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Impact Of Ketogenic Diet On Athletes: Current Insights

Authors McSwiney FT, Doyle L, Plews DJ, Zinn C

Received 3 July 2019

Accepted for publication 4 October 2019

Published 15 November 2019 Volume 2019:10 Pages 171—183


Checked for plagiarism Yes

Review by Single anonymous peer review

Peer reviewer comments 4

Editor who approved publication: Prof. Dr. Andreas Imhoff

Fionn T McSwiney,1,2 Lorna Doyle,3 Daniel J Plews,4 Caryn Zinn4

1School of Health and Human Performance, Dublin City University, Dublin, Ireland; 2Setanta College, Thurlus, Tipperary, Ireland; 3Department of Sport and Exercise Science, Waterford Institute of Technology, Waterford, Ireland; 4Sports Performance Research Institute New Zealand (SPRINZ), Auckland University of Technology, Auckland, New Zealand

Correspondence: Caryn Zinn
AUT University, Sports Performance Research Institute New Zealand (Mail code P-1), Private Bag 92006, Auckland 1142, New Zealand
Tel +64 9 921 9999
Fax +64 9 921 9960

Abstract: The impact of a ketogenic diet (KD) (<50 g/d carbohydrate, >75% fat) on athletic performance has sparked much interest and self-experimentation in the past 3–4 years. Evidence shows 3–4-week adaptations to a KD in endurance-trained athletes were associated with maintenance of moderate (46–63% VO2max) and vigorous intensity (64–90% VO2max) endurance exercise, while at intensities >70% VO2max, increases in fat oxidation were associated with decreased economy (increased oxygen consumption), and in some cases, increased ratings of perceived exertion and heart rate. Two investigations in recreationally active endurance athletes noted no vigorous intensity exercise decrement following 3- and 12-week adaptations. Moderate (70–85% one repetition maximum) and near-maximal to maximal intensity (>85% 1RM) strength performance experienced no decrement following a 3-12-week KD adaptation. Beneficial effects were noted for 2000 m sprint and critical power test completed for short duration at vigorous intensity, while two additional tests noted no decrement. For sprint, near-maximal exercise (>91% VO2max), benefit of the KD was observed for six-second sprint, while no decrement in performance was noted for two additional maximal tests. When protein is equated (grams per kilogram), one investigation noted no decrement in muscle hypertrophy, while one noted a decrement. One investigation with matched protein noted the KD group lost more body fat. In conclusion, moderate-to-vigorous intensity exercise experiences no decrement following adaptation to a KD. Decreases in exercise economy are observed >70% VO2max in trained endurance athletes which may negate performance within field settings. Beneficial effects of the KD during short duration vigorous, and sprint bouts of exercises are often confounded by greater weight loss in the KD group. With more athletes pursuing carbohydrate-restricted diets (moderate and strict (KD)) for their proposed health benefits, more work is needed in the area to address both performance and health outcomes.

Keywords: keto-adaptation, performance, endurance, strength, high intensity, low carbohydrate

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