Exogenous Ketone Supplementation Impairs High-Intensity Performance (*Study)

Exogenous ketone supplementation decreases high-intensity exercise performance by 7% according to a recently published study.

Researchers at the School of Health and Exercise Sciences at the University of British Columbia had fasted, recreationally active, test subjects consume either 0.3 g/kg β-OHB ketone salts or a placebo, then complete two bouts of high-intensity exercise consisting of a warmup at 30%, 60%, and 90% of ventilatory threshold followed by a 150-kJ cycling time-trial.

Respiratory Exchange Ratio was lower at 30% and 60% with ketone use, as was ventilatory threshold with ketones compared to control condition. Exercise intensity was lower in the ketone-supplemented group and it took them longer to burn the same amount of calories when compared to placebo ingestion.

Average time-trial power output was ∼7% lower with ketone supplementation.

If you use ketone supplements before Airdyne or Concept2 calorie sprints, expect them to take longer. If you use ketone supplements before timed cardio sessions, expect to burn less calories in a given session. If you use ketone supplements before high-intensity competition — stop.

Total fat oxidation was greater with ketone use — but here’s where things get a bit confusing if you’re someone who does timed cardio (i.e. half an hour on the treadmill or stairmaster). This study used total calories burned as the end point of the time trial, meaning both the ketone and placebo group burned the same amount of calories (but it took the ketone group longer).

You’re burning a higher percentage of your energy from fat with ketone use, but you’re also using less energy. So you’re burning a higher percentage of a lower number — which intuitively isn’t the best tradeoff.

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