The Pre-Workout Supplement You Should Avoid

The ketogenic diet is a popular fad diet that gained popularity for its purported ability to help its followers lose weight and achieve mental clarity. Several years ago, it also garnered support in the athletic community as a way to increase performance, particularly in endurance situations. This led to it being used as a pre-workout supplement with the goal of achieving better performance. New research published in the International Journal of Sport Nutrition and Exercise Metabolism, however, suggests the opposite—that ketone supplementation might actually worsen performance.





What Are Ketones?

Let’s start with the basics: Ketones are products created by the body when it doesn’t have enough glucose to burn for energy. Like a well-oiled machine, carbohydrates are broken down in the body into glucose. Glucose is then used as the body’s primary—and preferred—source of energy. The brain particularly likes glucose. When glucose stores diminish, the body begins breaking down fat for energy, leading to a state of ketosis.



What Is Ketosis?

In a nutshell, ketosis is a metabolic state that your body goes into when it uses fat as its main source of fuel. Ketosis can be induced by dietary changes, like fasting or eating a low-carbohydrate diet, or via ketone supplementation. Ketone supplements, in the form of powders, liquids, capsules and so on, contain a type of ketone known as beta-hydroxybutyrate, otherwise known as BHB.


BHB is a ketone that is naturally produced by the liver when the body’s supply of glucose is too low. BHB supplements were manufactured to provide the body with an external source of ketones, even if a person wasn’t eating a low-carbohydrate diet. Maintaining a state of ketosis is what is suggested to lead to weight loss. And, for a myriad of reasons like having to adhere to a strict low-carb diet, maintaining ketosis is challenging. And it can lead to some negative side effects.


Ketone supplements, in that regard, have been thought to provide a “loophole” for athletes who typically would not be eating a low-carbohydrate diet. Using this strategy, athletes could still eat a balanced diet and use the supplements to get into ketosis, giving the body access to an additional source of fuel. The idea is that the body would be able to switch between fats and carbs as its energy source the same ways as a hybrid car engine can switch between gas and electricity.



What Did This Exercise Study Find?

Researchers from McMaster University enlisted highly-trained endurance athletes who cycled at least five or more hours weekly and whose “athletic performance [was] consistent from day to day,” according to a press release in ScienceDaily. The research was structured as a triple-blind study, where neither the participants, the researchers who interacted with the participants, or the researchers who did the data analysis knew whether the ketone supplement or the placebo was provided, ensuring a significantly lower likelihood of bias affecting the outcome.


Participants were required to commit to 4 lab visits. First, to assess the highest amount of oxygen consumed at peak exercise (VO2 Peak), then for a familiarization trial where they learned what the process would be like, and finally for the 2 experimental phases. Participants were asked to maintain their regular nutrition and exercise habits throughout the study and to prepare for a cycling competition as they normally would.


The experiment itself had participants engaged in two separate in-lab cycling exercises that were 7 days apart, structured to mimic race conditions. Each separate “race” accounted for other distinct variables that could have introduced bias, like bike handlebar and seat configuration as well as fan speed and location. They even accounted for the energy changes that could have affected female participants at different phases of their menstrual cycles and ensured that the two experimental races were performed in the same phase of their cycle. The only difference between each race was that the “drinks contained either a ketone supplement or a similar-tasting placebo.”


After ingesting the supplement, participants rested for thirty minutes and had their blood drawn to determine ketone, glucose, lactate, oxygen and pH levels of the blood. Then they did a 15-minute warm-up of their choosing, followed by a 20-minute timed trial which is strongly correlated with their overall cycling ability at a high intensity level. The only feedback provided to participants was how much time had elapsed in their “race”.



So, Were the Ketones Helpful?

As a reminder, BHBs are the ketone bodies that are both produced by our livers when glucose levels are low and can be synthetically manufactured into supplements to put consumers into a state of ketosis. Previous research in the Journal of Phisiology suggested that taking a ketone supplement could enhance athletic performance if the exercise was performed in a way that led to a specific BHB concentration of 1–3 mM. In this study, participants’ BHB levels were around 2 mM, which would have suggested higher performance. But that wasn’t the case at all. The main finding from the study was that the speed participants could sustain during the test was actually lower after drinking the ketone supplement, even when compared to the placebo.


Researchers think this may be due to how ketone ingestion affect pH balance of the blood, heart rate and how tired the cyclists felt during the exercise. It is still not clear how the ketone dose and the corresponding rise in BHBs would affect performance in other endurance tests that require longer exercises at a moderate to high intensity level.



The Bottom Line

More research is needed to fully understand how the body reacts to taking ketone supplements and how these reactions can changes in a person’s ability to exercise. But for now, it’s safe to say that it’s probably not going to improve your workout and it might even make it worse! Instead, focus on fueling your body with whole foods before, during and after a workout to get the most science-backed bang for your buck.

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