Burke et al. 2017, LCHF diet impairs exercise economy in elite race walkers

J Physiol 595(9):2785-2807, DOI 10.1113/JP273230. Three weeks of intensified training in elite race walkers on high-carbohydrate, periodised-carbohydrate, or ketogenic LCHF diets. LCHF increased fat oxidation approximately 2.6-fold (from roughly 0.6 to 1.57 g/min) but raised the oxygen cost of exercise (impaired economy) and was the only group not to improve a 10 km race walk, despite the training. The high-carbohydrate and periodised groups improved markedly. The decisive evidence that keto adaptation hurts race-intensity performance. Strong.