Another study on exercise and ketogenic diets (Journal of Physiology, Volume 595, Issue 9, 1 May 2017, Pages 2785-2807. Low carbohydrate, high fat diet impairs exercise economy and negates the performance benefit from intensified training in elite race walkers. Louise M. Burke Megan L. Ross Laura A. Garvican‐Lewis Marijke Welvaert Ida A. Heikura Sara G. Forbes Joanne G. Mirtschin Louise E. Cato Nicki Strobel Avish P. Sharma John A. Hawley.).
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.
Let’s ignore the shortness of the study for the sake of argument. The trade-off here is that when you burn more fat you require more oxygen for that burning.
…CHO as a substrate for muscle metabolism by virtue of an approx 8% higher energy yield per litre of oxygen (O2) consumed when CHO was the primary fuel oxidised.
This might explain the higher heart rates reported while exercising on Low Carb diets (Using Body Fat for Energy). I’ve seen this myself.
I am convinced there are exercise domains that Low Carb does great in but some it does not do as well. I think CrossFit is one of these. These are glycolytic sports but unless you are a world-class athlete does it really matter? And is it worth your health to compete at some of these elite levels?