Athletes who drop carbs cold turkey suddenly suck. It is known.
But with a smidge of stick-to-it-iveness, performance completely recovers, in virtually every. measurable. aspect.
This was shown years and years ago, in a seminal study by Drs Phinney, Bistrian, Evans, Gervino, and Blackburn.
The human metabolic response to chronic ketosis without caloric restriction: preservation of submaximal exercise capability with reduced carbohydrate oxidation (1983)
Normally, fatty acids fuel low intensity exercise and carbs fuel high. This is because high intensity exercise requires a high rate of ATP production, and glycogen to lactate generates ATP faster than a speeding bullet. This is what makes power. Getting ATP from fatty acids is like draining maple syrup from trees [at first].
However, go low carb for long enough and the syrup begins to flow like water. I lack the time to show what “long enough” entails, but 4 out of 5 studies on low carb diets and performance that only last a few days will show this. Ketoadaptation takes time; ~3 weeks.