The Ketogenic Diet Alters Endocrine Regulation of Energy Metabolism in Ultra-Endurance Athletes

PurposeThe ketogenic diet induces a profound shift in energy metabolism from carbohydrate oxidation towards fat oxidation, both at rest and during exercise. We compared endocrine regulators of energy metabolism in keto-adapted and non-keto-adapted ultra-endurance athletes before, during, and after aerobic exercise to better understand the role of endocrine function in adaptation to a ketogenic diet (keto-adaptation). MethodsTwenty elite ultra-endurance athletes (male, age 33.5 ± 6.4 yr, BMI 22.1 ± 1.5 kg/m2, VO2max 64.5 ± 4.9 mL/kg/min) who habitually consumed a high-carbohydrate (HC, 59:14:25 % carbohydrate:protein:fat) or very-low carbohydrate (LC, 10:19:70) diet for at least 6 months ran on a treadmill for 180 min at 64% of VO2max. Glucagon, cortisol, and leptin were measured from serum collected before exercise (BL); 60 and 120 min after initiation of exercise (RUN60, RUN120); and 0, 60, and 120 min after completion of exercise (IP, P60, P120). After BL and IP, participants consumed a shake with macro...