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One of the greatest challenges of training is "functional overreaching". Pushing your maximal capacity results in stress that leads to beneficial adaptations...making your body stronger, faster, & better.

What happens when you do it wrong? Aptly named, "non-functional overreaching" occurs.

Nothing will help besides rest and recovery. In the case of "overtraining", the more serious form of overreaching, it might take months for even the most elite athletes to bounce back.

A recent study found promising signs that ketone esters can alleviate overreaching symptoms. The researchers didn’t necessarily look at how ketones acutely influence exercise performance, but rather how consistent supplementation could affect recovery and training capacity.

The lead researcher, Professor Peter Hespel, described the potential effect of ketones in recovery as “unseen” and “many times greater” than what he’s seen with other nutritional supplements.

Geoffrey Woo breaks this study down, analyzes the experiment structure, and digs deep into the findings for every last nugget of applicable information.

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Overview & Context

Today, we’re talking training. More specifically, what happens when you over-load or overtrain, which can happen in sporting and survival situations. A recent study that made headlines looks at a nutritional intervention, the ketone ester, and how it mitigate negative overtraining effects.

Overload training is a strategy used by athletes in virtually all sport. The concept goes like this: in order for a muscle or energy system to improve in size, strength, or endurance, it must be challenged regularly and intensely — you’ve got to overload it on occasion. Pushing the body right up to its maximal capacity results in beneficial stress to strengthen it. It's "what doesn't kill you makes you stronger." With proper recovery and nutrition, overload training leads to adaptations that make the body stronger, faster, and better in the long term — this is what is known as functional overreaching.

But, what happens when we train and don’t allow ourselves enough time to recover and repair? The result is injury. Typically, training drives anabolic signals — anabolic referring to growth. Too much work and not enough recovery, however, leads to a catabolic state — a state of breakdown. This is known as non-functional overreaching. If an athlete is in this state, nothing will help besides rest and recovery. It might take weeks of downtime to bounce back from a bad spell of overreaching. In the case of "overtraining", the more serious form of overreaching, it might take months of hard-core recovery to get an athlete back to baseline. If you’re like me, extended, forced downtime is something I want to avoid.

The goal of every athlete is, basically, balancing training and recovery, to ride the fine line between optimal performance and working just way too hard. You want to be fit on the starting line, but that means getting there in one piece.

But this isn't just for athletes. For people like myself trying to live a long, healthy and active life, we also need to find our own line of training and recovery.

Proper nutrition is one way to promote recovery from workouts, and mitigate overtraining risk. For the most part, athletes are advised to prioritize post-exercise intake of protein and carbohydrates or consider antioxidant supplements for recovery. Some evidence here, but what's the latest physiological understanding ? Research on the application of ketones for the management of performance is being conducted. It’s an exciting area of research, and the paper we'll be diving into today paints a very bright future for this application.

The study is titled “Ketone ester supplementation blunts overreaching symptoms during endurance training overload”, and was recently published in the Journal of Physiology in April 2019. It was led by Professor Peter Hespel at KU Leuven who heads the Belgian research team conducting the study. Hespel also works with the QuickStep pro cycling team and the UPlace-BMC Pro triathlon team — clearly these findings might have direct application to his athletes, making the work all the more interesting. The study was designed to “mimic” what a team of cyclists might experience in something like the Tour de France. Clever stuff.

The group conducting the study set out to answer this question— can ketone ester supplementation during endurance exercise training prevent symptoms of overreaching? Due to what they already know about ketones and the research that’s been done, they hypothesized that the ketone would help lessen the effects of fatiguing endurance training, maybe even enhance endurance performance during and after a hard-core training stint. The study didn’t necessarily look at how ketones acutely influence exercise performance, but rather how consistent supplementation could affect recovery and training capacity. Let’s take a look at how the study was set up.

Experiment Structure

Participants in this study were 18 young healthy males who the authors classified as “physically active.” They weren’t ironmen or Tour de France cyclists...but they weren’t couch potatoes either. Researchers split them into two different groups, and this determined what nutrition intervention they got. However, regardless of the group, everyone was placed on the same training program: a three week endurance training regimen with a total of 28 sessions — often two training sessions per day. That’s about 10-11 workouts each week. A serious exercise load — and that was the goal. Training was specifically designed to be overload training. This is important — the researchers had the explicit goal of bringing each participant to a state of overreaching!

The major difference in the groups was what type of nutrition they received after training. Whenever they finished a workout, each group was given a protein-carbohydrate rich drink to promote recovery. One group (the experimental group) also received 25g of a ketone ester (the one in H.V.M.N. Ketone) with their recovery beverage. The same group also consumed another ketone ester right before every workout, and another prior to going to bed. If you’re wondering, yes, thats three ketone esters consumed per day. The other group (the control group) were given a drink with the same volume and consistency 3 times per day, but instead of ketones, it contained a blend of medium chain triglycerides and flavors to mimic the taste of H.V.M.N. ketone. This is what’s known as a “blinded” study — the participants had no idea if they were getting the ketone or the imposter. Studies do this in order to make sure any effects seen are due to the treatment being given, and not the “placebo effect.”

What did they measure?

One of the primary outcomes was performance. At the beginning, middle, and end of training, each participant completed a 30 minute cycling time trial and a 90 second sprint. They also performed a 120 minute endurance test on day 18 — about halfway through the study. Why all of these tests? These would allow researchers to see two things. 1. Are the participants improving with training and 2. Is the training leading to overreaching? If the training was too harsh, performance might start to decline. In the case of this study, that would mean the protocol was doing its job.

In addition to performance, they also assessed body composition, bone mineral content, and several indicators mental health, recovery and stress. They wanted to know how the subjects bodies were responding, but also how their minds were handling the training. A slew of blood biomarkers were also analyzed that might just be related to overtraining. Blood samples were taken at various study time points and analyzed for BHB (to validate that subjects were actually in ketosis) and blood markers related to overreaching: things like the hunger hormones leptin, ghrelin, and GDF15, osteocalcin, the inflammatory markers IL-6, stress hormones like cortisol and ACTH, plus immune-related T-cells, and blood glucose. This study was many things, and comprehensive was one of them.

Experiment Results

So, what happened?

In the ketone ester supplemented training group, time trial performance improved 4.9% in the post-test, but interestingly also after 3 and 7 days of recovery. In fact, their performance was actually BETTER during the recovery period than right after training. What about the group not given the ketone? Time trial performance only improved after day 7 of recovery — this is classic overreaching.

The ketone ester group also had a 15% higher power output during the ultra-long 2 hour endurance test than the control group. For both groups, power output declined during the 90 second sprint in the post-test period, and this only returned to normal after 3 days of recovery.

Let’s go over some other key results briefly — many hormonal biomarkers indicated more stress in the control group vs. the ketone ester group. Nighttime release of adrenaline and noradrenaline increased as a result of training. In addition, both groups indicated that they might have been approaching overreaching based on self-reported questionnaires. Total stress scores went up, while recovery scores went down. After training and during the recovery period, these scores returned to normal.

Another interesting finding related to the participants’ heart rate. During overreaching, an imbalance of sympathetic (“the fight or flight”) and parasympathetic (“rest and digest”) activity leads to a lower heart rate — a classic sign of overtraining. Ketone ester intake, while not totally preventing this, led to less of a decline in heart rate — this likely allowed the group to exercise harder and prevent some of the autonomic system imbalance. In terms of working harder, this was actually confirmed by the study, since by week 3, the ketone ester group had a 15% higher training load output than the control group.


One strength of this experiment was the training program — which definitely led to a state of physiological overreaching confirmed by multiple different measures — including appetite suppression, hormone dysregulation, performance impairments, and lower mental well being. Importantly, the ketone ester group who were consuming a KE three times per day, experienced significantly less impairment in many of these outcomes— basically showing a lot fewer signs of overreaching no matter what was measured.

A few nuanced results are also pretty important. First of all was what happened to food intake and appetite in the ketone group. While the control group kept their calorie intake constant throughout the training period and ended up in a caloric deficit, the ketone ester group actually increased intake to match their increased energy expenditure — they were able to balance their energy needs perhaps because they maintained appetite. This might be a crucial reason why they were able to stave off overtraining and improve performance. They were simply better fueled throughout the study. This might possibly confound the results, but it also suggests that exogenous ketones might be having some effect on appetite regulation for athletes in training that hasn’t been studied yet.

Back to appetite for a second. This study uncovered a novel appetite regulating hormone that might have played a role in how much food the athletes consumed. This hormone is called growth differentiation factor-15, or GDF 15. The authors also propose that this might be a novel, undiscovered biomarker for overtraining. This would be super valuable, since no true markers exist right now. Throughout the study, GDF-15 levels rose in the control group, suppressing appetite. In the ketone group, GDF-15 levels were lower, perhaps making them hungrier.

Being in ketosis might not have been responsible for the beneficial effects, per se. Interestingly, blood levels of D-BHB were not different during the training between groups — they were actually both in ketosis at the post-test time point at rest throughout training, confirmed through blood measures. The only difference was right after exercise, when intake of the KE increased blood BHB to about 2.6mmol. While speculative, maybe this difference alone was enough to promote recovery and negate some of the catabolic effects of training. It’s been shown that consuming a ketone ester along with a protein-carbohydrate drink post-exercise can enhance muscle glycogen replenishment and protein synthesis.

These results shed a more positive light on ketone ingestion for endurance athletes. Past studies using ketone salts have that they might lead to GI distress and impaired performance. In this study, GI complaints were low, and no different for the groups consuming 3 KE’s per day compared to the control.

Key Takeaway

The big takeaway here is that a different nutritional strategy — that is, exogenous ketone supplementation, can be used as a training aid to improve performance and perhaps guard against wear and tear from intense training that might eventually lead to overreaching or burnout. Ketone ester supplements might just be the next big thing in sports nutrition for athletes. In an interview with a European sports website, Hespel described the potential effect of ketones in recovery as “unseen”, but also said that the ketone boost was “many times greater” than what he’s seen with other nutritional supplements.

Obviously, more work needs to be done, and overreaching is a complex phenomenon. Nevertheless, future studies using H.V.M.N. Ketone will hopefully build on the knowledge gleaned here.

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