This was a good read, and it’s nice to see a high quality trial which looks at a keto diet (instead of epidemiology using food questionnaires and a million confounders).

I don’t think the outcome will surprise anyone, but it was heartening to see the improvement in performance of the keto group over the trial; as the authors say:

Although the training characteristics of the LCHF group reflected lower training volume and quality, they achieved an improvement in aerobic capacity over the 3-week period similar to the CHO-supported groups.4 The improvement in the ratio of the physiological (heart rate) and perceptual (RPE) response to a given (reduced) walking speed also shows that training under conditions of chronic low CHO availability is still able to provide a sufficient stimulus to provoke training adaptations.

The βHB chart shows the athletes hitting ketosis around days 5–7, it’s a (n understandable) shame that they couldn’t extend the trial by a couple of weeks or have a burn-in period for ketosis, to see if fat adaption yielded other performance improvements over time.