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Low carbohydrate, high fat diet impairs exercise economy and negates the performance benefit from intensified training in elite race walkers
Author(s) -
Burke Louise M.,
Ross Megan L.,
GarvicanLewis Laura A.,
Welvaert Marijke,
Heikura Ida A.,
Forbes Sara G.,
Mirtschin Joanne G.,
Cato Louise E.,
Strobel Nicki,
Sharma Avish P.,
Hawley John A.
Publication year - 2017
Publication title -
the journal of physiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.802
H-Index - 240
eISSN - 1469-7793
pISSN - 0022-3751
DOI - 10.1113/jp273230
Subject(s) - carbohydrate , ketogenic diet , endurance training , low carbohydrate , zoology , medicine , chemistry , biology , obesity , weight loss , psychiatry , epilepsy
Key points Three weeks of intensified training and mild energy deficit in elite race walkers increases peak aerobic capacity independent of dietary support. Adaptation to a ketogenic low carbohydrate, high fat (LCHF) diet markedly increases rates of whole‐body fat oxidation during exercise in race walkers over a range of exercise intensities. The increased rates of fat oxidation result in reduced economy (increased oxygen demand for a given speed) at velocities that translate to real‐life race performance in elite race walkers. In contrast to training with diets providing chronic or periodised high carbohydrate availability, adaptation to an LCHF diet impairs performance in elite endurance athletes despite a significant improvement in peak aerobic capacity.Abstract We investigated the effects of adaptation to a ketogenic low carbohydrate (CHO), high fat diet (LCHF) during 3 weeks of intensified training on metabolism and performance of world‐class endurance athletes. We controlled three isoenergetic diets in elite race walkers: high CHO availability (g kg −1 day −1 : 8.6 CHO, 2.1 protein, 1.2 fat) consumed before, during and after training (HCHO, n = 9); identical macronutrient intake, periodised within or between days to alternate between low and high CHO availability (PCHO, n = 10); LCHF (< 50 g day −1 CHO; 78% energy as fat; 2.1 g kg −1 day −1 protein; LCHF, n = 10). Post‐intervention,V ̇O 2 peakduring race walking increased in all groups ( P < 0.001, 90% CI: 2.55, 5.20%). LCHF was associated with markedly increased rates of whole‐body fat oxidation, attaining peak rates of 1.57 ± 0.32 g min −1 during 2 h of walking at ∼80%V ̇O 2 peak. However, LCHF also increased the oxygen (O 2 ) cost of race walking at velocities relevant to real‐life race performance: O 2 uptake (expressed as a percentage of newV ̇O 2 peak) at a speed approximating 20 km race pace was reduced in HCHO and PCHO (90% CI: −7.047, −2.55 and −5.18, −0.86, respectively), but was maintained at pre‐intervention levels in LCHF. HCHO and PCHO groups improved times for 10 km race walk: 6.6% (90% CI: 4.1, 9.1%) and 5.3% (3.4, 7.2%), with no improvement (−1.6% (−8.5, 5.3%)) for the LCHF group. In contrast to training with diets providing chronic or periodised high‐CHO availability, and despite a significant improvement inV ̇O 2 peak, adaptation to the topical LCHF diet negated performance benefits in elite endurance athletes, in part due to reduced exercise economy.