Why Less Carbs Can Be Better For Cycling Performance?

If you’ve followed us for a while here at Fuel The Ride Academy, you’ll hopefully be aware of the important role that carbohydrates play in supporting cycling performance.

You’ll also have probably noticed that we talk about it a lot. This is largely because it is a fundamental aspect of diet for performance, and it’s also an area where athletes regularly get it wrong, often under fuelling as a result of poor nutrition knowledge (i.e. not understanding their needs) or in misguided approaches to weight loss.

Whilst fuelling is important when performance is key, you don’t always need to maximise glycogen stores ahead of every ride. In fact, taking on too much carbohydrate and having glycogen stores that are overly full may actually have a negative impact on performance. Let me explain.

For every gram of glycogen we store, we also store around 3-4 grams of water, as such, for a trained cyclist who can store in the region of 2000-2500 kcal of carbohydrate as glycogen, going from very low levels of glycogen to high levels of glycogen can potentially add over 2kg to your scale weight.

Fully topped-up glycogen stores are typically seen as enough fuel to get you through 90-120 minutes of high-intensity cycling exercise before glycogen stores begin to reach low levels, and fatigue starts to set in (fatigue often corresponds with a drop in glycogen to low levels). 

As such, if you’re doing an event that is shorter than that, or lower intensity, where you don’t need that amount of glycogen, the additional weight of that glycogen can negatively impact your power-to-weight ratio, particularly when this may be a key determinant of the event you’re taking part in (i.e. a hill climb). In the same way, you don’t need a full tank of fuel in your car to go a few miles down the road.

A 2023 study looked at exactly this (https://pubmed.ncbi.nlm.nih.gov/36932633/). They set out to see if lowered glycogen levels and the associated reduction in body weight would impact short-term high-intensity exercise performance of a cycling task that was 1 and 15 minutes in duration.

They put participants on a controlled diet to manipulate their pre-exercise glycogen levels of either 4 or 10 grams of carbohydrate per kilogram body weight, this was effective in creating around a 50% difference in glycogen levels between the two trials, but importantly, glycogen in the low trial wasn’t reduced to a level known to negatively impact performance.

 After completing the 1-minute and 15-minute maximal exercise tasks, there was no difference in performance, and the rating of perceived exertion was exactly the same in the two trials, but there was a 700-gram difference in weight between the trials, which could relate to a potentially meaningful impact on the power-to-weight ratio for a competitive athlete. So, in effect, when you don’t need full glycogen stores, having fewer carbohydrates on board may actually benefit exercise performance.

 When it comes to fuelling your training, the ultimate goal isn’t to have full glycogen stores and fuel every ride like a mountain stage of the Tour de France but to adjust your carbohydrate intake on a day-by-day, meal-by-meal basis to match the amount of fuel you are taking in with the demands of the training session or competition in which you are taking part. This is something we look to help you develop an understanding of within Fuel The Ride Academy.

 There are also other reasons why maximising glycogen stores at all times isn’t a good idea, from aspects of managing body composition to how excesses of muscle glycogen can negatively impact training adaptations, which we’ll cover in more detail in future blogs.

Coach Ben