Acute Ketogenic Diet and Ketone Ester Supplementation Impairs Race Walk Performance

Eighteen elite race walkers (15 males, 3 females) did economy tests and a 10,000 m race before and after a 5-day high-carbohydrate diet (n = 9) or a low-carbohydrate high-fat (LCHF) diet (n = 9). The LCHF group also did economy tests after 573 mg/kg ketone ester (KE), which was consumed again for the second race. LCHF increased the oxygen cost of exercise and fat oxidation, KE raised circulating ketones to a peak of 3.2 mM but did not alter oxygen consumption or respiratory exchange ratio, and race performance was impaired by about 6 percent in the LCHF group (p < 0.0001) but not in the high-carbohydrate group.