During my PhD I did one particular study in which I had highly trained male athletes eat both a high carb diet and an ultra-low carbohydrate diet (similar to the ketogenic or Atkins diet) for 14 days. Two striking results came out of this study:
Firstly, if the participants were allowed a carbohydrate load the night before a 10km cycling Time Trial (TT) there was no difference in performance, regardless of diet. Neither the high carbohydrate nor the low carbohydrate/ketogenic diet stood out as the best choice. This was a big finding because the TT required the athletes to exercise above their anaerobic threshold. At this intensity carbohydrate is the main energy source used by the working muscles. This meant that despite eating less the 80g of carbohydrate per day the athletes were able to replenish their glycogen stores with just one day of carbohydrate loading, rather than the 3-4 days previously recommended.
Secondly, there was a massive shift in the fuels burnt by the athletes, both at rest and during exercise. In just 14 days the athletes were burning fat at rates that were that were similar to athletes on full-time low-carbohydrate diets (which I also researched in another study).
What I learnt from these results is that no matter how reliant on carbohydrate you are, just 14 days of dedicated carbohydrate restriction can induce rates of fat-burning which are similar to that of seasoned low carbers. This is shown visually in the image below of one participant I had in my study.
Note: This study involved two dietary interventions (low-carb or high-carb) followed by an exercise test in which participants completed with either a sports drink + ketone supplement or a sports drink only. The rationale behind this was to determine whether a ketone supplement could replicate the benefits of a carbohydrate-restricted diet. PLB = placebo, supp = ketone supplement
Short carbohydrate restriction protocols like this are currently been utilised by Pro Tour cyclists. At the 2016 European College of Sport Science conference, I attended a presentation by the Sky pro cycling team sport scientist. In his presentation he described how a ketogenic diet is applied for 10-14 days anywhere from 1-4 weeks out from big races to increase fat burning and body fat loss. After completing my own study in this area I can see why they’d use such as system.
If you’d like to try a low carbohydrate or ketogenic diet for yourself, I’ve written 7 day and 14 day plans that you can access via our online membership platform. Our platform comes with apple and android apps and includes running, triathlon and cycling training plans in addition to articles and videos. Once you’ve subscribed you can use these diet and training plans as much as you like which will allow you to figure out how and when a low carb or ketogenic may work best for you.
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If you’re interested in knowing more about low carbohydrate and ketogenic diets you can book a consultation with myself or Performance Advantage partner Dr Steve Stannard.
PhD Sport Scientist