Are Ketones the Missing Piece in Your Recovery Plan?
We get better during recovery, not when we train.
It’s a cliche, but it’s true.
Recovery is a critical period during which the body works to replenish its energy stores and repair damaged muscle tissue. Carbohydrates (stored as glycogen in muscles and the liver) play a pivotal role in this process. The faster and more effectively these glycogen stores are replenished, the better the body can recover and prepare for the next bout of exercise, whether that’s in a few hours or the next day. Delaying carb intake for just 3 hours after exercise (as opposed to consuming them right after) impairs next-day performance, even when sufficient calories and carbs are consumed throughout the rest of the day.
Traditional strategies to enhance glycogen resynthesis post-exercise include consuming carbohydrates at a rate of 1–1.2 grams per kilogram of body weight per hour, often combined with protein to maximize muscle glycogen synthesis. Glucose-fructose mixtures can further enhance liver glycogen replenishment. However, with the demand for rapid recovery in athletes who train multiple times a day, additional strategies to accelerate glycogen resynthesis are always being explored, and ketone esters have emerged as a promising nutritional intervention.
Ketones are molecules produced by the liver during periods of low carbohydrate availability, such as fasting or ketogenic diets, and can serve as an alternative energy source for the brain and muscles. Ketone esters—a supplement form of ketones—have been shown to influence metabolism by suppressing glucose production and potentially enhancing glycogen storage.
By modulating how the body uses and stores energy, they could offer a way to optimize recovery and prepare athletes for their next performance. There are also several other compelling mechanisms, although admittedly understudied at present, that position exogenous ketones as a worthwhile supplement to enhance recovery and even attenuate the symptoms of overtraining.
The metabolic effects of ketones suggest that—when combined with adequate post-exercise nutrition—they might be able to enhance our body’s ability to store and replenish carb stores, accelerating the recovery process. Does this happen? And if so, would it have any impact on subsequent exercise performance? That’s what a new study investigated.
Published as a pre-print (i.e., it hasn’t yet been peer-reviewed), the study employed a randomized crossover design with thirteen endurance-trained male participants (peak oxygen uptake of at least 45 ml/kg/min and at least two years of running experience/three hours of endurance training per week).
Each participant completed two conditions, both of which included two exhaustive running bouts performed four hours apart. The first bout began with a five-minute warm-up at 50% VO2 max, followed by alternating one-minute intervals at 90% and 50% VO2 max. As participants fatigued, the higher intensity was gradually reduced to 80% and then 70% VO2 max until they could no longer sustain the effort. This approach ensured that participants reached a high level of fatigue and depleted their glycogen stores.
After the first running bout, participants entered a four-hour recovery period. During this time, they consumed beverages every 30 minutes containing sucrose (1 g/kg/hour) and whey protein (0.4 g/kg/hour). In one condition, the beverage was supplemented with 0.29 g/kg/hour of ketone monoester, while the other condition used a taste-matched, isoenergetic placebo made from fat. The ketone used in this study was Delta G ketone ester, and the participants (based on average body weight) consumed ~20 grams per hour—that’s about one serving every hour for four hours.
After the recovery period, participants performed a second run to exhaustion at a steady 70% VO2max. This test was designed to measure their endurance capacity following the different recovery interventions.
There were two main outcomes we’re interested in: carbohydrate (glycogen) storage and performance during the second time-to-exhaustion test. In this study, the researchers gave the participants a special type of carbohydrate labeled with a tiny “tag” (a different form of carbon called 13C). This is similar to adding a tracer to the fuel in a car to determine exactly how much of that specific fuel is used up (in this case, how much was present in the participants’ breath). The more tagged carbon they found in the breath, the more of the ingested carbohydrate had been burned by the body. This method enabled the researchers to track how effectively the body utilized the ingested carbohydrates for energy and how much was being stored.
Results
One of the standout findings was that ketone ester ingestion led to greater retention of ingested carbohydrates compared to the placebo condition. Participants who consumed ketone esters retained about 220 grams of ingested sucrose versus 206 grams in the placebo condition—the ketone esters helped the body store more of the ingested carbohydrates rather than immediately burning them for energy.
Additionally, blood glucose levels were significantly lower in the ketone ester condition compared to the placebo. By the end of the recovery period, blood glucose was more than 1.2 mmol/L lower (~20 mg/dL) in the ketone ester group. Ketone esters influenced glucose metabolism by reducing circulating glucose levels.
As expected, blood β-hydroxybutyrate (a type of ketone body) levels were significantly elevated in the ketone ester condition, reaching around 4 mmol/L, compared to negligible levels in the placebo condition, confirming that the ketone ester supplementation effectively raised circulating ketone levels which even persisted into the second exercise test at levels around 1–2 mmol/L (still ketosis levels).
Blood lactate concentrations fell during the recovery period in both conditions, with no significant difference between the ketone and placebo groups.
Lactate levels were also no different during the second exercise test when comparing the two conditions. So, while ketone esters influenced carbohydrate metabolism and glycemia, they did not significantly impact lactate levels during recovery or exercise.
Despite the metabolic changes observed, there was no significant difference in the time-to-exhaustion during the second running bout. Participants ran an average of 52 minutes with ketone esters and 54 minutes with the placebo. The enhanced carbohydrate storage during the recovery period didn’t translate into enhanced performance. While there was a slight increase in lower gastrointestinal symptoms in the ketone ester group during the second exercise trial, these were still rated as mild.
My Takeaway
The findings from this study offer valuable insights for endurance athletes and those looking to optimize their recovery strategies. While ketone esters did not enhance subsequent exercise performance in this specific study, they did show potential in improving carbohydrate retention and stabilizing blood glucose levels.
For athletes who engage in multiple training sessions per day or need to maximize glycogen storage between workouts, incorporating ketone esters could be a useful tool to enhance recovery. I think it’s worth noting that while we didn’t observe a performance benefit in this single-day study, enhanced glycogen replenishment, when extrapolated over days and weeks of training, could lead to notable performance improvements if it allows for a higher sustainable training intensity.
On a personal note, I’ve been using post-exercise ketones during my training (I use ketone-IQ, a different ketone than that used in this particular study), especially after hard interval workouts or long runs of around two hours or more. I typically take these ketones along with my post-exercise meal, and it’s encouraging to see evidence that supports how this might expedite my recovery by increasing muscle glycogen storage. It’s another tool in the toolbox for athletes aiming to fine-tune their recovery and get the most out of their training sessions (but of course, it’s not a miracle performance enhancer).
While the metabolic benefits of ketones are clear, the impact on performance might vary depending on the type and timing of exercise—the data on direct measures of exercise performance aren’t that convincing. Combining ketone esters with established recovery practices, such as proper carbohydrate and protein intake, is the most effective approach to optimizing recovery.
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