Ketone Supplements May Worsen Performance

A study in trained endurance athletes suggests that ketone supplementation may worsen performance.

The cyclists produced about 2% less power after drinking the ketone beverage than the placebo, which would translate into a significantly slower race time, according to a new study published in the International Journal of Sport Nutrition and Exercise Metabolism.

Typically, the body uses blood glucose to produce energy. When there is not enough glucose, the body breaks down fat for energy instead. This results in the liver producing acids called ketones, which can serve as fuels for the brain and muscles.

Ketones are considered an alternative fuel source during exercise or potentially alter the utilization of other primary fuels such as carbohydrates and fats, enhancing endurance capacity.

A high-fat, very low-carbohydrate ketogenic diet is very restrictive and hard to follow long term. Some people choose ketone supplements to speed up that process without having to rely on a strict diet.

Previous findings on the effects of ketone supplements are conflicting. While some studies suggest it can improve performance, others indicate ketones have no impact or can even worsen the results.

Researchers at McMaster University recruited 23 well-trained endurance athletes who cycled five or more hours per week. They were selected because their athletic performance is consistent from day to day. Although the experiment was conducted in a lab, it stimulated race conditions, and the participants prepared as they usually would for a cycling competition.

Each participant completed two trials that differed only in the drink provided before they completed a 20-minute cycling time trial that closely predicts 40-km race performance. The drinks contained either a ketone supplement or a similar-tasting placebo.

"The main observation from this study was that the speed that the cyclists could sustain during the test was lower after drinking the ketone supplement compared to the placebo," says Devin McCarthy, lead author of the study and graduate student in the Department of Kinesiology at McMaster.

The riders produced about 2% less power after drinking the ketone beverage than the placebo, and their heart rates were also lower, but it did not ease the ride. The findings are consistent with the previous study indicating that ketone supplements may increase cardiorespiratory stress during exercise.

Nevertheless, ketone supplements are associated with some beneficial effects. A 2019 study by the same research team suggested that taking ketone supplements may help to prevent performance decrements caused by the catabolic state. Characterized by the loss of fat and muscle, the catabolic state occurs in athletes who constantly increase their training load.

While ketone supplements worsened performance in the small study, further research is needed to make recommendations about its sporting uses.