Ketones: Fuel or Flaw?

by | May 1, 2026 | Supplements

Ketone supplements are enjoying a moment. Marketed heavily to endurance athletes, they promise a compelling array of benefits, including a “one-of-a-kind” boost in “clean energy”, maximum endurance, better recovery, and improved brain clarity and focus. One brand, Ketone-IQTM, makes all of these claims at a cost of roughly $45 per 10 servings. With suggested intakes of 1-3 servings per day, this is not a trivial investment.

This raises the question: are we buying performance or just the promise of it?

Interest in exogenous ketone supplementation (EKS) has been driven largely by endurance athletes, with visibility rising sharply between 2017 and 2019 through professional cycling sponsorships and endurance sport media. [1] Today, the global EKS market is projected to exceed $650 million by 2027.

At their core, ketone supplements provide an alternative fuel source. Typically delivered as ketone esters or ketone salts (see Note below), they elevate circulating levels of beta-hydroxybutyrate (BHB), a molecule the body naturally produces and metabolizes during fasting or carbohydrate restriction. The appeal is intuitive. If ketones can serve as a fuel source, perhaps they can spare glycogen and enhance performance.

But as is often the case in nutrition science, plausibility is not proof.

Part 1. Performance: A Theory in Search of Confirmation

Research on the effects of ketones on sports performance is mixed, with significant knowledge gaps. There are theoretical ergogenic benefits, such as serving as an alternative substrate for energy production, improving economy, and reducing reliance on carbohydrates (CHOs). But when tested on athletes, results are inconsistent and underwhelming. [2,3]

One study on well-trained runners compared CHO intake alone, CHO plus ketones, and ketones alone, and the impact on running economy. [4] The ketones were taken before and during the exercise test. Running economy improved in the ketone-only condition compared with carbohydrate alone. However, this advantage vanished when ketones were co-ingested with carbohydrate, which is how most athletes would realistically use them. Notably, time to exhaustion did not differ between conditions.

Other research suggests that when carbohydrates are readily available, ketones contribute only minimally to energy production in the mitochondria. [5]

More concerning, there is a consistent signal that ketones may impair performance during high-intensity, glycolytic efforts. Proposed mechanisms include:

  • Lowered blood pH
  • Inhibition of key glycolytic enzymes
  • Increased gastrointestinal distress

In other words, the very conditions where performance margins matter most may be where ketones are least helpful — or even counterproductive. [6]

Ultimately, ketone research is quite diverse in its design, dosing strategies, and exercise modalities, and athlete types (such as elite versus amateur), making it difficult to obtain a clear picture.

A 2022 review succinctly captured the current state of the science:

     Despite extensive research, there is remarkably little consistent evidence that ketone supplementation improves athletic performance. [2]

Part 2. Recovery and Adaptation: A More Intriguing Story

Emerging research suggests that ketones may influence recovery and exercise adaptations. Here, the evidence is more interesting, but still preliminary.

Sleep

Heavy training blocks and multiday events can disrupt sleep. Some studies show post-exercise and pre-sleep ketone ingestion may mitigate this disruption. However, it is unclear whether athletes with already good sleep quality would benefit from ketones. [7]

Blood and Capillary Adaptations

A 2023 study reported increased erythropoietin (EPO) and muscle capillarization following ketone supplementation during a short period of training overload. [8] Another study showed post-exercise increases in EPO concentrations in healthy, active men when ketones were ingested immediately after exercise. [9] However, two other studies did not observe this effect (although there were important differences between the study designs). [10] Should ketones raise EPO, the question remains whether this is sufficient to translate into increased hemoglobin mass and subsequent performance improvements.

A 2023 study reported greater angiogenesis (i.e., increased capillary density) following a 3-week endurance training overload period with repeated post-exercise ketone ingestion. [11] Increased capillarization is a primary muscular adaptation to endurance training; however, excessive training can blunt this response. This work was conducted in young healthy males, so an important next step is to determine whether similar effects are observed in well-trained athletes, masters, and female athletes.

Mitochondrial Function

Animal studies suggest ketones may induce favorable mitochondrial changes, particularly in metabolically compromised muscle. It remains unclear whether well-trained endurance athletes — who already possess high mitochondrial density and function — would see meaningful benefit. [5]

Inflammation and Oxidative Stress

While excessive and chronic inflammation can impair recovery, some degree is necessary for adaptation (a topic we explore in Staying in the Game). Current evidence does not clearly show that ketones improve this balance in athletes. [7]

Glycogen Resynthesis and Protein Metabolism

Ketones may enhance glycogen resynthesis and reduce protein oxidation under certain conditions (such as when carbohydrate availability is low). [7] However, the critical question remains: Do ketones provide additional benefit beyond adequate carbohydrate and protein intake? So far, the answer appears to be: not much.

The Bottom Line

Ketone supplements occupy an interesting space, scientifically intriguing and commercially successful, but not yet convincingly effective.

  • Performance benefits: largely unsupported
  • High-intensity exercise: potential downside
  • Sleep: maybe during periods of disrupted sleep during multi-day events
  • Recovery and adaptation effects: promising but preliminary
  • Cost: substantial

Ketones may yet find their niche, but for now, they are best viewed not as a breakthrough but as a promising hypothesis awaiting confirmation.

 

Note: Ketone esters are ketone bodies, such as BHB, bound to molecules like 1,3-butanediol (the primary ingredient in Ketone-IQ is R-1,3-butanediol). Ketone salts are ketone bodies (BHB) combined with calcium, magnesium, or potassium salts. While ketone salts are generally less expensive, the gastrointestinal (GI) tract often struggles to handle the high salt-ion load. [12]

References

  1. Evans M, Cogan KE, Egan B. Metabolism of ketone bodies during exercise and training: physiological basis for exogenous supplementation. J Physiol. May 1 2017;595(9):2857-2871.
  2. Margolis LM, O’Fallon KS. Utility of ketone supplementation to enhance physical performance: A systematic review. Adv Nutr. Mar 1 2020;11(2):412-419.
  3. Valenzuela PL, Castillo-García A, Morales JS, Lucia A. Perspective: Ketone Supplementation in Sports-Does It Work? Adv Nutr. Mar 31 2021;12(2):305-315.
  4. Brady AJ, Egan B. Acute ingestion of a ketone monoester without co-ingestion of carbohydrate improves running economy in male endurance runners. Med Sci Sports Exerc. Jan 1 2024;56(1):134-142.
  5. Evans M, McClure TS, Koutnik AP, Egan B. Exogenous ketone supplements in athletic contexts: Past, present, and future. Sports Med. Dec 2022;52(Suppl 1):25-67.
  6. Leckey JJ, Ross ML, Quod M, Hawley JA, Burke LM. Ketone diester ingestion impairs time-trial performance in professional cyclists. Front Physiol. 2017;8:806.
  7. Robberechts R, Poffé C. Defining ketone supplementation: the evolving evidence for postexercise ketone supplementation to improve recovery and adaptation to exercise. Am J Physiol Cell Physiol. Jan 1 2024;326(1):C143-c160.
  8. Poffé C, Robberechts R, Van Thienen R, Hespel P. Exogenous ketosis elevates circulating erythropoietin and stimulates muscular angiogenesis during endurance training overload. The Journal of Physiology. 2023;601(12):2345-2358.
  9. Evans E, Walhin J-P, Hengist A, Betts JA, Dearlove DJ, Gonzalez JT. Ketone monoester ingestion increases postexercise serum erythropoietin concentrations in healthy men. American Journal of Physiology-Endocrinology and Metabolism. 2023;324(1):E56-E61.
  10. Egan B. Acute and intermittent exogenous ketosis to support recovery from exercise and adaptations to exercise training: A narrative review. Scand J Med Sci Sports. Nov 2025;35(11):e70158.
  11. Poffé C, Robberechts R, Van Thienen R, Hespel P. Exogenous ketosis elevates circulating erythropoietin and stimulates muscular angiogenesis during endurance training overload. J Physiol. Jun 2023;601(12):2345-2358.
  12. Goncalves B. Brendan Egan, PhD: Scientfic Triathlon Podcast; September 11, 2023.