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Should we be eating Keto?!

Updated: Nov 22, 2023




For all you sporty types on Keto in order to get leaner and lose body fat too – this ones for you! An interesting insight into how it could effect your performance.


Taking a little deeper look at a study from 2015 by Burke et al looking into the effects of a high fat diet on sports performance.


I like this one. The research looked at several studies examining participant adaption to low carb, high fat diets in order to increase fat utilisation during exercise and whether it could enhance physical performance by reducing their reliance on glycogen in the muscles.


The long and short of it is that after just 5 days, fat burning capacity in muscles increased and after 2-3 weeks, adaption was seen to a high ketone concentration in blood (essentially what happens when a person is in ketosis as part of undertaking a keto diet PROPERLY – note; a lot of people do not actually get into ketosis despite thinking that they are).

HOWEVER; let’s look at the effects of these adaptions –

  • There were no clear performance benefits in endurance and in fact impaired performance was seen in higher intensity exercise as a result of the down-regulation of carbohydrate metabolism so early on it already seems that perhaps the best approach as a nutritionist could be to promote individualised and periodised approaches promoting metabolic flexibility (essentially the optimal utilisation and ability to switch between utilisation of all different types of fuel within muscles) rather than merely a fat-based approach.


  • It was seen that the best approach would likely be to fuel periodically bearing in mind the demands of specific sessions, priorities within training sessions, nutrition requirements around competition and best promoting adaptive responses to training in order to support the muscles and the central nervous system – this is why it is important, if you’re serious about your performance, to work with a coach that understands this stuff and understands that optimal performance in any sport relies on adequate fuel stores relative to the individual and their sport.


  • It was, unsurprisingly, found that low carbohydrate availability can be associated with higher levels of fatigue – muscle glycogen needs to be utilised to support high rates of work.


  • It was found, albeit in a small sample of cyclists, that the increased fat utilisation seen can facilitate exercise in a state of ketosis over a number of days sub-maximally so it COULD be a fuelling method used in prolonged endurance events, however, this was seen at the expense of intensity so while it could be used it may be suggested that this isn’t the optimal strategy to implement.


  • They were able to conclude that when athletes had ‘trained’ their bodies to use fat more optimally as fuel it only takes a short time of a high fat, low carbohydrate diet for the body to ‘remember’ and begin to reutilise this ability for exercise of a moderate intensity.


  • On such high fat diets a reduction in training capacity, increased perceived exertion and an increased heart rate, especially where training was due to be of a high intensity or quality, was evident.

In order to be sure that these strategies are wise for athletes, marathon runners, triathletes, CrossFit athletes, with a performance focus we need more research of a good quality with the increased popularity of low carbohydrate, high fat intakes.


My favourite quote from the study sums it up perfectly for me as the information currently stands – ‘there should not be a choice of one fuel source or the other…but rather a desire to integrate and individualise the various dietary factors that can contribute to optimal sports performance’.


There is no one-size-fits-all solution – it’s important that, as an athlete, you work with a coach that understands and implements a number of strategies personal to the individual rather than being a zealot for one solution.


Peace and love as ever, A x




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