John Davis

Written by John Davis


Ketones for Runners: Can they boost performance and enhance recovery?

If you took a class on nutrition, the very first thing you would learn is that there are three sources of calories: carbohydrates, fat, and protein.

As all runners know, carbohydrates are the primary fuel if you want to run fast. But there’s a problem with carbohydrates—your body just can’t store that many.

That’s why hitting the wall, or “bonking,” is such an issue in the marathon.

Once you run out of carbohydrates, your ability to produce energy drops dramatically and you have to slow down.

But, there’s a fourth source of energy that might offer a way out of this conundrum, and that is ketones.

You’ve probably heard of the ketogenic diet, which claim to leverage the benefits of ketones, in exchange for a diet that’s almost entirely fat.

In this article, we’re not going to look at whether the ketogenic diet has any fat loss or diet evidence, but rather explore whether ketones can help you run faster?

Ketosis, ketones, and running performance

Ketones are molecules produced when your body metabolizes fat, but they don’t come up much in traditional nutrition because when you are well-fed on a balanced diet, your body does not rely heavily on ketones for energy.

However, ketones play a big role in two situations: fasting and carbohydrate-restricted diets.

If you are fasting, or if you adopt a diet that’s extremely low in carbohydrates, something interesting happens in your blood after about four days: the concentration of ketones increases markedly, which is a sign your body has transitioned to ketosis.

In this state, your body is more readily able to burn ketones for energy during exercise. Burning ketones means your body uses less carbohydrates and produces less lactate, which could theoretically lead to better performance.

Some ultramarathoners have adopted ketogenic diets to shift their body’s fuel sources to rely more heavily on ketones, with the hopes of being able to run further and faster by relying on fat and ketones as a primary energy source.

However, sticking to a ketogenic diet is extremely difficult, and research has found that the lack of carbohydrates can be a real impediment to performance.

According to a 2015 scientific article by Louise Burke at the Australian Institute for Sport, low-carbohydrate diets have repeatedly been shown to impair high-intensity endurance performance because your body down-regulates its use of carbohydrates during exercise [1].

But what if there was a way to leverage the benefits of ketones without actually being on a ketogenic diet?

Could an exogenous ketone supplement help you run faster?

Cutting-edge exercise physiology research has suggested that taking “exogenous ketones” as a supplement might allow your body to lean more heavily on ketones during exercise, without having to restrict your carbohydrate intake.

An influential study published in 2016 in the journal Cell Metabolism made this claim, bolstered by both cellular metabolism data and real time trial performance from elite cyclists [2].

The paper, published by a team of researchers at Oxford, showed that a ketone supplement boosted levels of ketones in the blood, just like going on a ketogenic diet.

Moreover, taking a ketone supplement decreased blood lactate levels and increased performance on a cycling time trial, even when consumed alongside a traditional, sugar-rich sports drink.

These results created quite a stir: a Silicon Valley startup (HVMN) was quickly founded to commercialize ketone ester supplements, and a flurry of research papers followed.

The results since the initial 2016 paper have been mixed: One more study found that ketone supplementation was beneficial for performance, five studies found no effect, and two studies found that ketones actually impaired performance [3].

Part of the trouble with interpreting the wide range of findings is the variability in the types of exercise performed in these studies: one used an 800m running time trial, while another used a 31 km cycling time trial, for example.

Not all studies used exactly the same type of exogenous ketones, either—some used ketone salts, while others used ketone esters.

Exercise biochemists still disagree over whether the ester form is superior to the salt form. And at least one of the studies which reported impaired performance attributed at least part of the problem to “gastrointestinal discomfort”[4]—ketone ester drinks are notoriously foul-tasting (the flavor has been variously compared to rubbing alcohol or nail polish remover [5]).

Exogenous ketones and post-run recovery

Some of the more interesting research since 2016 has been on the recovery aspects of ketone supplementation.

A paper published in Frontiers in Physiology demonstrated that supplementing with ketone esters during recovery increases the activity of mTORC1, a cellular signalling pathway that’s intimately involved with muscular growth and recovery [6].

These findings suggest that ketone supplementation could be a useful recovery strategy, particularly after long, tough training sessions that damage your muscle fibers, like a hill workout.

The bottom line: are ketones worth it for runners?

Since ketone supplementation is so new, there’s a limited pool of science to draw from.

Rest assured, though, this will not be the case for long. In part because ketone supplements could also enhance cognitive performance during exercise, these supplementation strategies have attracted quite a lot of attention from the military, not to mention national sporting federations.

Expect new research to roll in rapidly.

While the most obvious benefits of ketone supplementation (less glycogen usage and less lactate accumulation) are most relevant to marathoning and ultramarathoning, some research has found that ketone supplements could even improve performance in events as short as the 800 meters.

Experiments thus far usually involve taking ketones about half an hour before exercise, alongside water or a standard sports drink.

While ketones might also help with recovery, research so far is too preliminary to make any solid conclusions on the recovery front.

For now, ketones should be viewed as a promising but very much experimental supplement.

The potential payoff is pretty good—better endurance with less glycogen use and lower levels of lactate—but there is also a definite risk of gastrointestinal problems.

Until more research comes in, you can give ketone supplementation a shot, but make sure your stomach can handle it in a workout before you use it on race day.

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1. Burke, L.M., 2015. Re-examining high-fat diets for sports performance: did we call the ‘nail in the coffin’
too soon?. Sports Medicine, 45(1), pp.33-49.

2. Cox, P.J., Kirk, T., Ashmore, T., Willerton, K., Evans, R., Smith, A., Murray, A.J., Stubbs, B., West, J.,
McLure, S.W. and King, M.T., 2016. Nutritional ketosis alters fuel preference and thereby endurance
performance in athletes. Cell metabolism, 24(2), pp.256-268.

3. Stubbs, B.J., Koutnik, A.P., Poff, A.M., Ford, K.M. and D'Agostino, D.P., 2018. Commentary: ketone
diester ingestion impairs time-trial performance in professional cyclists. Frontiers in Physiology, 9,

4. Leckey, J.J., Ross, M.L., Quod, M., Hawley, J.A. and Burke, L.M., 2017. Ketone diester ingestion
impairs time-trial performance in professional cyclists. Frontiers in Physiology, 8, p.806.

5. Robinson, Melia, and Brodwin, Erin. The startup behind chewable coffee is launching a performance-
enhancing 'superhuman fuel' — we gave it a try. Business Insider, 2017.

6. Vandoorne, T., De Smet, S., Ramaekers, M., Van Thienen, R., De Bock, K., Clarke, K. and Hespel, P.,
2017. Intake of a ketone ester drink during recovery from exercise promotes mTORC1 signaling but not
glycogen resynthesis in human muscle. Frontiers in Physiology, 8, p.310.

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