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Ketones: What are they and do they improve performance?

Peter Stuart
13 Jul 2020

As it emerges British Cycling used ketone ester ahead of the 2012 Olympics, we look at history of the supplement

Ketones have been lauded as the new secret weapon in pro cycling, with rumours circulating for years of top teams using ketones in races at a cost of thousands of euros per bottle.

With the supplement coming into the mainstream and down in price, though, some now consider it a key necessity for high-end competition.

In recent days, it has emerged that British cyclists used ketones at the London 2012 Olympics as part of a trial for UK Sport. It raised questions of the ethics of experimental supplements, and also whether the supplement offered a benefit to athletes.

Last year, Belgian website Sporza reported that an advisor for Deceuninck-QuickStep, Professor Peter Hespel, had claimed that ketones were ‘a piece of the puzzle’ in QuickStep's fantastic success.

He went on to claim, ‘I think there are very few endurance athletes who don't know that something is happening with ketones and are already experimenting.’

This is not the first insider from the sport to discuss ketones, as ex-Team Sky member Greg Henderson discussed their suspected use in the team. He subsequently trialled the supplement and claimed enormous physiological gains.

While it would seem that ketones are becoming an open secret in pro cycling, and necessary to compete at elite level, first we need to clarify exactly what they are.

What are Ketones?

‘A ketone is another energy source,’ explains Kieran Clarke, Professor of Physiological Biochemistry at Oxford University, and inventor of the first ketone-based drink DeltaG. We spoke to Clarke in 2016, as part of a wider feature on legal performance-enhancing supplements.

A ketone is normally metabolised by the body to create energy, and originates from fats. ‘It's produced normally when you haven’t eaten or when you're on a kesogenic diet,’ Clarke explains. 

Clarke embarked on a project to create a way of ingesting ketones directly, rather than having to rely on the body to produce it from fat.

‘The research was originally funded by the research arm of the US army,’ she says. ‘They wanted somebody to invent a really efficient food and we said we could do that.’

The drink created by Clarke means that you can put ketones straight into your body that can be turned into energy. ‘It has similar effects to glucose and it works in the same way as glucose drinks, it provides energy for your muscles.’

Crucially, though, it has no discernable advantages over glucose. The main advantage, Clarke argues, is topping up your energy as your glycogen levels become depleted. ‘Things that last five or six hours will probably be the best use for it. But I think it depends on the individual, and it also depends how efficient they are at using their various substrates.’

Marginal or massive gains?

Professor Clarke sees no real advantages for the average athlete over glucose supplements and drinks.

‘If you have glucose by itself or ketones by itself, it’s not superior. It’s exactly the same – it’s just providing energy. For sprints glucose is better actually, because you need something that’s anaerobic,’ she says.

In response to rumours that athletes enjoy a 10% instant advantage at threshold pace when drinking a ketone ester, Clarke responds with restrained laughter: ‘No, I don’t think so! I think anyone who thinks that is having themselves on.’

However, ignoring claims of immediate threshold gains, the supplementation of ketones for an athlete with low fat and who has maxed out on carbohydrate and glucose intake in a race could be significant.

‘Once your glycogen is depleted you can't do anything about it,’ explains Clarke. ‘You're constantly topping up on glycogen when you're exercising. What they do mostly in the Tour de France is burn mainly fat, and glucose which they take in from drinks and gels.’

Eating enough to keep fat and carbohydrates in reserve is a better option in pure psychological terms, but the demands of racing mean that eating enough during competition isn’t always possible, or efficient.

It seems that if any pro teams are using ketone supplements, then, the gains are likely to be noticeable improvements in energy over longer stages, which in turn extends to speeding up recovery.

Will ketone supplements become standard amongst amateurs too, then?

Amateur hour

With the interaction of glucose, carbohydrates and ketones in mind, the use of ketones will only offer an advantage if an athlete's glucose and carbohydrate strategy is already perfected, which is a downside for those of us fading between food stops on a sportive.

For amateur enthusiasts, it’s also worth being extremely diligent about which ketones we buy. Raspberry ketones, for instance, are cheap and widely available but have a big downside.

‘Raspberry ketones which are not metabolised by the body,’ explains Clarke. Because they come from raspberries, they are only useful if you happen to be a raspberry.

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