomas , Plews Daniel J. , Hofmann Peter , Laursen Paul B. , Cipryan Lukas 

TITLE=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

JOURNAL=Frontiers in Physiology

VOLUME=10

YEAR=2019

URL=https://www.frontiersin.org/journals/physiology/articles/10.3389/fphys.2019.00912

DOI=10.3389/fphys.2019.00912

ISSN=1664-042X

ABSTRACT=<sec><title>Purpose</title><p>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.</p></sec><sec><title>Methods</title><p>Twenty-four recreationally trained participants allocated to either a VLCHF (<italic>N</italic> = 12) or a habitual diet (HD; <italic>N</italic> = 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 (30-15<sub>IFT</sub>) were conducted once a week.</p></sec><sec><title>Results</title><p>Total time to exhaustion (TTE) in both GXT and 30-15<sub>IFT</sub><italic>largely</italic> increased in both VLCHF (<italic>p</italic> = 0.005, BF<sub>10</sub> = 11.30 and <italic>p</italic> = 0.001, BF<sub>10</sub> ≥ 100, respectively) and HD (<italic>p</italic> = 0.018, BF<sub>10</sub> = 3.87 and <italic>p</italic> = 0.001, BF<sub>10</sub> ≥ 100, respectively) groups after 12 weeks. Absolute maximal oxygen uptake (<inline-formula><mml:math id="M1" xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:mover accent="true"><mml:mi>V</mml:mi><mml:mo>˙</mml:mo></mml:mover></mml:math></inline-formula>O<sub>2max</sub>) was not changed in both groups but relative <inline-formula><mml:math id="M2" xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:mover accent="true"><mml:mi>V</mml:mi><mml:mo>˙</mml:mo></mml:mover></mml:math></inline-formula>O<sub>2max</sub> increased in VLCHF in concert with reductions in body mass (66.7 ± 10.2–63.1 ± 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.</p></sec><sec><title>Conclusion</title><p>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 (ANS) activity.</p></sec>