In endurance sport, few supplements have generated as much buzz – or confusion – as exogenous ketones. Hailed by some as the new frontier in performance and recovery, and dismissed by others as overhyped and over-marketed, ketones have carved out a controversial place in sports nutrition. So what’s the truth?
To better understand the emerging science, we partnered with one of the most trusted minds in the field: Dr. Dan Plews, a renowned exercise physiologist, researcher, and elite endurance coach. Not only has Dan tested exogenous ketones personally, but he’s also conducted research in the area, reviewed the literature extensively, and worked directly with top-level athletes curious to explore whether ketones can offer a competitive edge.
His verdict? Ketones aren’t magic. But in the right context, and with the right strategy, they can offer benefits worth considering.
Not All Ketones Are Created Equal
Before diving into the potential benefits of ketones, it’s key to understand the different types available, because not all ketones are created equal.
There are three main forms on the market today:
- Ketone Salts (e.g., KetoSports): These combine the molecule of interest, beta-hydroxybutyrate (BHB), with minerals like sodium, magnesium, or calcium. While they’re more affordable and widely available, they’re also less effective at raising blood ketone levels, and you have to take quite a lot to see any effect. This means you’re also ingesting a large dose of salts, which can lead to GI discomfort and, as Dan puts it, “make you very salty.”
- Ketone Esters (e.g., deltaG, Ketone-Aid): These are the most potent and best studied form of exogenous ketones. They raise blood BHB levels quickly and reliably. However, they also taste notoriously bad and are by far the most expensive.
- Ketone Precursors (e.g., Ketone-IQ, Kinetik): These are molecules like 1,3-betanediol that the body converts into ketones. While less potent per dose than esters (you need to consume more to reach the same blood concentration), they may be easier to tolerate and more accessible. However, because of their alcohol backbone, they come with a caution: some people may experience mild intoxication, dizziness, nausea, and/or GI distress.
For Dan, ketone esters stand out as the most research-backed and performance-relevant, and they’re what he consistently uses across racing, training, and recovery.
Ketones for Race-Day Performance: Any Real Benefit?
The performance-enhancing potential of ketones is where some of the hype lives, but it’s also where the science is most mixed.
“I had them in my bottle back in 2018,” Dan says, referring to his age-group world record performance in Kona that year. “So I guess you could call me an early adopter,” he adds with a smile.
In Kona, Dan’s nutrition strategy included 60 grams of carbohydrates per hour, along with 0.29 grams per kilogram of bodyweight of ketone precursors, sipped continuously throughout the bike leg. At the time, he was using precursors rather than ketone esters, as the latter were not yet publicly available. Importantly, he mixed the ketones into his nutrition bottles to distribute the intake evenly, helping maintain his blood BHB levels within the target range of 1-2mmol/L.
By the time he raced Ironman California in 2022, where he became the first-ever age-group athlete to break the eight-hour barrier, Dan had refined his approach. He had switched to 32 grams of ketone esters over the course of the bike ride, and his bottles now also included medium-chain triglycerides (MCTs) to help further stabilize blood ketone levels, plus electrolytes to buffer the mild acidosis that ketones can produce.
If you’re considering mirroring Dan’s strategy in your next race (after testing it in training, of course!), he recommends the protocol he used at Ironman California: combining carbs and ketones with a tablespoon of MCTs and electrolytes. A starting dose of 0.25 to 0.29 grams of ketones per kilogram of body weight works well for most athletes.
To fine-tune your intake, Dan suggests experimenting with different amounts during training while tracking your blood BHB levels. Individual responses to ketones vary, so this is the most accurate and personalized way to ensure you stay in the 1-2mmol/L sweet spot. However, if you prefer not to test blood levels, the 0.25 to 0.29 range is a solid place to start.
But let’s get back to the question: do ketones actually improve performance?
Current evidence suggests that ketones are unlikely to help (and may even impair!) high-intensity efforts (e.g., 60 minutes or less at or above threshold). However, some studies have suggested a potential marginal benefit in longer, steady-state efforts lasting three to four hours or more – the kind of intensity typical in Ironman racing, where athletes sit just above their aerobic threshold (LT1). And that’s exactly the context in which Dan used them.
Beyond pure physical performance, Dan consistently highlights a mental edge: improved focus, cognitive clarity, and reduced perceived effort in the final hours of racing – an effect supported by research. For long-course athletes, even those mid-pack, the mental sharpness in itself could make ketones worth exploring.
Key Takeaway: Based on current research, ketones are unlikely to deliver noticeable physical performance gains on race day. But for long-course athletes, they may offer mental benefits worth considering (if you have the budget and are able to test them in training first).
The Stronger Case: Ketones for Recovery and Adaptation
“I used ketones in my Ironman racing, and I still use them now ,” Dan shares, “but now it’s for the adaptation and recovery benefits.” Having achieved every age-group milestone he set out to accomplish in triathlon, Dan no longer races long-course and has shifted his competitive focus to HYROX (Stay tuned – we’ve got a HYROX piece coming soon for those interested in trying it!)
“In Brisbane, I competed in two HYROX competitions back-to-back,” Dan continues. “One was in the evening, and the other was the next morning. I took ketones in between, and it felt genuinely game-changing. It’s almost weirdly instant.”
This highlights what Dan sees as the second and stronger case for ketones: supporting recovery and adaptation between hard sessions or events.
Evidence suggests that ketones taken between hard sessions can meaningfully enhance training sustainability and help maintain power output – or more broadly, performance – during intense training blocks. Research also points to their role in stimulating angiogenesis (the formation of new blood vessels) and naturally boosting erythropoietin (EPO), a hormone that promotes red blood cell production and enhances the body’s ability to deliver oxygen to working muscles.
Ketones may also support better sleep, a critical yet often underestimated driver of recovery. This indirect effect could further enhance the body’s capacity to adapt and perform under heavy training stress.
Beyond these more well-established benefits, early research suggests additional mechanisms that may contribute to recovery and adaptation. While beyond the scope of this article (findings are still developing), they highlight the broad physiological interest in ketones beyond performance alone.
So, practically speaking, how and when should you take them? One limiting factor for many athletes is cost – high-quality ketone esters aren’t cheap. As a result, Dan recommends using them strategically:
- Prioritize peak training weeks, or big “overload” training blocks, when stress is highest and recovery becomes a key performance driver.
- Use them between back-to-back hard sessions or races, as Dan did during his HYROX double – a context where faster recovery can directly impact next-day performance.
- Time them wisely: If you’re taking them once a day, Dan recommends using ketones before bed. With that said, during his own peak blocks, he typically takes them both post-session and before sleep.
Key Takeaway: For competitive athletes looking to get the most out of themselves, ketones post-training and/or before bed are worth considering. Use them strategically, when recovery matters most, to make the most of your budget.
The Final Word
Ketones won’t turn a mid-packer into a podium finisher, and they’re definitely not magic. But used wisely, in the right context, they can help you train harder, recover better, and stay sharper late in a race. And for some athletes, that edge can be worth it.
For a deeper dive, check out Dan’s YouTube video titled “Exogenous Ketones: When they work, and when they don’t. The Science and Practical Application.” In it, he breaks down the key studies that have shaped his perspective.
Disclaimer: Dan is a DeltaG ambassador, but he emphasizes that the partnership reflects his confidence in the product and the science behind it.
FOOTNOTES
Distributing Ketone Intake For Stable Blood Concentrations: Dan distributed his ketone intake throughout his races by mixing them into his carbohydrate bottles. Rapid ingestion of ketones has been shown to transiently elevate insulin, which can lead to a temporary drop in blood glucose – a potential risk during endurance events where stable glucose availability is key. By spreading the dose out over time, Dan aimed to maintain more stable BHB concentrations in the target range of 1-2mmol/L.
Timing Ketones – Post-Training Versus Before Bed: Some emerging research raises the theoretical concern that taking exogenous ketones immediately post-exercise could interfere with cellular signaling pathways involved in adaptation – specifically AMPK, a key regulator of mitochondrial biogenesis and endurance improvements. While this potential blunting effect hasn’t been conclusively proven in real-world training, it has led experts, including Dan, to be strategic with timing. If you’re taking ketones once daily, Dan recommends doing so before bed, when post-exercise signaling is less relevant, and benefits for recovery and sleep quality may be maximized. With that said, during peak training blocks, he still takes them both post-training and before bed, balancing proven recovery benefits against theoretical (but unconfirmed) adaptation trade-offs.
Key Supporting Research
- Mental Benefits: Exogenous ketosis increases circulating dopamine concentration and maintains mental alertness in ultra-endurance exercise (Poffé et al., 2023).
- Improved Training Sustainability: Ketone ester supplementation blunts overreaching symptoms during endurance training overload (Poffé et al., 2019).
- Angiogenesis and EPO: Exogenous ketosis elevates circulating erythropoietin and stimulates muscular angiogenesis during endurance training overload (Poffé et al., 2023).
- Improved Sleep: Exogenous Ketosis Improves Sleep Efficiency and Counteracts the Decline in REM Sleep after Strenuous Exercise (Robberechts et al., 2023).
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