The effects of endogenously- and exogenously-induced hyperketonemia on exercise performance and adaptation

Trained endurance athletes completed 6 days of laboratory cycling while following a carbohydrate-rich control diet (n = 7), a carbohydrate-rich diet plus a ketone drink four times daily (n = 7, Ex Ket), or a ketogenic diet (n = 7, End Ket). Urinary beta-hydroxybutyrate rose about 150-fold with Ex Ket and about 650-fold with End Ket versus control. Exercise capacity was increased by 6 to 8 percent on days 1, 4 and 6 with Ex Ket, and decreased by 48 to 57 percent on all race days with End Ket. End Ket produced about a 3-fold increase in fat oxidation and higher perceived exertion, while Ex Ket was associated with blunted postprandial insulin sensitivity.