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There is a growing market in sports nutrition for supplementation with ketone bodies. They come in the form of salts, MCT Oil – a precursor to ketones – and off-the-shelf ketone esters.

In 2017, according to the study, “Ketone Bodies and Exercise Performance: The Next Magic Bullet or Merely Hype?” indicated that for now, it’s all hype:

“At present, there are no data available to suggest that ingestion of ketone bodies during exercise improves athletes’ performance under conditions where evidence-based nutritional strategies are applied appropriately.”

However, all is not lost – in case you just invested in a cupboard full.

Peter Hespel, Professor of Exercise Physiology at KU Leuven in Leuven Belgium at the Department of Movement Sciences and his research team, which includes Chiel Poffé, Monique Ramaekers, and Ruud Van Thienen led an interesting study with cyclists who supplemented their diet with a ketone ester (KE). Results indicate that ingesting ketones with little to no other dietary changes may attenuate some negative training effects from periods of intense volume and effort.

In the study, that has been peer-reviewed and accepted for publication as of April 30th, Hespel referred to the heavy training as “overreaching”.

Apparently, there is no support at this time that a ketogenic diet is more beneficial with the supplementation protocol of the ketone ester, in fact, the opposite may be true.

The study is titled: “Ketone ester supplementation blunts overreaching symptoms during endurance training overload”, in the Key Points section he wrote about athletes overreaching and being in a catabolic state.

Asked to define what physiological changes typically make up a so-called catabolic state in endurance training, he told Athletics Illustrated, “The catabolic state developed during overreaching or overtraining, is multifactorial, of course, but the catabolic events happening often do not only result from the strenuous exercise per se, but also from the energy deficit caused by the imbalance between exercise energy expenditure, and nutritional energy intake, which leaves insufficient energy for optimal function of basal physiological functions.”

In other words – as commonly practiced – supplementation may be required depending on how much volume and how intense one trains.

Supplementing specifically with ketones, (but not when keto-adapted through diet restriction of carbohydrates – a very popular weight loss diet or lifestyle – program) may be the latest buzz in training nutrition.

Hespel says that for over-trained endurance athletes this typically results in a drop of the hormone testosterone as well as bone resorption, drop of red blood cell mass, and muscle mass desecration.

“In female athletes, menstrual dysfunction is an additional problem. At the neural side, it is clear that the autonomic nervous system seems to ‘protect’ the body from additional physiological overuse. The output of the sympathetic nervous system (the ‘activator’ system), relative to the parasympathetic system (the ‘inhibitor’ system), is decreased, and this results in lower heart rates for a given submaximal workload, and an inability to elicit maximal heart rate during maximal exercise.”

For athletes to improve there is a fine line between pushing too far, causing this catabolic state and the stimulus-adaptation-improvement paradigm that athletes tight-rope-walk.

Hespel tells us that ketone supplementation attenuates by stimulating signalling in muscle cells – a pivotal signalling molecule which is responsible for the regulation of muscle protein synthesis. The pivotal signalling molecule is named mTOR (https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5440563/).

Although on the surface, one may take the leap and guess that the KE supplementation helps prevent injuries and delayed onset muscle soreness (DOMS), no such claim is being made, however, there is some evidence that it exerts anti-inflammatory effects – more to come on this.

For runners, it is important to know that the study was done with cyclists who do not induce the same rate of muscle damage because of the absence of eccentric contractions. Whereas with running, foot strike force between impact and active peak loads can be two to four times one’s body weight – it is a different form of exercise, muscularly-speaking.

Interestingly, Hespel and his team found that the athletes spontaneously ingested more carbohydrate during week three of the study. The only food intake that was controlled during the study was the intake of KE or the intake of a protein-carbohydrate mixture (‘recovery shakes’) immediately after training.

“Nonetheless it did not result in different muscle glycogen concentrations between the groups, either before or after exercise.”

Hespel was clear that being on a ketogenic (very low carb/high fat/moderate protein) diet did not provide any training benefits.

“No, certainly not. If one combines such an intensive training program with a so-called ‘ketogenic diet’ recovery will be markedly impaired, and I doubt that KE intake might still be useful to stimulate recovery in such inappropriate dietary choice. A low carb diet in conjunction with such intensive training program will for sure result in a gradual decline in muscle glycogen content and will result in markedly impaired endurance exercise performance. Similarly, if you would combine a Tour de France ride with a low-carb diet, you are ‘out’ after just a couple of stages.”

We surmise, even earlier – you wouldn’t even qualify.

According to Canadian Exercise Physiologist Trent Stellingwerff, an athlete’s V02max can be hampered by up to 5% on a ketogenic diet. This is massive for an elite athlete and noticeable for any distance runner in any event up to the half-marathon and potentially up to the marathon for sub-elite and elite runners.

“KE intake during the most ‘killing’ training periods will stimulate recovery and help to improve training quality, i.e. maintain higher training intensity and volume. Logically this should result in improved functional overreaching (he actually wrote functional in all caps) and better super-compensation. But more studies need to be done to confirm such effects in different training modes (endurance training, resistance training, anaerobic capacity training, etc).”

Careful, if you plan to purchase a ketone supplement to take advantage of the apparent benefits cited by Hespel. Some products do not contain the amount of ketones that they claim, hence a recent tweet by the physiologist himself,

And if you plan to supplement your diet with whole foods to take in the volume of ketones required to attenuate a catabolic state from overtraining or intense training, forget it.

“No, that is not possible. The only strategy would be complete fasting for about a week, which would prevent you from doing any serious training. And with a low carb – high-fat diet, blood ketone levels are lower than with oral ketone ester intake, and the lack of carbohydrate intake in recovery would definitely impair training quality during such dietary approach.”

Read the abstract here: https://physoc.onlinelibrary.wiley.com/doi/10.1113/JP277831