By now you have likely heard of the keto (or HFLC) diet type being adopted by many in both the general and athletic population (sometimes falsely). However, as recent research attests, adaptation to a ketogenic diet can result in reduced exercise economy. What we mean by that is that you can actually be less efficient following a low carbohydrate diet, which is contrary to current popular belief.
To understand how ketone supplementation works, we must first explore what happens to the body when someone follows a low carb or keto diet.
In the absence of carbohydrates from the diet, the body is forced to produce its own fuel. These are known as ketones and are produced in the liver by breaking down fatty acids. Ketone bodies are essential because they are the only other type of fuel that will be used by the brain.
This is where the theory behind the possible value of exogenous (external) supplementation of ketone bodies (via ketone salts and esters) comes in. Is it possible to increase the levels of ketones without the strict adherence to a HFLC diet and the associated performance detriments?
Ketone esters (NOTE: Esters are different to the Ketone Salts that are much more readily available!) are split in the gut and taken into the blood, reaching peak concentrations in 1-2 hours.
Whether these ketones are used or not will then depend on which tissue it’s in (brain vs. muscle) and the athlete’s training status. Endurance based athletes are suggested to have a greater capacity to oxidise ketone bodies – so the higher trained athletes may be better prepped for ketone utilisation.
Also, if an athlete already has high levels of circulating ketones (e.g. if following a ketogenic diet), their muscles will be close to saturated and absorption will be reduced significantly.
Ketone supplementation may provide a more practical way for athletes to induce ketosis for a positive effect on performance. This may be due to:
Unfortunately, data from performance studies are currently extremely limited.
In terms of endurance performance, ketone bodies can be used as a fuel source for skeletal muscle. Theoretically, this means that muscle carbohydrate stores are spared for higher intensity efforts (more on this topic here).
However, this could also go the other way: by preventing the use of carbohydrates at lower intensities, you may also impede carbohydrate use at higher intensities – therefore lowering your performance capacity.
This leads to ketone supplementation likely being irrelevant in the vast majority of sporting endeavours that require high-intensity efforts or are of shorter duration. However, in sports such as triathlon, road cycling or endurance running, carbohydrate availability can be a limiting factor to performance, and therefore glycogen sparing may be of possible performance benefit.
ALICIA EDGE HEAD SPORTS DIETITIAN
Alicia is the head Advanced Sports Dietitian at Compeat Nutrition. She is also a mum and triathlete, so advice extends beyond the basics and is instead focused on providing effective and achievable nutrition for both training and racing.