Article Review: Nutritional Ketosis in Athletes

This article brings up the discussion of ketosis’s role in sports once again, but this time through the novel method of nutritional supplementation. Ketosis is the body’s natural response to energy crisis. Until recently, people have only been able to induce ketosis by creating the CHO/caloric deficit over the course of about two days. This means that there is trigger in our body that senses these diet deficits, resulting in a switch from CHO as the primary fuel to fats and ketone bodies, a byproduct of this depleted state. This preference change happens because of an automatic effort from the body to begin to ration the valuable CHO’s used in brain function, and fight or flight type responses.

Ketosis’s energy preference seemed most suitable for endurance athletes because they want to preserve CHO to provide a final kick in their competition, as well as increasing their lactate threshold ceiling. Lactate threshold refers to the amount of lactic acid that is produced from CHO metabolism (glycolysis), and the body’s ability to buffer that lactic acid. If more lactate is accumulated than can get buffered, the body crosses the lactate threshold, either calling for a reduction in intensity to continue exercising or the muscle continues to accumulate more and more lactate until it fatigues out. The problem scientists ran into when implementing a ketosis diet in athletics was the majority of studies actually showed a decreased or no change in performance. If there would be no improvement in performance, than the added stresses of CHO/caloric deficits could not be justified.

The topic of ketosis for athletics has been reintroduced because scientists have discovered a way to increase ketone bodies through a nutritional supplement. They did this by generating an edible ketone body by transesterifying ethyl (R)-3-hydroxybutyrate with (R)-1,3-butanediol using lipase. I don’t know what that means, but it may be interesting to some. Anyways, they created this nutritional supplement called “ketone ester” (KE). This has proved to be a safe and effective way to elevate blood ketone levels (Clarke et al., 2012; Shivva et al., 2016) without the starvation diet.

This article is a review of five studies that examined nutritional ketosis in advanced to elite endurance cycling athletes. The supplemented KE was in addition to a normal diet consisting of all macronutrients (CHO, Fat, and Protein). The first study looked at blood and urine for KE concentration to understand if the body would absorb the KE or get rid of it. The cyclists ingested the KE drink prior to two hour long rides set at 40% and 75% of their maximum energy output (Wmax). The KE in the urine was found to be negligible, which is a good indication that the body is absorbing the KE, but the big finding for this study was their calculation of the contribution of the ketone bodies to the total metabolism. This study found around 30-45 minutes into cycling, ketone oxidation accounted for 16-18% of total oxygen consumption.

The bar graph on the left illustrates total metabolic contribution from this study, and the graph on the right serves as a general comparison of macronutrient contribution during different types of exercise. Column four is the most similar conditions to the experiments in our article. This comparison reveals that a negligible amount of protein is metabolized in KE conditions, and there looks to be a slight decrease in glucose metabolism as well.

The second study compared the differences between what the athletes supplemented prior to exercise, once again observing blood profiles. There was a total of three trials, supplementing either KE, CHO, or a fat drink prior to each trial, and in all trials drank KE 45 minutes into the cycling bout. After 30 and the 45 minute mark, the KE trial yielded a whopping 50% lower blood lactate levels compared to the CHO or fat trials. This means that at the same intensity, the athletes were twice as close to their lactate thresholds when supplementing CHO or fat. In addition, blood glucose levels were significantly higher post exercise in KE trials, and glycolytic intermediates (pyruvate) were lower as well. This eludes to a decreased usage of the glycolytic (CHO burning) cycle in exercise allowing other more efficient metabolic cycles to take over. These findings support the theory that even the presence of KE triggers a suppression of glycolysis in an attempt to preserve CHO.

Study three examined if there was a synergistic relationship between KE and CHO, as there is such an effect from ingesting a combination of protein and CHO to improve protein absorption. Using three separate trials, this study tested KE+CHO, CHO only, and B3 vitamin supplementation prior to a 1 hour cycling bout at 75% Wmax. The B3 vitamin acted as a control in order to keep the subjects from knowing which dosage they received. The results were similar to the previous studies in showing a lower lactate concentration in the blood profiles, but what was novel to this study was the normal spike of insulin after the KE+CHO drink. This demonstrated that the normal insulin release still occurs when KE is present. Raised insulin secretion in the body triggers the body to absorb a greater amount of nutrients in the blood stream, possibly helping the body absorb more KE.

The fourth study examined fat and CHO stores in the muscle after a prolonged (2 hours) cycling trial at 70% Wmax when ingesting KE+CHO. Comparing 2 different trials KE+CHO vs CHO only, the study found a 24% decrease vs 1% decrease in intramuscular fat post-exercise. They also found significantly more intramuscular CHO stores in the KE trials, again affirming the inhibition of glycolysis, and increasing aerobic oxidation (fat burning metabolism).

The fifth study finally addressed performance by prescribing 1 hour ride at 75% Wmax, then performing a 30 minute time trial for max distance. In the time trial, cyclists improved an average of 411 meters further in the KE+CHO trial, which translates to only about a 2% improvement in performance. This is still better than what has been found through starvation ketosis, but does not give a major leg up on performance.  After major findings such as a 50% reduction in lactate during exercise, the 2% improvement in performance is a good lesson that performance is a macro-variable and lactate is just one of the innumerable micro-variables that go into the total equation.

Overall, these studies do a good job of demonstrating that the ideal use for nutritional ketosis would be for long duration or repeated endurance exercise, and how the preservation of CHO stores possibly produces these advantages in performance. In addition to understanding the efficacy of nutritional ketosis study three also reveals the advantages to dosing KE with CHO to induce greater absorption, and maximize the effects of the supplement. Lastly, I do want to point out that as this supplement is promising, more research is needed to understand the implications on novice level athletes, if there are greater advantages in repeated bouts, or if this may even be a useful product to assist in fat loss while maintaining lean body mass.

Jack Rummels

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