Ketone ester supplementation blunts overreaching symptoms during endurance training overload

Fit male subjects did two daily training sessions (6 days per week for 3 weeks) while receiving either ketone ester (n = 9) or a control drink (n = 9) after each session. Sustainable training load in week 3 and power output in the final 30 minutes of a 2-hour standardized endurance session were 15 percent higher with ketone ester than control (both P < 0.05). Ketone ester inhibited the training-induced rise in nocturnal adrenaline and noradrenaline excretion and blunted the decreases in resting, submaximal and maximal heart rate. Energy balance turned negative in the control group (-2135 kJ/day) but not in the ketone ester group (+198 kJ/day), and growth differentiation factor 15 rose about 2-fold more in the control group.