This is from the low carb skool group - where everyone is lapping it up as usual I can't be arsed posting much on there, because there is never any comeback or detailed questioning of anything. So here is the counter Corrections worth making. A glucose-fed individual already oxidises fat continuously — at rest and at low intensity, β-oxidation supplies the majority of substrate. Nobody is "locked into" glucose. CPT-1 activity, mitochondrial density and fatty acid transport are constitutively present. Keto-adaptation raises the rate and shifts the crossover point upward. It does not enable a pathway that was absent. On glycogen: the FASTER study found keto-adapted athletes had similar resting muscle glycogen to high-carbohydrate athletes — not higher (Volek et al., 2016). Utilisation and repletion patterns were comparable across a 180-minute run. Maintaining normal concentrations on ~82 g carbohydrate per day is the genuinely notable finding. "Higher" overstates it. Third point: metabolic flexibility means efficient utilisation of either substrate as demand dictates — including rapid glycolytic flux at high intensity. Sustained ketogenic adaptation can attenuate pyruvate dehydrogenase activity and blunt that capacity. What he is describing is unidirectional fat-adaptation, which is a different thing. Terminology. "Glycolysis in reverse" is wrong. Gluconeogenesis bypasses three irreversible glycolytic steps using distinct enzymes — pyruvate carboxylase, PEPCK, fructose-1,6-bisphosphatase, glucose-6-phosphatase. "Twelve weeks minimum for full enzymatic adaptation" is not an established threshold. Reported timelines span weeks to months with wide inter-individual variation. Volek, J. S., Freidenreich, D. J., Saenz, C., Kunces, L. J., Creighton, B. C., Bartley, J. M., . . . Phinney, S. D. (2016). Metabolic characteristics of keto-adapted ultra-endurance runners. Metabolism, 65(3), 100–110.