Crisis of confidence averted: Impairment of exercise economy and performance in elite race walkers by ketogenic low carbohydrate, high fat (LCHF) diet is reproducible.
Study Goal
The researchers aimed to compare the effects of a ketogenic low-carbohydrate, high-fat diet (LCHF) on performance and exercise economy in elite endurance athletes, including any "carryover" effects after restoring carbohydrate availability.
Results Summary
The LCHF diet increased fat oxidation but impaired exercise economy and performance in sustained high-intensity race walking, with no superior rebound performance after restoring carbohydrate availability. High carbohydrate diets (HCHO and PCHO) showed better performance outcomes.
Population
Elite male and female race walkers.
Effective Dosage
LCHF: <50 g∙d⁻¹ CHO, 78% energy as fat, 2.1 g∙kg⁻¹∙d⁻¹ protein.
Duration
25 days of supervised training on the diet, followed by 2.5 weeks of HCHO restoration.
Interactions
None mentioned
| Intervention | Direction | Endpoint | Population | Dosage | Impact | Claim # |
|---|---|---|---|---|---|---|
intensified training on a ketogenic low-carbohydrate (CHO), high-fat diet (LCHF) | increase | VO2peak (ml∙kg-1∙min-1) | elite male and female race walkers | - | increased | #1 |
intensified training on a ketogenic low-carbohydrate (CHO), high-fat diet (LCHF) | increase | whole-body fat oxidation | elite male and female race walkers | from 0.6 g∙min-1 to 1.3 g∙min-1 | markedly increased | #2 |
intensified training on a ketogenic low-carbohydrate (CHO), high-fat diet (LCHF) | increase | the oxygen cost of walking at race-relevant velocities | elite male and female race walkers | - | increased | #3 |
High CHO availability (HCHO) diet | increase | 10,000 m performance | elite male and female race walkers | 4.8% or 134 s | improved | #4 |
periodised CHO (PCHO) diet | increase | 10,000 m performance | elite male and female race walkers | 2.2%, 61 s | trend for a faster time | #5 |
ketogenic low-carbohydrate (CHO), high-fat diet (LCHF) | decrease | 10,000 m performance | elite male and female race walkers | 2.3%, -86 s | were slower | #6 |
LCHF intervention followed by 2.5 wk of HCHO restoration and taper | no change | "rebound" performance over 20 km | a cohort (n = 19) of elite race walkers | - | no evidence of superior | #7 |
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.