Crisis of confidence averted: Impairment of exercise economy and performance in elite race walkers by ketogenic low carbohydrate, high fat (LCHF) diet is reproducible

Louise M Burke; Avish P Sharma; Ida A Heikura; Sara F Forbes; Melissa Holloway; Alannah K A McKay; Julia L Bone; Jill J Leckey; Marijke Welvaert; Megan L Ross

doi:10.1371/journal.pone.0234027

Crisis of confidence averted: Impairment of exercise economy and performance in elite race walkers by ketogenic low carbohydrate, high fat (LCHF) diet is reproducible

PLoS One. 2020 Jun 4;15(6):e0234027. doi: 10.1371/journal.pone.0234027. eCollection 2020.

Authors

Louise M Burke^{1

2}, Avish P Sharma^{1

3}, Ida A Heikura^{1

2}, Sara F Forbes¹, Melissa Holloway¹, Alannah K A McKay^{1

4

5}, Julia L Bone^{1

2}, Jill J Leckey², Marijke Welvaert^{1

6}, Megan L Ross^{1

2}

Affiliations

¹ Australian Institute of Sport, Canberra, Australia.
² Mary MacKillop Institute for Health Research, Australian Catholic University, Melbourne, Australia.
³ Griffith Sports Physiology and Performance, School of Allied Health Sciences, Griffith University, Gold Coast, Australia.
⁴ School of Human Sciences (Exercise and Sport Science), The University of Western Australia, Crawley, WA, Australia.
⁵ Western Australian Institute of Sport, Mt Claremont, WA, Australia.
⁶ University of Canberra Research Institute for Sport and Exercise, Canberra, Australia.

Abstract

Introduction: We repeated our study of intensified training on a ketogenic low-carbohydrate (CHO), high-fat diet (LCHF) in world-class endurance athletes, with further investigation of a "carryover" effect on performance after restoring CHO availability in comparison to high or periodised CHO diets.

Methods: After Baseline testing (10,000 m IAAF-sanctioned race, aerobic capacity and submaximal walking economy) elite male and female race walkers undertook 25 d supervised training and repeat testing (Adapt) on energy-matched diets: High CHO availability (8.6 g∙kg-1∙d-1 CHO, 2.1 g∙kg-1∙d-1 protein; 1.2 g∙kg-1∙d-1 fat) including CHO before/during/after workouts (HCHO, n = 8): similar macronutrient intake periodised within/between days to manipulate low and high CHO availability at various workouts (PCHO, n = 8); and LCHF (<50 g∙d-1 CHO; 78% energy as fat; 2.1 g∙kg-1∙d-1 protein; n = 10). After Adapt, all athletes resumed HCHO for 2.5 wk before a cohort (n = 19) completed a 20 km race.

Results: All groups increased VO2peak (ml∙kg-1∙min-1) at Adapt (p = 0.02, 95%CI: [0.35-2.74]). LCHF markedly increased whole-body fat oxidation (from 0.6 g∙min-1 to 1.3 g∙min-1), but also the oxygen cost of walking at race-relevant velocities. Differences in 10,000 m performance were clear and meaningful: HCHO improved by 4.8% or 134 s (95% CI: [207 to 62 s]; p < 0.001), with a trend for a faster time (2.2%, 61 s [-18 to +144 s]; p = 0.09) in PCHO. LCHF were slower by 2.3%, -86 s ([-18 to -144 s]; p < 0.001), with no evidence of superior "rebound" performance over 20 km after 2.5 wk of HCHO restoration and taper.

Conclusion: Our previous findings of impaired exercise economy and performance of sustained high-intensity race walking following keto-adaptation in elite competitors were repeated. Furthermore, there was no detectable benefit from undertaking an LCHF intervention as a periodised strategy before a 2.5-wk race preparation/taper with high CHO availability.

Trial registration: Australia New Zealand Clinical Trial Registry: ACTRN12619000794101.

Publication types

Clinical Trial
Research Support, Non-U.S. Gov't

MeSH terms

Adaptation, Physiological
Athletes
Athletic Performance*
Diet, High-Fat*
Diet, Ketogenic*
Female
Humans
Male
Physical Conditioning, Human* / methods
Physical Endurance
Walking*

Associated data

ANZCTR/ACTRN12619000794101

Grants and funding

This study was funded by a Program Grant from the Australian Catholic University Research Funds to Professor Louise Burke (ACURF, 2017000034).